Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Shigekazu HIGUCHI Last modified date:2021.06.24

Professor / Physiological Anthropology / Department of Human Science / Faculty of Design

1. Taisuke Eto, Michihiro Ohashi, Kouaro Nagata, Nakyeong Shin, Yuki Motomura, Shigekazu Higuchi, Crystalline lens transmittance spectra and pupil sizes as factors affecting light-induced melatonin suppression in children and adults, OPHTHALMIC AND PHYSIOLOGICAL OPTICS, 10.1111/opo.12809, 2021.03.
2. Eto T,Petteri Teikari,Raymond P. Najjar,Nishimura Y,Motomura Y,Kuze M Higuchi S, A Purkinje image-based system for an assessment of the density and transmittance spectra of the human crystalline lens in vivo, scientific reports, 10.1038/s41598-020-73541-y, 2020.10, A method for rapid and objective assessment of ocular lens density and transmittance is needed for research and clinical practice. The aim of this study was to determine whether the Purkinje image-based technique can be used for objective and accurate quantification of spectral density and transmittance of ocular media (the mainly crystalline lens) in visible light. Twenty-six individuals (10 young, 9 middle-aged and 7 older individuals) participated in this study. Spectral lens density was evaluated by detecting the intensity of the IVth Purkinje image for different wavelengths. Subsequently, optical density index (ODI), the area under the curve in the lens density spectrum, was calculated and ODIs were compared with clinical lens opacification scales assessed subjectively using a slit lamp. Spectral lens transmittance was estimated from the lens density spectrum. Lens densities were higher in the short wavelength region of the visible spectrum across all age groups. ODI was highly correlated with the clinical opacification scale, while lens transmittance decreased with aging. Our results showed that spectral transmittance of the human crystalline lens can be easily estimated from optical density spectra evaluated objectively and rapidly using the Purkinje image-based technique. Our results provide clinicians and scientists with an accurate, rapid and objective technique for quantification of lens transmittance..
3. Sang Il Lee, Saki Kinoshita, Anna Noguchi, Taisuke Eto, Michihiro Ohashi, Yuki Nishimura, Kaho Maeda, Yuki Motomura, Yasuhiro Awata, Shigekazu Higuchi, Melatonin suppression during a simulated night shift in medium intensity light is increased by 10-minute breaks in dim light and decreased by 10-minute breaks in bright light, Chronobiology International, 10.1080/07420528.2020.1752704, 2020.01, Exposure to light at night results in disruption of endogenous circadian rhythmicity and/or suppression of pineal melatonin, which can consequently lead to acute or chronic adverse health problems. In the present study, we investigated whether exposure to very dim light or very bright light for a short duration influences melatonin suppression, subjective sleepiness, and performance during exposure to constant moderately bright light. Twenty-four healthy male university students were divided into two experimental groups: Half of them (mean age: 20.0 ± 0.9 years) participated in an experiment for short-duration (10 min) light conditions of medium intensity light (430 lx, medium breaks) vs. very dim light (< 1 lx, dim breaks) and the other half (mean age: 21.3 ± 2.5 years) participated in an experiment for short-duration light conditions of medium intensity light (430 lx, medium breaks) vs. very bright light (4700 lx, bright breaks). Each simulated night shift consisting of 5 sets (each including 50-minute night work and 10-minute break) was performed from 01:00 to 06:00 h. The subjects were exposed to medium intensity light (550 lx) during the night work. Each 10-minute break was conducted every hour from 02:00 to 06:00 h. Salivary melatonin concentrations were measured, subjective sleepiness was assessed, the psychomotor vigilance task was performed at hourly intervals from 21:00 h until the end of the experiment. Compared to melatonin suppression between 04:00 and 06:00 h in the condition of medium breaks, the condition of dim breaks significantly promoted melatonin suppression and the condition of bright breaks significantly diminished melatonin suppression. However, there was no remarkable effect of either dim breaks or bright breaks on subjective sleepiness and performance of the psychomotor vigilance task. Our findings suggest that periodic exposure to light for short durations during exposure to a constant light environment affects the sensitivity of pineal melatonin to constant light depending on the difference between light intensities in the two light conditions (i.e., short light exposure vs. constant light exposure). Also, our findings indicate that exposure to light of various intensities at night could be a factor influencing the light-induced melatonin suppression in real night work settings..
4. Yuki Ikeda, Yuki Nishimura, Nakyeong Shin, Shigekazu Higuchi, A study of EEG mu neurofeedback during action observation, Experimental Brain Research, 10.1007/s00221-020-05808-9, 238, 5, 1277-1284, 2020.05, The mirror system is a brain network that gets activated during action performance and observation. Brain mu waves have been used as a mirror system activity index; however, mu rhythm is prone to contamination by occipital alpha wave activity, thus raising a concern regarding its reliability as an index of the mirror system activity. In this study, we investigated whether mu suppression can be used as an index of neurofeedback training, which influences mirror system activities. Participants observed videos of hand movement under three different conditions: central mu feedback (muFB), occipital alpha feedback (aFB), and simple observation without any feedback (OBS). Results showed that at the 4–5 min mark, mu wave was most significantly suppressed in the central site at muFB. We thus demonstrated the possibility of increasing mu wave suppression in feedback training using a specific stimulus such as motion observation..
5. Sayuri Hayashi, Ayami Tsuru, Fumi Kishida, Kim YK, Shigekazu Higuchi, Yuki Motomura, ERP study on the associations of peripheral oxytocin and prolactin with inhibitory processes involving emotional distraction., Journal of Physiological Anthropology, 2019.05, Background:Child maltreatment is a major health and social welfare problem, with serious and longstanding consequences. Impulse control ability plays an important role in reducing the risk of child maltreatment. The aim of this study was to investigate the associations of oxytocin (OXT) and prolactin (PRL) with behavior inhibition using children's facial expressions (angry or neutral) as emotional distractions. This may clarify a part of the neuroendocrinological mechanism that modulates impulse control ability in the context of child caregiving..
6. Yuki Ikeda, Yuki Nishimura,Shigekazu Higuchi, Effects of the differences in mental states on the mirror system activities when observing hand actions, Journal of Physiological Anthropology, 2019.01, Background:It is known that the activities of the mirror system are related to imitation and understanding of the intention of an action. It has been reported that the activity of the mirror system is higher for observations for imitating and understanding the intention of an action than for simple observations. However, observations that facilitate the mirror system’s activities, if they are observations intending to imitate an action or observations for understanding the intention of an action, have not been clarified to date..
7. Sang‐il Lee,Kouhei Matsumori,Kana Nishimura,Yuki Nishimura,Yuki Ikeda,Taisuke Eto,Shigekazu Higuchi, Melatonin suppression and sleepiness in children exposed to blue‐enriched white LED lighting at night, Physiological Reports, 2018.12, Light‐induced melatonin suppression in children is reported to be more sensitive to white light at night than that in adults; however, it is unclear whether it depends on spectral distribution of lighting. In this study, we investigated the effects of different color temperatures of LED lighting on children's melatonin secretion during the night. Twenty‐two healthy children (8.9 ± 2.2 years old) and 20 adults (41.7 ± 4.4 years old) participated in this study. A between‐subjects design with four combinations, including two age groups (adults and children) and the two color temperature conditions (3000 K and 6200 K), was used. The experiment was conducted for two consecutive nights. On the first night, saliva samples were collected every hour under a dim light condition (<30 lx). On the second night, the participants were exposed to either color temperature condition. Melatonin suppression in children was greater than that in adults at both 3000 K and 6200 K condition. The 6200 K condition resulted in greater melatonin suppression than did the 3000 K condition in children (P < 0.05) but not in adults. Subjective sleepiness in children exposed to 6200 K light was significantly lower than that in children exposed to 3000 K light. In children, blue‐enriched LED lighting has a greater impact on melatonin suppression and it inhibits the increase in sleepiness during night. Light with a low color temperature is recommended at night, particularly for children's sleep and circadian rhythm..
8. Yuki Nishimura, Yuki Ikeda,Shigekazu Higuchi, The relationship between inhibition of automatic imitation and personal cognitive styles, Journal of Physiological Anthropology, 37, 24, 2018.10, Background:Previous studies have demonstrated the importance of the inhibition of automatic imitation in social interactions. Additionally, cognitive traits are known to vary among individuals. According to the empathizing-systemizing (E-S) model, personality can be quantified by empathizing and systemizing drives in causal cognition. Since inhibition of automatic imitation is strongly related to social cognition, the level of inhibition may be explained by personal cognitive traits. Thus, the current study tested whether cognitive traits, measured based on the E-S model, correlated with levels of automatic imitation inhibition..
9. 江藤太亮, 松森孝平, 李相逸,樋口重和, 瞳孔の対光反射のスペクトル感度に関する研究:児童と若年成人の比較, 日本生理人類学会誌, 23, 2, 63-67, 2018.06, Age-related decrease of crystalline lens transmittance is thought to be a factor affecting non-image forming (NIF) responses such as melatonin suppression and pupillary light reflex (PLR). In this study, we estimated pupillary spectral sensitivities of children and young adults and we compared them. Fourteen healthy primary school children and thirty healthy university students participated in the present study. The estimated spectral response curves tended to differ between the child group and the adult group (F-test, p &lt; 0.1), and their peak sensitivities were 474.2 nm and 479.7 nm, respectively. Our findings indicate that spectral sensitivity of PLR to light depends on age, supporting the possibility that age-related change in lens transmittance is associated with NIF responses. .
10. Yuki Nishimura ,Yuki Ikeda,Airi Suematsu and Shigekzau Higuchi , Effect of visual orientation on mu suppression in children: a comparative EEG study with adults, Journal of Physiological Anthropology, 37, 16, 2018.06, BACKGROUND: The human mirror neuron system exists in adults, and even in children. However, a significant, unanswered question in the literature concerns age differences in the effect of visual orientation of human body movements. The observation of actions performed by others is known to activate populations of neural cells called mirror neuron system. Moreover, the power of mu rhythms (8–13 Hz) in the EEG is known to decrease while performing and observing human movements. Therefore, the mu rhythm could be related to the activity of the mirror neuron system. This study investigated the effects of the visual perspective on electroencephalography responses to hand actions in two age groups..
11. Masakazu Okada,Masaaki Otaga,Takako Tsutsui,Hisateru Tachimori,Shingo Kitamura,Shigekazu Higuchi,Kazuo Mishima., Association of sleep with emotional and behavioral problems among abused children and adolescents admitted to residential care facilities in Japan, PLoS ONE, 2018.01, Background:
The psychological care of abused children in the child protection system is an urgent issue in Japan. Child abuse has a serious impact on children’s emotion and behavior, but there is virtually no evidence about how child abuse affects sleep, which is closely related to behavioral and emotional control. In this study, we sought to identify sleep habits and suspected sleep disorders among abused children and adolescents admitted to residential care facilities in Japan and to investigate their association with emotional and behavioral problems..
12. Sayuri Hayashi, Hiroko Wada, Sung Phil Kim, Yuki motomura, Shigekazu Higuchi, Yeon Kyu Kim, Enhanced Nogo-P3 amplitudes of mothers compared with non-mother women during an emotional Go/Nogo task, Journal of Physiological Anthropology, 10.1186/s40101-018-0167-9, 37, 1, 2018.04, BACKGROUND: It is known that emotion regulatory responses of humans are changed by the experiences they have, but in particular, they are changed by becoming a mother. A recent study has found how a woman's emotion regulatory response to a child's crying changes after becoming a mother. However, mothers' emotion regulatory responses other than those to children and the association between emotion regulatory response and parental stress are still unknown.
METHODS: Eighteen healthy Japanese females (nine mothers and nine non-mothers) participated in the experiment. They performed an emotional Go/Nogo task, with facial expressions of others (angry, happy, and neutral faces) used as emotional stimuli. The percentage of correct responses, response time, and event-related potentials (ERPs) during the task was measured.
RESULTS: This comparison revealed that the mother group had a larger P3 (Nogo-P3) amplitude than the non-mother group when Nogo trials were held. This indicates that in mothers, there was greater activation of the behavioral inhibition-related brain areas than in non-mother women when they inhibited inappropriate behavior following recognition of facial expressions of others. In addition, in the mother group, there was a negative correlation between parental stress levels and Nogo-P3 amplitudes evoked by angry faces. This suggests that there is a relation between the level of parental stress of mothers and their emotion regulatory responses to angry faces.
CONCLUSIONS: Our results demonstrate that mothers' emotion regulatory processes may differ from those of non-mothers in response, not only to a child's crying but also to expressions of emotions by others, and also suggest that the inhibitory recognition activity of mothers can be affected by parental stress..
13. Shinobu Yasuo, Ayaka Iwamoto, Sang Il Lee, Shotaro Ochiai, Rina Hitachi, Satomi Shibata, Nobuo Uotsu, Chie Tarumizu, Sayuri Matsuoka, Mitsuhiro Furuse, Shigekazu Higuchi, L-serine enhances light-induced circadian phase resetting in mice and humans, Journal of Nutrition, 10.3945/jn.117.255380, 147, 12, 2347-2355, 2017.12, Background: The circadian clock is modulated by the timing of ingestion or food composition, but the effects of specific nutrients are poorly understood. Objective: We aimed to identify the amino acids that modulate the circadian clock and reset the light-induced circadian phase in mice and humans. Methods: Male CBA/N mice were orally administered 1 of 20 L-amino acids, and the circadian and light-induced phase shifts of wheel-running activity were analyzed. Antagonists of several neurotransmitter pathways were injected before L-serine administration, and light-induced phase shifts were analyzed. In addition, the effect of L-serine on the light-induced phase advance was investigated in healthy male students (mean ± SD age 22.2 ± 1.8 y) by using dim-light melatonin onset (DLMO) determined by saliva samples as an index of the circadian phase. Results: L-Serine administration enhanced light-induced phase shifts inmice (1.86-fold; P < 0.05). Both L-serine and its metabolite D-serine, a coagonist of N-methyl-D-aspartic acid (NMDA) receptors, exerted this effect, but D-serine concentrations in the hypothalamus did not increase after L-serine administration. The effect of L-serine was blocked by picrotoxin, an antagonist of γ-aminobutyric acid A receptors, but not by MK801, an antagonist of NMDA receptors. L-Serine administration altered the long-term expression patterns of clock genes in the suprachiasmatic nuclei. After advancing the light-dark cycle by 6 h, L-serine administration slightly accelerated re-entrainment to the shifted cycle. In humans, L-serine ingestion before bedtime induced significantly larger phase advances of DLMO after bright-light exposure during the morning (means ± SEMs-L-serine: 25.9 ± 6.6 min; placebo: 12.1 ± 7.0 min; P < 0.05). Conclusion: These results suggest that L-serine enhances light-induced phase resetting in mice and humans, and it may be useful for treating circadian disturbances..
14. Masakazu Okada, Shingo Kitamura, Yoshitaka Iwadare, Hisateru Tachimori, Yuichi Kamei, Shigekazu Higuchi, Kazuo Mishima, Reliability and validity of a brief sleep questionnaire for children in Japan, Journal of Physiological Anthropology, 10.1186/s40101-017-0151-9, 36, 1, 2017.09, BACKGROUND: There is a dearth of sleep questionnaires with few items and confirmed reliability and validity that can be used for the early detection of sleep problems in children. The aim of this study was to develop a questionnaire with few items and assess its reliability and validity in both children at high risk of sleep disorders and a community population.
METHODS: Data for analysis were derived from two populations targeted by the Children's Sleep Habits Questionnaire (CSHQ): 178 children attending elementary school and 432 children who visited a pediatric psychiatric hospital (aged 6-12 years). The new questionnaire was constructed as a subset of the CSHQ.
RESULTS: The newly developed short version of the sleep questionnaire for children (19 items) had an acceptable internal consistency (0.65). Using the cutoff value of the CSHQ, the total score of the new questionnaire was confirmed to have discriminant validity (27.2 ± 3.9 vs. 22.0 ± 2.1, p < 0.001) and yielded a sensitivity of 0.83 and specificity of 0.78 by receiver operator characteristic curve analysis. Total score of the new questionnaire was significantly correlated with total score (r = 0.81, p < 0.001) and each subscale score (r = 0.29-0.65, p < 0.001) of the CSHQ.
CONCLUSIONS: The new questionnaire demonstrated an adequate reliability and validity in both high-risk children and a community population, as well as similar screening ability to the CSHQ. It could thus be a convenient instrument to detect sleep problems in children..
15. Tokiho Akiyama, Takafumi Katsumura, Shigeki Nakagome, Sang Il Lee, Keiichiro Joh, Hidenobu Soejima, Kazuma Fujimoto, Ryosuke Kimura, Hajime Ishida, Tsunehiko Hanihara, Akira Yasukouchi, Yoko Satta, Shigekazu Higuchi, Hiroki Oota, An ancestral haplotype of the human PERIOD2 gene associates with reduced sensitivity to light-induced melatonin suppression, PLoS One, 10.1371/journal.pone.0178373, 12, 6, 2017.06, Humans show various responses to the environmental stimulus in individual levels as physiological variations. However, it has been unclear if these are caused by genetic variations. In this study, we examined the association between the physiological variation of response to light-stimulus and genetic polymorphisms. We collected physiological data from 43 subjects, including light-induced melatonin suppression, and performed haplotype analyses on the clock genes, PER2 and PER3, exhibiting geographical differentiation of allele frequencies. Among the haplotypes of PER3, no significant difference in light sensitivity was found. However, three common haplotypes of PER2 accounted for more than 96% of the chromosomes in subjects, and 1 of those 3 had a significantly low-sensitive response to light-stimulus (P < 0.05). The homozygote of the low-sensitive PER2 haplotype showed significantly lower percentages of melatonin suppression (P < 0.05), and the heterozygotes of the haplotypes varied their ratios, indicating that the physiological variation for light-sensitivity is evidently related to the PER2 polymorphism. Compared with global haplotype frequencies, the haplotype with a low-sensitive response was more frequent in Africans than in non-Africans, and came to the root in the phylogenetic tree, suggesting that the low light-sensitive haplotype is the ancestral type, whereas the other haplotypes with high sensitivity to light are the derived types. Hence, we speculate that the high light-sensitive haplotypes have spread throughout the world after the Out-of-Africa migration of modern humans..
16. Kazuo Isoda, Kana Sueyoshi, Ryo Miyamoto, Yuki Nishimura, Yuki Ikeda, Ichiro Hisanaga, Stéphanie Orlic, Yeon kyu Kim, Shigekazu Higuchi, Tangible user interface and mu rhythm suppression
The effect of user interface on the brain activity in its operator and observer, Applied Sciences (Switzerland), 10.3390/app7040347, 7, 4, 2017.03, The intuitiveness of tangible user interface (TUI) is not only for its operator. It is quite possible that this type of user interface (UI) can also have an effect on the experience and learning of observers who are just watching the operator using it. To understand the possible effect of TUI, the present study focused on the mu rhythm suppression in the sensorimotor area reflecting execution and observation of action, and investigated the brain activity both in its operator and observer. In the observer experiment, the effect of TUI on its observers was demonstrated through the brain activity. Although the effect of the grasping action itself was uncertain, the unpredictability of the result of the action seemed to have some effect on the mirror neuron system (MNS)-related brain activity. In the operator experiment, in spite of the same grasping action, the brain activity was activated in the sensorimotor area when UI functions were included (TUI). Such activation of the brain activity was not found with a graphical user interface (GUI) that has UI functions without grasping action. These results suggest that the MNS-related brain activity is involved in the effect of TUI, indicating the possibility of UI evaluation based on brain activity..
17. Kazuo Isoda, Kana Sueyoshi, Yuki Ikeda, Yuki Nishimura, Ichiro Hisanaga, Stéphanie Orlic, Yeon Kyu Kim, Shigekazu Higuchi, Effect of the hand-omitted tool motion on mu rhythm suppression, Frontiers in Human Neuroscience, 10.3389/fnhum.2016.00266, 10, 2016.06, In the present study, we investigated the effect of the image of hands on mu rhythm suppression invoked by the observation of a series of tool-based actions in a goal-directed activity. The participants were 11 university students. As a source of visual stimuli to be used in the test, a video animation of the porcelain making process for museums was used. In order to elucidate the effect of hand imagery, the image of hands was omitted from the original (“hand image included”) version of the animation to prepare another (“hand image omitted”) version. The present study has demonstrated that, an individual watching an instructive animation on the porcelain making process, the image of the porcelain maker’s hands can activate the mirror neuron system (MNS). In observations of “tool included” clips, even the “hand image omitted” clip induced significant mu rhythm suppression in the right central area. These results suggest that the visual observation of a tool-based action may be able to activate the MNS even in the absence of hand imagery..
18. Shigekazu Higuchi, Sang Il Lee, Tomoaki Kozaki, Tetsuo Harada, Ikuo Tanaka, Late circadian phase in adults and children is correlated with use of high color temperature light at home at night, Chronobiology International, 10.3109/07420528.2016.1152978, 33, 4, 448-452, 2016.04, Light is the strongest synchronizer of human circadian rhythms, and exposure to residential light at night reportedly causes a delay of circadian rhythms. The present study was conducted to investigate the association between color temperature of light at home and circadian phase of salivary melatonin in adults and children. Twenty healthy children (mean age: 9.7 year) and 17 of their parents (mean age: 41.9 years) participated in the experiment. Circadian phase assessments were made with dim light melatonin onset (DLMO). There were large individual variations in DLMO both in adults and children. The average DLMO in adults and in children were 21:50 ± 1:12 and 20:55 ± 0:44, respectively. The average illuminance and color temperature of light at eye level were 139.6 ± 82.7 lx and 3862.0 ± 965.6 K, respectively. There were significant correlations between color temperature of light and DLMO in adults (r = 0.735, p < 0.01) and children (r = 0.479, p < 0.05), although no significant correlations were found between illuminance level and DLMO. The results suggest that high color temperature light at home might be a cause of the delay of circadian phase in adults and children..
19. Yosuke Kaneshi, Hidenobu Ohta, Keita Morioka, Itaru Hayasaka, Yutaka Uzuki, Takuma Akimoto, Akinori Moriichi, Machiko Nakagawa, Yoshihisa Oishi, Hisanori Wakamatsu, Naoki Honma, Hiroki Suma, Ryuichi Sakashita, Sei Ichi Tsujimura, Shigekazu Higuchi, Miyuki Shimokawara, Kazutoshi Cho, Hisanori Minakami, Influence of light exposure at nighttime on sleep development and body growth of preterm infants, Scientific Reports, 10.1038/srep21680, 6, 2016.02, Previous studies have demonstrated that a light-dark cycle has promoted better sleep development and weight gain in preterm infants than constant light or constant darkness. However, it was unknown whether brief light exposure at night for medical treatment and nursing care would compromise the benefits brought about by such a light-dark cycle. To examine such possibility, we developed a special red LED light with a wavelength of >675 nm which preterm infants cannot perceive. Preterm infants born at <36 weeks' gestational age were randomly assigned for periodic exposure to either white or red LED light at night in a light-dark cycle after transfer from the Neonatal Intensive Care Unit to the Growing Care Unit, used for supporting infants as they mature. Activity, nighttime crying and body weight were continuously monitored from enrolment until discharge. No significant difference in rest-activity patterns, nighttime crying, or weight gain was observed between control and experimental groups. The data indicate that nursing care conducted at 3 to 4-hour intervals exposing infants to light for <15 minutes does not prevent the infants from developing circadian rest-activity patterns, or proper body growth as long as the infants are exposed to regular light-dark cycles..
20. Ogawa M, Seno T, Matsumori K, Higuchi S, Twenty-Hour Sleep Deprivation Does Not Affect Perceived Vection Strength, J Behav Brain Sci, 10.4236/jbbs.2015.512052, 5, 12, 550-560, 2015.11, [URL].
21. Kosuke Zaitsu, Yuki Nishimura, Hiroyuki Matsuguma, Shigekazu Higuchi, Association between Extraversion and Exercise Performance among Elderly Persons Receiving a Videogame Intervention, Games for health journal, 10.1089/g4h.2014.0119, 4, 5, 375-380, 2015.10, Objective: We examined the effects of an exergame intervention on exercise performance, as well as the influence of players' personality traits on the effects of the intervention. Materials and Methods: In total, 16 elderly persons (>65 years old) participated in the study for 12 weeks. Participants were required to complete the Big Five Scale. We measured the number of times that the sit-to-stand exercise was performed during the interventions with and without exergames. Results: We compared the average number of times that the sit-to-stand exercise was performed per day in each of the two conditions. The average number of times that exercise was undertaken with exergame use was greater than that without exergame use; however, no significant difference was found. The difference between the average number of times that exercise occurred with and without exergame use was positively correlated with neuroticism, negatively correlated with extraversion, and not associated with conscientiousness. Conclusions: The intervention comprising the use of exergames has a positive motivational influence among less extraverted elderly persons..
22. Jakub Spati, Sayaka Aritake, Andrea H. Meyer, Shingo Kitamura, Akiko Hida, Shigekazu Higuchi, Yoshiya Moriguchi, Kazuo Mishima, Modeling circadian and sleep-homeostatic effects on short-term interval timing, Frontiers in Integrative Neuroscience, 10.3389/fnint.2015.00015, 9, FEB, 1-9, 2015.02, Short-term interval timing i.e., perception and action relating to durations in the seconds range, has been suggested to display time-of-day as well as wake dependent fluctuations due to circadian and sleep-homeostatic changes to the rate at which an underlying pacemaker emits pulses; pertinent human data being relatively sparse and lacking in consistency however, the phenomenon remains elusive and its mechanism poorly understood. To better characterize the putative circadian and sleep-homeostatic effects on interval timing and to assess the ability of a pacemaker-based mechanism to account for the data, we measured timing performance in eighteen young healthy male subjects across two epochs of sustained wakefulness of 38.67 h each, conducted prior to (under entrained conditions) and following (under free-running conditions) a 28 h sleep-wake schedule, using the methods of duration estimation and duration production on target intervals of 10 and 40 s. Our findings of opposing oscillatory time courses across both epochs of sustained wakefulness that combine with increasing and, respectively, decreasing, saturating exponential change for the tasks of estimation and production are consistent with the hypothesis that a pacemaker emitting pulses at a rate controlled by the circadian oscillator and increasing with time awake determines human shortterm interval timing; the duration-specificity of this pattern is interpreted as reflecting challenges to maintaining stable attention to the task that progressively increase with stimulus magnitude and thereby moderate the effects of pacemaker-rate changes on overt behavior..
23. Shigekazu Higuchi, Yuki Nagafuchi, Sang Il Lee, Tetsuo Harada, Influence of light at night on melatonin suppression in children, Journal of Clinical Endocrinology and Metabolism, 10.1210/jc.2014-1629, 99, 9, 3298-3303, 2014.09, Context: The sensitivity of melatonin to light suppression is expected to be higher in children because children have large pupilsandpure crystal lenses. However, melatonin suppression by light in children remains unclear. Copyright
Objective: We investigated whether light-induced melatonin suppression in children is larger than that in adults.
Methods: Thirty-three healthy primary school children(meanage, 9.2±1.5 y)and29 healthy adults (meanage, 41.6±4.7 y) participated intwoexperiments. In the first experiment, salivary melatonin concentrations in 13 children and 13 adults were measured at night under a dim light (<30 lux) and a moderately bright light (580 lux) in an experimental facility. Pupil diameters were also measured under dim light and bright light. In the second experiment, melatonin concentrations in 20 children and 16 adults were measured under dim light in the experimental facility and under room light at home (illuminance, 140.0 ± 82.7 lux).
Results: In experiment 1, the melatonin concentration was significantly decreased by exposure to moderately bright light in both adults and children. Melatonin suppression was significantly larger in children (88.2%; n = 5) than in adults (46.3%; n = 6; P < .01), although the data for some participants were excluded because melatonin concentrations had not yet risen. In experiment 2, melatonin secretion was significantly suppressed by room light at home in children (n = 15; P < .05) but not in adults (n = 11).
Conclusion: We found that the percentage of melatonin suppression by light in children was almost twice that in adults, suggesting that melatonin is more sensitive to light in children than in adults at night..
24. Yuki motomura, Shingo Kitamura, Kentaro Oba, Yuri Terasawa, Minori Enomoto, Yasuko Katayose, Akiko Hida, Yoshiya Moriguchi, Shigekazu Higuchi, Kazuo Mishima, Sleepiness induced by sleep-debt enhanced amygdala activity for subliminal signals of fear, BMC Neuroscience, 10.1186/1471-2202-15-97, 15, 1, 2014.08, Background: Emotional information is frequently processed below the level of consciousness, where subcortical regions of the brain are thought to play an important role. In the absence of conscious visual experience, patients with visual cortex damage discriminate the valence of emotional expression. Even in healthy individuals, a subliminal mechanism can be utilized to compensate for a functional decline in visual cognition of various causes such as strong sleepiness. In this study, sleep deprivation was simulated in healthy individuals to investigate functional alterations in the subliminal processing of emotional information caused by reduced conscious visual cognition and attention due to an increase in subjective sleepiness. Fourteen healthy adult men participated in a within-subject crossover study consisting of a 5-day session of sleep debt (SD, 4-h sleep) and a 5-day session of sleep control (SC, 8-h sleep). On the last day of each session, participants performed an emotional face-viewing task that included backward masking of nonconscious presentations during magnetic resonance scanning. Results: Finally, data from eleven participants who were unaware of nonconscious face presentations were analyzed. In fear contrasts, subjective sleepiness was significantly positively correlated with activity in the amygdala, ventromedial prefrontal cortex, hippocampus, and insular cortex, and was significantly negatively correlated with the secondary and tertiary visual areas and the fusiform face area. In fear-neutral contrasts, subjective sleepiness was significantly positively correlated with activity of the bilateral amygdala. Further, changes in subjective sleepiness (the difference between the SC and SD sessions) were correlated with both changes in amygdala activity and functional connectivity between the amygdala and superior colliculus in response to subliminal fearful faces.Conclusion: Sleepiness induced functional decline in the brain areas involved in conscious visual cognition of facial expressions, but also enhanced subliminal emotional processing via superior colliculus as represented by activity in the amygdala. These findings suggest that an evolutionally old and auxiliary subliminal hazard perception system is activated as a compensatory mechanism when conscious visual cognition is impaired. In addition, enhancement of subliminal emotional processing might cause involuntary emotional instability during sleep debt through changes in emotional response to or emotional evaluation of external stimuli..
25. Kenta Hayashida, Shigekazu Higuchi, Jiro Kajiwara, Sang il Lee, Kenji Kai, Katsuyoshi Setsu, Fumitada Hattori, Nighttime sleep is correlated with effectiveness of inpatient rehabilitation for hemiplegia patients after stroke, Sleep and Biological Rhythms, 10.1111/sbr.12079, 12, 3, 220-223, 2014.07, The purpose of the present study was to clarify the relationship between nighttime sleep and effectiveness of inpatient rehabilitation for stroke patients during convalescence. Fifteen patients participated. Nighttime sleep was measured by actigraph recording. Actual sleep time was significantly correlated with discharge motor Functional Independence Measure (FIM) score and FIM efficiency. Wake after sleep onset (WASO) time was significantly correlated with length of stay. Sleep efficiency was significantly correlated with discharge motor FIM score. Our study showed a relationship between nighttime sleep and effectiveness of inpatient rehabilitation during convalescence after stroke..
26. Sang Il Lee, Akiko Hida, Shingo Kitamura, Kazuo Mishima, Shigekazu Higuchi, Association between the melanopsin gene polymorphism OPN4*Ile394Thr and sleep/wake timing in Japanese university students, Journal of Physiological Anthropology, 10.1186/1880-6805-33-9, 33, 1, 2014.06, Background: In our previous studies, we found that the Ile394Thr SNP in the melanopsin gene (OPN4) was functionally associated with the pupillary light reflex. This indicates the possibility that OPN4*Ile394Thr is associated with other non-image forming responses. The aim of this study was therefore to determine whether OPN4*Ile394Thr is associated with sleep/wake timing. Methods: A total of 348 healthy Japanese university students participated in this study. Scalp hair was used to genotype the Ile394Thr SNP of OPN4. Sleep habits, including bedtime, wake time and sleep duration, were assessed separately for weekdays and weekends. A total of 328 samples, including 223 samples with TT genotype, 91 with TC genotype and 14 with CC genotype, were used for statistical analysis. No significant difference in age or male/ female distribution was found among the three genotype groups. Results: There was no significant difference in circadian preference among the genotype groups. During weekdays, bedtime, wake time and midpoint of sleep for CC subjects were significantly later than those for TT and TC subjects. However, there was no difference between TT and TC subjects in any of their sleep habits. During weekends, bedtime of CC subjects was significantly later than those of TT and TC subjects, and the midpoint of sleep of CC subjects was significantly later than that of TC subjects. Conclusions: Our findings demonstrated that OPN4*Ile394Thr is associated with sleep/wake timing. We also found that the sleep/wake timing of subjects with the CC genotype was later than that of subjects with the TT or TC genotype..
27. Kosuke Zaitsu, Kenta Hayashida, Jiro Kajiwara, Hiroyuki Matsuguma, Shigekazu Higuchi, Evaluation of the physiological and psychological effects of video game for sit to stand exercise, Japanese Journal of Physical Fitness and Sports Medicine, 10.7600/jspfsm.63.469, 63, 5, 469-473, 2014.01, The purpose of this study was to investigate the physiological and psychological effects of sit to stand exercise using a video game. Twelve young male adults performed sit to stand exercise with a video game and without a video game. Heart rate, oxygen consumption (V4 O2), electromyogram of lower limbs (%MVC) and perceived exertion (RPE) were measured during exercise. Mood states (POMS) were measured before and after exercise. There were no significant differences in physiological measurements between the two conditions. On the other hand, depression scale was significantly decreased after exercise only in the game condition. These results suggest that sit to stand exercise with a video game may have positive psychological effects without change in physiological load compared to the same exercise without a video game..
28. Shingo Kitamura, Akiko Hida, Sayaka Aritake, Shigekazu Higuchi, Minori Enomoto, Mie Kato, Céline Vetter, Till Roenneberg, Kazuo Mishima, Validity of the Japanese version of the Munich ChronoType Questionnaire, Chronobiology International, 10.3109/07420528.2014.914035, 31, 7, 845-850, 2014.01, To assess circadian preference with a score, the Morningness-Eveningness Questionnaire (MEQ) has been used for more than 3 decades now. More recently, the Munich ChronoType Questionnaire (MCTQ) was developed: it asks for sleep-wake behavior on work and free days and uses the midpoint of sleep on free days (MSF), corrected for sleep debt accumulated during the work week as an indicator of chronotype (MSFsc). In this study, we developed a Japanese version of the MCTQ by using a translation/back-translation approach including an examination of its semantic validity. In a subsequent questionnaire survey, 450 adult men and women completed the Japanese versions of the MCTQ and MEQ. Results showed that MEQ scores were significantly negatively correlated with mid-sleep parameters assessed by the MCTQ, on both, work and free days, as well as with the chronotype measure MSFsc (r = -0.580 to -0.652, all p < 0.001). As in the original German version, the strongest correlation was observed between MEQ score and MSF. A physiological validation study using dim light melatonin onset as a circadian phase marker (N = 37) showed a high correlation between chronotype as assessed with the MSFsc (r = 0.542, p < 0.001), and less so for MEQ score (r = -0.402, p = 0.055). These results demonstrate the validity of the Japanese MCTQ and provide further support of the adequacy of the MCTQ as a chronotype measure..
29. Sang il Lee, Akiko Hida, Sei ichi Tsujimura, Takeshi Morita, Kazuo Mishima, Shigekazu Higuchi, Association between melanopsin gene polymorphism (I394T) and pupillary light reflex is dependent on light wavelength, Journal of Physiological Anthropology, 10.1186/1880-6805-32-16, 32, 1, 2013.10, Background: Our aim was to determine the association between melanopsin gene polymorphism and pupillary light reflex under diverse photic conditions, including different intensities and wavelengths.Methods: A total of 195 visually corrected subjects volunteered for investigation of the melanopsin gene of single nucleotide polymorphism (SNP) of rs1079610 (I394T). The genotype groups were TT (n = 126), TC (n = 55), and CC (n = 8), and 75 of the subjects, including subjects with TT (n = 34), TC (n = 33), and CC (n = 8) participated in our experiment. Three monochromatic lights with peak wavelengths of 465 nm (blue), 536 nm (green), and 632 nm (red) were prepared, and each light was projected to the subjects with five intensities, 12, 13, 14, 14.5 and 15 log photons/(cm2 s), for one minute. The pupil size of the left eye was measured under each light condition after a 1-minute adaptation.Results: The pupils of the TC + CC genotypes (n = 38) were significantly smaller than those of the TT genotype (n = 31) under a blue (463 nm) light condition with 15 log photons/(cm2 s) (P < 0.05). In contrast, there were no significant differences under green (536 nm) and red (632 nm) light conditions. Conversely, relative pupil constrictions of the TC + CC genotypes were greater than those of the TT genotype under both blue and green conditions with high intensities (14.5 and 15 log photons/(cm2 s)). In contrast, there were no significant differences between genotype groups in pupil size and relative pupilloconstriction under the red light conditions.Conclusions: Our findings suggest that the melanopsin gene polymorphism (I394T) functionally interacts with pupillary light reflex, depending on light intensity and, particularly, wavelength, and that under a light condition fulfilling both high intensity and short wavelength, the pupillary light response of subjects with the C allele (TC + CC) is more sensitive to light than that of subjects with the TT genotype..
30. Akiko Hida, Shingo Kitamura, Yosuke Ohsawa, Minori Enomoto, Yasuko Katayose, Yuki motomura, Yoshiya Moriguchi, Kentaro Nozaki, Makiko Watanabe, Sayaka Aritake, Shigekazu Higuchi, Mie Kato, Yuichi Kamei, Shin Yamazaki, Yu Ichi Goto, Masaaki Ikeda, Kazuo Mishima, In vitro circadian period is associated with circadian/sleep preference, Scientific Reports, 10.1038/srep02074, 3, 2013.06, Evaluation of circadian phenotypes is crucial for understanding the pathophysiology of diseases associated with disturbed biological rhythms such as circadian rhythm sleep disorders (CRSDs). We measured clock gene expression in fibroblasts from individual subjects and observed circadian rhythms in the cells (in vitro rhythms). Period length of the in vitrorhythm (in vitroperiod) was compared with the intrinsic circadian period, τ, measured under a forced desynchrony protocol (in vivoperiod) and circadian/sleep parameters evaluated by questionnaires, sleep log, and actigraphy. Although no significant correlation was observed between the in vitroand in vivoperiods, the in vitroperiod was correlated with chronotype, habitual sleep time, and preferred sleep time. Our data demonstrate that thein vitroperiod is significantly correlated with circadian/sleep preference. The findings suggest that fibroblasts from individual patients can be utilized for in vitroscreening of therapeutic agents to provide personalized therapeutic regimens for CRSD patients..
31. Shigekazu Higuchi, Akiko Hida, Sei Ichi Tsujimura, Kazuo Mishima, Akira Yasukouchi, Sang Il Lee, Youhei Kinjyo, Manabu Miyahira, Melanopsin Gene Polymorphism I394T Is Associated with Pupillary Light Responses in a Dose-Dependent Manner, PLoS One, 10.1371/journal.pone.0060310, 8, 3, 2013.03, Background: Melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) play an important role in non-image forming responses to light, such as circadian photoentrainment, light-induced melatonin suppression, and pupillary light response. Although it is known that there are some single nucleotide polymorphisms (SNPs) in the melanopsin (OPN4) gene in humans, the associations of the SNPs with non-image forming responses to light remains unclear. In the present study, we examined the associations of melanopsin gene polymorphisms with pupillary light response. Methods: Japanese university students (mean age: 21.0±1.7 years) with the genotypes of TT (n = 38), TC (n = 28) and CC (n = 7) at rs1079610 (I394T) located in the coding region participated in the present study. They were matched by age and sex ratio. Dark-adapted pupil size (<1 lx) was first measured. Then steady-state pupil size was measured during exposure to five lighting conditions (10 lx, 100 lx, 1000 lx, 3000 lx, 6000 lx in the vertical direction at eye level). Results: Significant interaction between the genotype of I394T (TT versus TC+CC) and luminance levels was found in pupil size. Under high illuminance levels (1000 lx, 3000 lx and 6000 lx), pupil sizes in subjects with the C allele were significantly smaller than those in subjects with the TT genotype. On the other hand, pupil size in subjects with the C allele under low illuminance (<1 lx) was significantly larger than that in subjects with the TT genotype. Percentages of pupil constriction under high illuminance levels were significantly greater in subjects with the C allele than in subjects with the TT genotype. Conclusions: Human melanopsin gene polymorphism I394T interacted with irradiance in association with pupil size. This is the first evidence suggesting a functional connection between melanopsin gene polymorphism and pupillary light response as an index of non-image forming response to light..
32. Yuki motomura, Shingo Kitamura, Kentaro Oba, Yuri Terasawa, Minori Enomoto, Yasuko Katayose, Akiko Hida, Yoshiya Moriguchi, Shigekazu Higuchi, Kazuo Mishima, Sleep Debt Elicits Negative Emotional Reaction through Diminished Amygdala-Anterior Cingulate Functional Connectivity, PLoS One, 10.1371/journal.pone.0056578, 8, 2, 2013.02, Objectives: Sleep debt reportedly increases emotional instability, such as anxiety and confusion, in addition to sleepiness and psychomotor impairment. However, the neural basis of emotional instability due to sleep debt has yet to be elucidated. This study investigated changes in emotional responses that are elicited by the simulation of short-term sleep loss and the brain regions responsible for these changes. Subjects and Methods: Fourteen healthy adult men aged 24.1±3.3 years (range, 20-32 years) participated in a within-subject crossover study consisting of 5-day sessions of both sleep debt (4 h for time in bed) and sleep control (8 h for time in bed). On the last day of each session, participants underwent polysomnography and completed the State-Trait Anxiety Inventory and Profile of Mood States questionnaires. In addition, functional magnetic resonance imaging was conducted while performing an emotional face viewing task. Results: Restricted sleep over the 5-day period increased the activity of the left amygdala in response to the facial expression of fear, whereas a happy facial expression did not change the activity. Restricted sleep also resulted in a significant decrease in the functional connectivity between the amygdala and the ventral anterior cingulate cortex (vACC) in proportion to the degree of sleep debt (as indicated by the percentage of slow wave sleep and δ wave power). This decrease was significantly correlated with activation of the left amygdala and deterioration of subjective mood state. Conclusion: The results of this study suggest that continuous and accumulating sleep debt that can be experienced in everyday life can downregulate the functional suppression of the amygdala by the vACC and consequently enhance the response of the amygdala to negative emotional stimuli. Such functional alteration in emotional control may, in part, be attributed to the neural basis of emotional instability during sleep debt..
33. Miyuki Tamura, Yoshiya Moriguchi, Shigekazu Higuchi, Akiko Hida, Minori Enomoto, Jun Umezawa, Kazuo Mishima, Activity in the action observation network enhances emotion regulation during observation of risk-taking
An fMRI study, Neurological Research, 10.1179/1743132812Y.0000000109, 35, 1, 22-28, 2013.01, Objectives: The results of neuroimaging studies have indicated that viewing emotional stimuli can lead to activity increases in brain regions associated with processing actions. We hypothesized that observation of actions involving the potential for harm (i.e., risk-taking actions) would activate emotion- and pain-relatedprocessing. Methods: We used functional magnetic resonance imaging to examine the changes in neural activity during the observation of safe and risk-taking actions in 34 healthy participants (14 females, 20 males; mean age: 23.4+3.7 years). Results: Observation of risk-taking actions elicited significantly stronger neural activation in the inferior frontal gyrus, ventromedial prefrontal cortex, superior frontal gyrus/frontal pole, inferior parietal lobule, middle temporal gyrus, middle occipital gyrus, lingual gyrus, cuneus (including the calcarine sulcus), insula, and amygdala, than observation of safe actions. Interestingly, we observed significant activation of affect-related brain areas (ventromedial prefrontal cortex, amygdala, and insula), thought to be implicated in various aspects of emotion regulation during the observation of risk-taking actions. No brain regions exhibited greater activation during observation of safe actions than during observation of risk-taking actions associated with risk. Discussion: Our results reveal that the risk-related content of the observed actions in the video clips elicited activation of a network of visual input and processing regions, including the action observation network, that appears to encode the meanings of observed actions as well as the reflective or retrospective monitoring of their outcomes. These findings suggest that risk-taking situations may increase cognitive load on the entire action perception system, and may command more attention..
34. Shingo Kitamura, Akiko Hida, Minori Enomoto, Makiko Watanabe, Yasuko Katayose, Kentaro Nozaki, Sayaka Aritake, Shigekazu Higuchi, Yoshiya Moriguchi, Yuichi Kamei, Kazuo Mishima, Intrinsic circadian period of sighted patients with circadian rhythm sleep disorder, free-running type, Biological Psychiatry, 10.1016/j.biopsych.2012.06.027, 73, 1, 63-69, 2013.01, Background: Circadian rhythm sleep disorder, free-running type (FRT), is an intractable sleep disorder in which sleep and wake times progressively delay each day even in normal living environments. This disorder severely affects the social functioning of patients because of periodic nighttime insomnia, excessive daytime sleepiness, and a high rate of comorbid psychiatric disorders. Although abnormal regulation of the biological clock is suspected, the pathophysiology of FRT has yet to be elucidated. In this study, the endogenous circadian period, τ, of FRT patients with normal vision was compared with that of healthy individuals whose circadian rhythms are entrained to a 24-hour cycle. Methods: Six FRT patients and 17 healthy individuals (9 intermediate chronotypes and 8 evening chronotypes) were subjected to a 7-day, 28-hour sleep-wake schedule according to the forced desynchrony protocol. Phase shifts in melatonin rhythm were measured under constant routine conditions to calculate τ. Results: In FRT patients, τ was significantly longer than in intermediate chronotypes, whereas in evening chronotypes, it ranged widely and was not significantly different from that in FRT patients. Moreover, τ of melatonin rhythm in FRT patients showed no significant correlation with τ of sleep-wake cycles measured before the study. Conclusions: The findings suggest that although a prolongation of τ may be involved in the onset mechanism of FRT, a prolonged τ is not the only factor involved. It appears that several factors including abnormal entrainment of circadian rhythms are involved in the onset of FRT in a multilayered manner..
35. Keita Ishibashi, Takafumi Maeda, Shigekazu Higuchi, Koichi Iwanaga, Akira Yasukouchi, Comparison of cardiovascular response to sinusoidal and constant lower body negative pressure with reference to very mild whole-body heating., Journal of Physiological Anthropology, 10.1186/1880-6805-31-30, 31, 2012.12, The purpose of the present study was to compare sinusoidal versus constant lower body negative pressure (LBNP) with reference to very mild whole-body heating. Sinusoidal LBNP has a periodic load component (PLC) and a constant load component (CLC) of orthostatic stress, whereas constant LBNP has only a CLC. We tested two sinusoidal patterns (30-s and 180-s periods with 25 mmHg amplitude) of LBNP and a constant LBNP with -25 mmHg in 12 adult male subjects. Although the CLC of all three LBNP conditions were configured with -25 mmHg, the mean arterial pressure (MAP) results showed a significantly large decrease from baseline in the 30-s period condition (P <0.01). In contrast, the other cardiovascular indices (heart rate (HR), stroke volume (SV), cardiac output (CO), basal thoracic impedance (Z(0)), total peripheral resistance (TPR), the natural logarithmic of the HF component (lnHF), and LF/HF (ln(LF/HF))) of heart rate variability (HRV) showed relatively small variations from baseline in the 30-s period condition (P <0.01). The result of the gain and phase of transfer function at the sinusoidal period of LBNP showed that the very mild whole-body heating augmented the orthostatic responses. These results revealed that the effect of the CLC of LBNP on cardiovascular adjustability was attenuated by the addition of the PLC to LBNP. Based on the results of suppressed HRV response from baseline in the 30-s period condition, we suggest that the attenuation may be caused by the suppression of the vagal responsiveness to LBNP..
36. Sayaka Aritake, Shigekazu Higuchi, Hiroyuki Suzuki, Kenichi Kuriyama, Minori Enomoto, Takahiro Soshi, Shingo Kitamura, Akiko Hida, Kazuo Mishima, Increased cerebral blood flow in the right frontal lobe area during sleep precedes self-awakening in humans, BMC Neuroscience, 10.1186/1471-2202-13-153, 13, 1, 2012.12, Background: Some people can subconsciously wake up naturally (self-awakening) at a desired/planned time without external time stimuli. However, the underlying mechanism regulating this ability remains to be elucidated. This study sought to examine the relationship between hemodynamic changes in oxyhemoglobin (oxy-Hb) level in the prefrontal cortex and sleep structures during sleep in subjects instructed to self-awaken.Results: Fifteen healthy right-handed male volunteers with regular sleep habits participated in a consecutive two-night crossover study. The subjects were instructed to wake up at a specified time (" request" condition) or instructed to sleep until the morning but forced to wake up at 03:00 without prior notice (" surprise" condition). Those who awoke within ± 30 min of the planned waking time were defined as those who succeeded in self-awakening (" success" group). Seven subjects succeeded in self-awakening and eight failed.No significant differences were observed in the amounts of sleep in each stage between conditions or between groups. On the " request" night, an increase in oxy-Hb level in the right prefrontal cortex and a decrease in δ power were observed in the " success" group around 30 min before self-awakening, whereas no such changes were observed in the " failure" group. On the " surprise" night, no significant changes were observed in oxy-Hb level or δ power in either group.Conclusions: These findings demonstrate a correlation between self-awakening and a pre-awakening increase in hemodynamic activation in the right prefrontal cortex, suggesting the structure's contribution to time estimation ability..
37. Makiko Watanabe, Akiko Hida, Shingo Kitamura, Minori Enomoto, Yosuke Ohsawa, Yasuko Katayose, Kentaro Nozaki, Yoshiya Moriguchi, Sayaka Aritake, Shigekazu Higuchi, Miyuki Tamura, Mie Kato, Kazuo Mishima, Rhythmic expression of circadian clock genes in human leukocytes and beard hair follicle cells, Biochemical and Biophysical Research Communications, 10.1016/j.bbrc.2012.08.008, 425, 4, 902-907, 2012.09, Evaluating individual circadian rhythm traits is crucial for understanding the human biological clock system. The present study reports characterization of physiological and molecular parameters in 13 healthy male subjects under a constant routine condition, where interfering factors were kept to minimum. We measured hormonal secretion levels and examined temporal expression profiles of circadian clock genes in peripheral leukocytes and beard hair follicle cells. All 13 subjects had prominent daily rhythms in melatonin and cortisol secretion. Significant circadian rhythmicity was found for PER1 in 9 subjects, PER2 in 3 subjects, PER3 in all 13 subjects, and BMAL1 in 8 subjects in leukocytes. Additionally, significant circadian rhythmicity was found for PER1 in 5 of 8 subjects tested, PER2 in 2 subjects, PER3 in 6 subjects, and BMAL1 in 3 subjects in beard hair follicle cells. The phase of PER1 and PER3 rhythms in leukocytes correlated significantly with that of physiological rhythms. Our results demonstrate that leukocytes and beard hair follicle cells possess an endogenous circadian clock and suggest that PER1 and PER3 expression would be appropriate biomarkers and hair follicle cells could be a useful tissue source for the evaluation of biological clock traits in individuals..
38. Miyuki Tamura, Yoshiya Moriguchi, Shigekazu Higuchi, Akiko Hida, Minori Enomoto, Jun Umezawa, Kazuo Mishima, Neural network development in late adolescents during observation of risk-taking action, PLoS One, 10.1371/journal.pone.0039527, 7, 6, 2012.06, Emotional maturity and social awareness are important for adolescents, particularly college students beginning to face the challenges and risks of the adult world. However, there has been relatively little research into personality maturation and psychological development during late adolescence and the neural changes underlying this development. We investigated the correlation between psychological properties (neuroticism, extraversion, anxiety, and depression) and age among late adolescents (n = 25, from 18 years and 1 month to 22 years and 8 months). The results revealed that late adolescents became less neurotic, less anxious, less depressive and more extraverted as they aged. Participants then observed video clips depicting hand movements with and without a risk of harm (risk-taking or safe actions) during functional magnetic resonance imaging (fMRI). The results revealed that risk-taking actions elicited significantly stronger activation in the bilateral inferior parietal lobule, temporal visual regions (superior/middle temporal areas), and parieto-occipital visual areas (cuneus, middle occipital gyri, precuneus). We found positive correlations of age and extraversion with neural activation in the insula, middle temporal gyrus, lingual gyrus, and precuneus. We also found a negative correlation of age and anxiety with activation in the angular gyrus, precentral gyrus, and red nucleus/substantia nigra. Moreover, we found that insula activation mediated the relationship between age and extraversion. Overall, our results indicate that late adolescents become less anxious and more extraverted with age, a process involving functional neural changes in brain networks related to social cognition and emotional processing. The possible neural mechanisms of psychological and social maturation during late adolescence are discussed..
39. Yumi Fukuda, Shigekazu Higuchi, Akira Yasukouchi, Takeshi Morita, Distinct responses of cones and melanopsin-expressing retinal ganglion cells in the human electroretinogram., Journal of Physiological Anthropology, 10.1186/1880-6805-31-20, 31, 2012.01, The discovery of the novel photoreceptor, melanopsin-expressing retinal ganglion cells (mRGCs), has raised researchers' interest in photoreceptive tasks performed by the mRGC, especially in non-image-forming visual functions. In a prior study, we investigated the mRGC response to light stimuli independent of rods and cones with the four-primary illumination system, which modulates stimulus levels to the mRGC and cones independently, and mRGC baseline responses were recorded in the electroretinogram (ERG). In the present study, we used the same illumination system to compare independent responses of the mRGC and cones in five subjects (mean ± SD age, 23.0 ± 1.7 years). The ERG waveforms were examined as direct measurements of responses of the mRGCs and cones to stimulation (250 msec). Implicit times (the time taken to peaks) and peak values from 30 stimuli given to each subject were analyzed. Two distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response. The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08). Implicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC's sluggish responses. This is the first report of amplitudes and implicit time in the ERG from the response of the mRGC that is independent of rods and cones, and obtained using the four-primary illumination system..
40. , [URL].
41. Shigekazu Higuchi, Tomomi Fukuda, Tomoaki Kozaki, Masaya Takahashi, Nobuhiko Miura, Effectiveness of a red-visor cap for preventing light-induced melatonin suppression during simulated night work, Journal of Physiological Anthropology, 10.2114/jpa2.30.251, 30, 6, 251-258, 2011, Bright light at night improves the alertness of night workers. Melatonin suppression induced by light at night is, however, reported to be a possible risk factor for breast cancer. Short-wavelength light has a strong impact on melatonin suppression. A red-visor cap can cut the short-wavelength light from the upper visual field selectively with no adverse effects on visibility. The purpose of this study was to investigate the effects of a red-visor cap on light-induced melatonin suppression, performance, and sleepiness at night. Eleven healthy young male adults (mean age: 21.2±0.9yr) volunteered to participate in this study. On the first day, the subjects spent time in dim light (<15 lx) from 20:00 to 03:00 to measure baseline data of nocturnal salivary melatonin concentration. On the second day, the subjects were exposed to light for four hours from 23:00 to 03:00 with a nonvisor cap (500 lx), red-visor cap (approx. 160 lx) and blue-visor cap (approx. 160 lx). Subjective sleepiness and performance of a psychomotor vigilance task (PVT) were also measured on the second day. Compared to salivary melatonin concentration under dim light, the decrease in melatonin concentration was significant in a nonvisor cap condition but was not significant in a red-visor cap condition. The percentages of melatonin suppression in the nonvisor cap and red-visor cap conditions at 4hours after exposure to light were 52.6±22.4% and 7.7±3.3%, respectively. The red-visor cap had no adverse effect on performance of the PVT, brightness and visual comfort, though it tended to increase subjective sleepiness. These results suggest that a red-visor cap is effective in preventing melatonin suppression with no adverse effects on vigilance performance, brightness and visibility..
42. Sayaka Aritake-Okada, Shigekazu Higuchi, Hiroyuki Suzuki, Kenichi Kuriyama, Minori Enomoto, Takahiro Soshi, Shingo Kitamura, Makiko Watanabe, Akiko Hida, Masato Matsuura, Makoto Uchiyama, Kazuo Mishima, Diurnal fluctuations in subjective sleep time in humans, Neuroscience Research, 10.1016/j.neures.2010.07.2040, 68, 3, 225-231, 2010.11, Humans have the ability to estimate the passage of time in the absence of external time cues. In this study, we subjected 22 healthy males (aged 21.8 ± 1.9 years) to a 40-min nap trial followed by 80 min of wakefulness repeated over 28 h, and investigated the relationship between various sleep parameters and the discrepancy (ΔST) of time estimation ability (TEA) during sleep, defined by the difference between actual sleep time (ST) and subjective sleep time (sub-ST) in each nap interval. Both ST and sub-ST were significant diurnal fluctuations with the peak in the early morning (9 h after dim-light melatonin onset time, 2 h after nadir time of core body temperature rhythm), and subjective sleep duration was estimated to be longer than actual times in all nap intervals (sub-ST > ST). There were significant diurnal fluctuations in discrepancy (sub-ST-ST) of TEA during sleep, and the degree of discrepancy correlated positively with increase in the amount of REM sleep and decrease in the amount of slow-wave sleep. These findings suggest that human TEA operates at a certain level of discrepancy during sleep, and that this discrepancy might be related to the biological clock and its associated sleep architecture..
43. Yumi Fukuda, Sei ichi Tsujimura, Shigekazu Higuchi, Akira Yasukouchi, Takeshi Morita, The ERG responses to light stimuli of melanopsin-expressing retinal ganglion cells that are independent of rods and cones, Neuroscience Letters, 10.1016/j.neulet.2010.05.080, 479, 3, 282-286, 2010.08, The mechanisms by which melanopsin-expressing retinal ganglion cells (mRGCs) regulate circadian rhythms in humans have not been established. To understand mRGC characteristics and their role independent of effects due to the rods and cones, mRGC responses should be induced or measured independent of cone and rod responses. In the present study, we obtained results from light stimuli which differentially induce only the mRGC response by using a receptor-silent substitution technique. The mRGCs responded linearly to contrast changes of light stimuli, whereas they showed complicated responses to frequency changes with regard to the latency of response time. These results suggest that mRGC behavior is not a simple response to the various frequencies found in solar light but may be related to intrinsic neural circuits with feedback connections in the mRGC pathway. The results in this study also demonstrated that the test stimuli affected only the mRGC response and that this could be successfully detected by using the electroretinogram (ERG)..
44. Minori Enomoto, Takako Tsutsui, Sadanori Higashino, Masaaki Otaga, Shigekazu Higuchi, Sayaka Aritake, Akiko Hida, Miyuki Tamura, Masato Matsuura, Yoshitaka Kaneita, Kiyohisa Takahashi, Kazuo Mishima, Sleep-related problems and use of hypnotics in inpatients of acute hospital wards, General Hospital Psychiatry, 10.1016/j.genhosppsych.2010.01.015, 32, 3, 276-283, 2010.05, Objective: Although sleep disorders are highly prevalent among patients with physical disorders, only limited information is available about the actual status of sleep-related problems in inpatients of acute hospital wards. We conducted a multicenter cross-sectional observational survey investigating the prevalence of sleep disorders and use of hypnotic-sedative drugs among inpatients of acute wards in 44 general hospitals in Japan. Method: Questionnaire-, actigraph- and observation-based sleep evaluations were simultaneously performed in 557 adult inpatients [mean age 72.8±12.8 (S.D.) years] of acute wards during a one-month period in July 2007. Results: Of the 421 patients with data available, 22.3% had at least one of the following sleep disorders: sleep apnea syndrome, restless legs syndrome, periodic limb movement disorder and nocturnal behavior disorder. Similarly, 62.7% had insomnia, 6.9% had severe daytime sleepiness and 12.8% had other sleep-related symptoms. Only 13.8% were free of any sleep-related problem. Although 33.7% of insomnia patients were taking hypnotic-sedative drugs, 65.2% of them complained of residual insomnia symptoms. Conclusion: The findings obtained in this study have revealed the remarkably high prevalence of sleep-related problems experienced by inpatients of acute hospital wards in Japan. Proper diagnosis of sleep disorders should be made among patients with physical disorders..
45. Keita Ishibashi, Satoshi Arikura, Tomoaki Kozaki, Shigekazu Higuchi, Akira Yasukouchi, Thermoregulatory effect in humans of suppressed endogenous melatonin by pre-sleep bright-light exposure in a cold environment, Chronobiology International, 10.3109/07420521003794069, 27, 4, 782-806, 2010.05, This study investigated the physiological function of suppressed melatonin through thermoregulation in a cold environment. Interactions between thermoregulation directly affected by exposure to a cold environment and indirectly affected by endogenous melatonin suppression by bright-light exposure were examined. Ten male subjects were exposed to two different illumination intensities (30 and 5000 lux) for 4.5h, and two different ambient temperatures (15 and 27°C) for 2h before sleep under dark and thermoneutral conditions. Salivary melatonin level was suppressed by bright light (p<0.001), although the ambient temperature condition had no significant effect on melatonin. During sleep, significant effects of pre-sleep exposure to a cold ambient temperature (p<0.001) and bright light (p<0.01) on rectal temperature (Tre) were observed. Pre-sleep, bright-light exposure led to an attenuated fall in Tre during sleep. Moreover, Tre dropped more precipitously after cold exposure than thermoneutral conditions (cold: -0.54±0.07°Ch; thermoneutral: -0.16±0.03°Ch; p<0.001). Pre-sleep, bright-light exposure delayed the nadir time of Tre under thermoneutral conditions (p<0.05), while cold exposure masked the circadian rhythm with a precipitous decrease in T re. A significant correlation between the Tre nadir and melatonin level (r-0.774, p<0.05) indicated that inter-individual differences with higher melatonin levels lead to a reduction in Tre after cold exposure. These results suggest that suppressed endogenous melatonin inhibits the downregulation of the body temperature set-point during sleep..
46. Sayaka Aritake-Okada, Makoto Uchiyama, Hiroyuki Suzuki, Hirokuni Tagaya, Kenichi Kuriyama, Masato Matsuura, Kiyohisa Takahashi, Shigekazu Higuchi, Kazuo Mishima, Time estimation during sleep relates to the amount of slow wave sleep in humans, Neuroscience Research, 10.1016/j.neures.2008.11.001, 63, 2, 115-121, 2009.02, Humans have the ability to estimate the amount of time that has elapsed during sleep (time estimation ability; TEA) that enables a subset of individuals to wake up at a predetermined time without referring to a watch or alarm clock. Although previous studies have indicated sleep structure as a key factor that might influence TEA during sleep, which sleep parameters could affect the TEA has not been clarified. We carried out an experimental study in which 20 healthy volunteers participated in six time estimation trials during the 9-h nighttime sleep (NS) experiment or daytime sleep (DS) experiment. The time estimation ratio (TER, ratio of the subjective estimated time interval to actual time interval) decreased significantly from the first to the sixth trial in both the NS and DS experiments. TER correlated positively with slow wave sleep (SWS) in both experiments, suggesting that SWS was a determining factor in accurate time estimation, irrespective of circadian phase they slept. No other sleep parameters showed steady influence on TEA. The present findings demonstrate that longer period of SWS is associated with the longer sleep time they subjectively experienced during sleep..
47. Minori Enomoto, Takuro Endo, Kazue Suenaga, Naoki Miura, Yasushi Nakano, Sayaka Kohtoh, Yujiro Taguchi, Sayaka Aritake, Shigekazu Higuchi, Masato Matsuura, Kiyohisa Takahashi, Kazuo Mishima, Newly developed waist actigraphy and its sleep/wake scoring algorithm, Sleep and Biological Rhythms, 10.1111/j.1479-8425.2008.00377.x, 7, 1, 17-22, 2009.02, The purpose of this study was to formulate an algorithm for assessing sleep/waking from activity intensities measured with a waist-worn actigraphy, the Lifecorder PLUS (LC; Suzuken Co. Ltd., Nagoya, Japan), and to test the validity of the algorithm. The study consisted of 31 healthy subjects (M/F = 20/11, mean age 31.7years) who underwent one night of simultaneous measurement of activity intensity by LC and polysomnography (PSG). A sleep(S)/wake(W) scoring algorithm based on a linear model was determined through discriminant analysis of activity intensities measured by LC over a total of 235h and 56min and the corresponding PSG-based S/W data. The formulated S/W scoring algorithm was then used to score S/W during the monitoring epochs (2min each, 7078 epochs in total) for each subject. The mean agreement rate with the corresponding PSG-based S/W data was 86.9%, with a mean sensitivity (sleep detection) of 89.4% and mean specificity (wakefulness detection) of 58.2%. The agreement rates for the individual stages of sleep were 60.6% for Stage 1, 89.3% for Stage 2, 99.2% for Stage 3 + 4, and 90.1% for Stage REM. These results demonstrate that sleep/wake activity in young to middle-aged healthy subjects can be assessed with a reliability comparable to that of conventional actigraphy through LC waist actigraphy and the optimal S/W scoring algorithm..
48. Akiko Hida, Hiroaki Kusanagi, Kohtoku Satoh, Tomonori Kato, Yasuhiro Matsumoto, Masaru Echizenya, Tetsuo Shimizu, Shigekazu Higuchi, Kazuo Mishima, Expression profiles of PERIOD1, 2, and 3 in peripheral blood mononuclear cells from older subjects, Life Sciences, 10.1016/j.lfs.2008.10.012, 84, 1-2, 33-37, 2009.01, Aims: Circadian clocks regulate daily rhythms of behavior and physiology such as the sleep-wake cycle and hormonal secretion. Numerous characteristics of the behavioral and physiological processes change with age. In this study, we evaluated the circadian clockwork in older people by measuring daily profiles of PERIOD (PER) gene expression in peripheral blood mononuclear cells (PBMCs). Main methods: Blood samples were collected from 6 healthy older subjects (mean age 62 years) at 2-h intervals over a 24-h period under a semi-constant routine condition where masking effects are minimized. PBMCs were isolated from whole blood and temporal mRNA expression profiles of PER1, PER2, and PER3 were determined by RT-PCR. Phases of the PER rhythms, and times of sleep onset and offset were determined using data from those subjects who showed significant 24-h rhythms. The values for the parameters were compared between the older subjects and 8 young control subjects (mean age 21 years). Key findings: Prominent daily rhythms of PER1, PER2, and PER3 mRNA levels, advanced sleep-wake timing and advanced phases of PER rhythms were observed in the older subjects compared to the young controls. There was no significant age-related phase difference in PER1 or PER2 rhythm with respect to sleep timing; however, PER3 expression pattern was altered in the older subjects. Significance: This preliminary study shows that human circadian clockwork in PBMCs remains intact at least until the presenile stage and suggests that the altered PER3 expression pattern may reflect decreased homeostatic sleep drive in older people..
49. Shigekazu Higuchi, Keita Ishibashi, Sayaka Aritake, Minori Enomoto, Akiko Hida, Miyuki Tamura, Tomoaki Kozaki, Yutaka Motohashi, Kazuo Mishima, Inter-individual difference in pupil size correlates to suppression of melatonin by exposure to light, Neuroscience Letters, 10.1016/j.neulet.2008.05.037, 440, 1, 23-26, 2008.07, There are large inter-individual differences in pupil size and suppression of melatonin by exposure to light. It has been reported that melatonin suppression by exposure to light increases when pupils are pharmacologically dilated. However, the correlation between normal inter-individual difference in pupil size and melatonin suppression by exposure to light is not clear. Twenty-three healthy male subjects (22.6 ± 2.7 years old) were exposed to light (1000 lx) for 2 h at night. The starting time of exposure to light was set to the ascending phase of melatonin concentration of each subject. Pupil area and saliva melatonin concentration were measured before exposure to light under dim light (15 lx) and during exposure to light. There were large inter-individual differences in melatonin suppression and pupil area. The mean and standard deviation of percentage of melatonin suppression 2 h after exposure to light was 57.2 ± 22.1%. The mean and standard deviation of pupil areas before and 2 h after exposure to light were 30.7 ± 7.9 mm2 and 15.9 ± 4.8 mm2, respectively. The percentage of melatonin suppression by light was positively correlated with pupil area during light exposure (r = 0.525, p < 0.02). Interestingly, it was also correlated with pupil area measured before exposure to light, under dim light (15 lx) (r = 0.658, p < 0.001). These results suggest that inter-individual difference in pupil area positively correlates with melatonin suppression by light and that pupil area under dim light is a predictor of inter-individual differences in melatonin suppression by light..
50. Masaya Takahashi, Kazuyuki Iwakiri, Midori Sotoyama, Shigekazu Higuchi, Masako Kiguchi, Mamoru Hirata, Naomi Hisanaga, Teruyo Kitahara, Kazushi Taoda, Katsuo Nishiyama, Work schedule differences in sleep problems of nursing home caregivers, Applied Ergonomics, 10.1016/j.apergo.2008.01.003, 39, 5, 597-604, 2008.01, Nursing home caregivers (n=775; 604 women; mean age 33.6 years) were studied to examine how work schedules affect their sleep. The shift group (n=536) worked under a rotating two-shift system (n=365), a rotating three-shift system (n=66), or other types of shifts (n=78). The non-shift group included 222 caregivers. Participants completed a questionnaire about working conditions, sleep problems, health, lifestyle, and demographic factors. The two-shift caregivers reported the highest levels of difficulty initiating sleep (DIS, 37.6%), insomnia symptoms (43.0%), and poor quality of sleep (24.9%) among the groups. Adjusted odds ratios for these problems were significantly greater for the two-shift caregivers than for non-shift counterparts: DIS (odds ratio 2.86, 95% confidence interval 1.57-5.20), insomnia symptoms (2.33, 1.36-4.02), and poor sleep quality (2.15, 1.09-4.22). Our data suggest that working under a rotating two-shift system, which has a longer night shift, is associated with an elevated risk of sleep problems for nursing home caregivers..
51. Shigekazu Higuchi, Yutaka Motohashi, Keita Ishibashi, Takafumi Maeda, Influence of eye colors of Caucasians and Asians on suppression of melatonin secretion by light, American Journal of Physiology - Heart and Circulatory Physiology, 10.1152/ajpregu.00355.2006, 292, 6, 2007.06, This experiment tested effects of human eye pigmentation depending on the ethnicity on suppression of nocturnal melatonin secretion by light. Ten healthy Caucasian males with blue, green, or light brown irises (light-eyed Caucasians) and 11 Asian males with dark brown irises (dark-eyed Asians) volunteered to participate in the study. The mean ages of the light-eyed Caucasians and dark-eyed Asians were 26.4 ± 3.2 and 25.3 ± 5.7 years, respectively. The subjects were exposed to light (1,000 lux) for 2 h at night. The starting time of exposure was set to 2 h before the time of peak salivary melatonin concentration of each subject, which was determined in a preliminary experiment. Salivary melatonin concentration and pupil size were measured before exposure to light and during exposure to light. The percentage of suppression of melatonin secretion by light was calculated. The percentage of suppression of melatonin secretion 2 h after the start of light exposure was significantly larger in light-eyed Caucasians (88.9 ± 4.2%) than in dark-eyed Asians (73.4 ± 20.0%) (P < 0.01). No significant difference was found between pupil sizes in light-eyed Caucasians and dark-eyed Asians. These results suggest that sensitivity of melatonin to light suppression is influenced by eye pigmentation and/or ethnicity..
52. Shigekazu Higuchi, Yutaka Motohashi, Keita Ishibashi, Takafumi Maeda, Less exposure to daily ambient light in winter increases sensitivity of melatonin to light suppression, Chronobiology International, 10.1080/07420520601139805, 24, 1, 31-43, 2007.01, This study was carried out to examine the seasonal difference in the magnitude of the suppression of melatonin secretion induced by exposure to light in the late evening. The study was carried out in Akita (39° North, 140° East), in the northern part of Japan, where the duration of sunshine in winter is the shortest. Ten healthy male university students (mean age: 21.9±1.2 yrs) volunteered to participate twice in the study in winter (from January to February) and summer (from June to July) 2004. According to Japanese meteorological data, the duration of sunshine in Akita in the winter (50.5 h/month) is approximately one-third of that in summer (159.7 h/month). Beginning one week prior to the start of the experiment, the level of daily ambient light to which each subject was exposed was recorded every minute using a small light sensor that was attached to the subject's wrist. In the first experiment, saliva samples were collected every hour over a period of 24 h in a dark experimental room (<15 lux) to determine peak salivary melatonin concentration. The second experiment was conducted after the first experiment to determine the percentage of melatonin suppression induced by exposure to light. The starting time of exposure to light was set 2 h before the time of peak salivary melatonin concentration detected in the first experiment. The subjects were exposed to light (1000 lux) for 2 h using white fluorescent lamps (4200 K). The percentage of suppression of melatonin by light was calculated on the basis of the melatonin concentration determined before the start of exposure to light. The percentage of suppression of melatonin 2 h after the start of exposure to light was significantly greater in winter (66.6±18.4%) than summer (37.2±33.2%), p<0.01). The integrated level of daily ambient light from rising time to bedtime in summer was approximately twice that in winter. The results suggest that the increase in suppression of melatonin by light in winter is caused by less exposure to daily ambient light..
53. Takafumi Maeda, Tetsuhito Fukushima, Keita Ishibashi, Shigekazu Higuchi, Involvement of basal metabolic rate in determination of type of cold tolerance, Journal of Physiological Anthropology, 10.2114/jpa2.26.415, 26, 3, 415-418, 2007, This study aimed to assess the relationship between basal metabolic rate (BMR) and metabolic heat production, and to clarify the involvement of BMR in determining the phenotype of cold tolerance. Measurements of BMR, maximum oxygen uptake, and cold exposure test were conducted on ten males. In the cold exposure test, rectal (Trec) and mean skin temperatures (T ms), oxygen uptake, and blood flow at forearm (BFarm) were measured during exposure to cold (10°C) for 90min. Significant correlations were observed between BMR and increasing rate of oxygen uptake, as well as between decreasing rate of BFarm and increasing rate of oxygen uptake at the end of cold exposure. These findings suggested that individuals with a lower BMR were required to increase their metabolic heat production during cold exposure, and that those with a higher BMR were able to moderate increased metabolic heat production during cold exposure because they were able to reduce heat loss. This study showed that BMR is an important factor in determining the phenotype of cold tolerance, and that individuals with a low BMR showed calorigenic-type cold adaptation, whereas subjects with a high BMR exhibited adiabatic-type cold adaptation by peripheral vasoconstriction..
54. Shigekazu Higuchi, Yutaka Motohashi, Yang Liu, Akira Maeda, Effects of playing a computer game using a bright display on presleep physiological variables, sleep latency, slow wave sleep and REM sleep, Journal of Sleep Research, 10.1111/j.1365-2869.2005.00463.x, 14, 3, 267-273, 2005.09, Epidemiological studies have shown that playing a computer game at night delays bedtime and shortens sleeping hours, but the effects on sleep architecture and quality have remained unclear. In the present study, the effects of playing a computer game and using a bright display on nocturnal sleep were examined in a laboratory. Seven male adults (24.7 ± 5.6 years old) played exciting computer games with a bright display (game-BD) and a dark display (game-DD) and performed simple tasks with low mental load as a control condition in front of a BD (control-BD) and DD (control-DD) between 23:00 and 1:45 hours in randomized order and then went to bed at 2:00 hours and slept until 8:00 hours. Rectal temperature, electroencephalogram (EEG), heart rate and subjective sleepiness were recorded before sleep and a polysomnogram was recorded during sleep. Heart rate was significantly higher after playing games than after the control conditions, and it was also significantly higher after using the BD than after using the DD. Subjective sleepiness and relative theta power of EEG were significantly lower after playing games than after the control conditions. Sleep latency was significantly longer after playing games than after the control conditions. REM sleep was significantly shorter after the playing games than after the control conditions. No significant effects of either computer games or BD were found on slow-wave sleep. These results suggest that playing an exciting computer game affects sleep latency and REM sleep but that a bright display does not affect sleep variables..
55. Takafumi Maeda, Akiko Sugawara, Tetsuhito Fukushima, Shigekazu Higuchi, Keita Ishibashi, Effects of lifestyle, body composition, and physical fitness on cold tolerance in humans, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.24.439, 24, 4, 439-443, 2005.07, In the present study, we attempted to clarify the effects of lifestyle and body compositions on basal metabolism and to clarify the effects of physical training on thermoregulatory responses to cold. Basal metabolism, body compositions, and questionnaires regarding lifestyle were evaluated in 37 students. From multiple linear regression analysis, sex, muscle weight, fat intake, and diurnal temperature were selected as significant explanatory variables. In a second experiment, rectal and the skin temperature at 7 different points as well as the oxygen uptake of eight males were measured at 10°C for 90 min before and after training. The decline in rectal temperature that was observed before training was not observed after training. In addition, rectal temperature was significantly higher at post-training than at pre-training. These results suggest that some lifestyle factors affect cold tolerance; in particular, daily activity might improve our ability to control heat radiation and basal heat production..
56. Keita Ishibashi, Takafumi Maeda, Shigekazu Higuchi, Akira Yasukouchi, Error and individual difference in cardiovascular responses to orthostatic stress in humans, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.24.339, 24, 4, 339-343, 2005.07, Variations in cardiovascular responses to orthostatic stress were investigated in terms of physiological polymorphism. Variations of physiological measurements are subdivided into individual differences and measurement errors. However, individual differences are often considered to be an error in statistical analysis due to its limitations in experimental design. In order to discuss about the relative contribution of individual difference in cardiovascular responses to postural changes, percent contribution (PC) was estimated using the Taguchi method. Six healthy male adults (age range: 21-27) were subjected to orthostatic stress by inducing a postural inclination of 60° head-up-tilting to the horizontal, and the responses were measured thrice in each subject on different days. The respective changes of heart rate (HR) and stroke volume (SV) in the period from the resting supine to the head-up-tilt position were significantly increased (p<0.01) and decreased (p<0.01) without affecting the mean blood pressure (MBP). The PC of individual difference in HR showed a significantly higher ratio of individual difference during the head-up-tilt (71.4-76.2%) compared with supine rest (0.0-50.4%). While the main variations of HR during supine rest were not the individual differences between the subjects, the day-to-day differences within the subject were significant. The PC of individual differences in MBP and SV constantly displayed a significant difference between the subjects. These results suggest that the strategy for maintaining stable cardiovascular regulation may be different even in normal subjects. In the perspective of physiological parameters, PC monitoring may serve as an empirical approach to evaluate physiological polymorphism..
57. Shigekazu Higuchi, Yutaka Motohashi, Takafumi Maeda, Keita Ishibashi, Relationship between individual difference in melatonin suppression by light and habitual bedtime, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.24.419, 24, 4, 419-423, 2005.07, The purpose of this study was to determine the relationship between individual difference in melatonin suppression by exposure to light and habitual bedtime. Seventeen healthy male students (mean age: 22.6±2.4yr) volunteered to participate in the study. The subjects were exposed to light (1000 1x) for 2 hours from 2 hours before the time of peak salivary melatonin concentration. Two hours after exposure to the light, melatonin suppression had occurred in fifteen subjects. No significant correlation was found between the rate of melatonin suppression and habitual bedtime in the fifteen subjects in whom melatonin suppression occurred. However, the habitual bedtime of the two subjects in whom melatonin suppression did not occur was earlier than that of the other subjects. These results suggest that there are some people with very low sensitivity to light and that this may affect habitual bedtime..
58. Akira Maeda, Norihiro Shima, Hidetsugu Nishizono, Hiroshi Kurata, Shigekazu Higuchi, Yutaka Motohashi, Lower extremity function in terms of shock absorption when landing with unsynchronized feet, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.22.279, 22, 6, 279-283, 2003.11, The purpose of this study was to clarify the lower extremity function in terms of the shock absorption during unsynchronized-foot landings. The characteristics of the supination and pronation in the ankle joint at landing were investigated, assuming that the measurements of the impact force on the body could be demonstrated by the changes that occurred during 3 different landing motions: - unsynchronized-foot landings, synchronized-foot landings, and one-foot landings. Subjects jumped to the floor from 10-cm footstools 3 times for each type of landing. For the synchronized-foot landing, the rear foot angle was 92.2° at the start of landing and did not change significantly from landing start to 100 msec. For the one-foot landing, rear foot angle was 95.1° at the start of landing and decreased rapidly to 87.1° by 75 msec, and then increased rapidly to 90.8° by 140 msec. For the unsynchronized-foot landing, the rear foot angle was 93.8° at the start of the landing, decreased rapidly to 88.0° by 75 msec, and then increased rapidly to 89.9° by 115 msec. It was clarified that the lower extremity function for the shock attenuation during landing with the unsynchronized-foot was similar to that with one-foot landings, and the lower extremity function for supporting the body after another foot landing was similar to that after the synchronized-foot landings in this study..
59. Shigekazu Higuchi, Yutaka Motohashi, Yang Liu, Mio Ahara, Yoshihiro Kaneko, Effects of VDT tasks with a bright display at night on melatonin, core temperature, heart rate, and sleepiness, Journal of Applied Physiology, 10.1152/japplphysiol.00616.2002, 94, 5, 1773-1776, 2003.05, The effects of performing video display terminal (VDT) tasks with a bright display (BD) at night on nocturnal salivary melatonin concentration, rectal temperature, heart rate, and sleepiness were examined. Seven healthy male adults performed exciting VDT tasks with a BD and a dark display (DD) and boring VDT tasks with a BD and a DD from 2300 to 0200. The light intensities of the BD and DD were 45 and 15 lx at each subject's eye level, respectively. The exciting VDT task with both BD and DD significantly suppressed the nocturnal decrease in rectal temperature and heart rate and the nocturnal increase in sleepiness. The BD significantly suppressed the nocturnal decrease in rectal temperature during both exciting and boring VDT tasks. The nocturnal salivary melatonin concentration was significantly suppressed by the combination of the exciting task and BD. The results suggest that performing an exciting VDT task with a BD suppresses the nocturnal changes in melatonin concentration and other physiological indicators of human biological clocks..
60. Yutaka Motohashi, Shigekazu Higuchi, Mio Ahara, Yoshihiro Kaneko, Sleep time and working conditions of office workers, Sleep and Biological Rhythms, 10.1046/j.1446-9235.2003.00021.x, 1, 2, 131-132, 2003.03, The relationship between sleep time and working conditions was studied in office workers, from the aspect of health promotion. Data obtained from health checkups conducted on 1366 office workers, including life-style and working conditions, were analyzed. The subjects were divided into three groups: group 1 (less than 5 h of sleep per day), group 2 (5–8 h of sleep per day), and group 3 (more than 8 h of sleep per day). Blood biochemical variables showed no differences among the three groups. The percentage of subjects in group 1 who worked overtime was significantly higher than the percentages in groups 2 and 3. In conclusion, the amount of sleep time is associated with the amount of work done by office workers..
61. Y. Liu, Shigekazu Higuchi, Y. Motohashi, Changes in postural sway during a period of sustained wakefulness in male adults, Occupational Medicine, 10.1093/occmed/51.8.490, 51, 8, 490-495, 2001.12, Nocturnal variations in postural sway during a period of sustained wakefulness were studied in seven healthy male adults. Postural sways with the subject's eyes open and with them closed were measured every hour from 22:00 to 04:00 h the following day. Parameters of postural sway [rectangle area (RA), root mean square of length in the anterior-posterior direction (RMSL-y), and medium-frequency-band (0.2-1.0 Hz) power of postural sway in the lateral (MF-x) and anterior-posterior (MF-y) directions] showed significant nocturnal variations. RA, RMSL-y, MF-x and MF-y increased after midnight and reached peaks at 04:00 h. Moreover, changes in RA and MF-y depended on visual conditions. The increases in RA and MF-y were larger with the eyes closed than with them open. These postural sway parameters showed positive correlations with subjectively rated sleepiness and negative correlations with electroencephalographic alpha activity. The results suggest that changes in postural sway during the night are influenced by the increase in sleepiness..
62. Akira Maeda, Kazutoshi Nakamura, Shigekazu Higuchi, Takao Yuasa, Yutaka Motohashi, Postural sway during cane use by patients with stroke, American Journal of Physical Medicine and Rehabilitation, 10.1097/00002060-200112000-00006, 80, 12, 903-908, 2001.12, Objective: To quantitatively evaluate the effects of body support with a cane on postural sway by measuring gravity-center sway of patients with stroke who reside at home. Design: The subjects were 41 patients with stroke and 36 healthy independent elderly people. Each subject stood in the standard Romberg position on a gravicorder under two conditions: without support and with a cane. Results: In both groups, the largest area of gravity-center sway occurred when the subjects stood without support. The area of gravity-center sway of the patients with stroke was significantly greater than that of the healthy independent elderly. In the patients with stroke group, the percentage decrease in the standing position with the cane was 58.0% in the men and 53.9% in the women, as opposed to 67.7% in the men and 67.8% in the women in the group of healthy independent elderly. Conclusion: The authors quantitatively evaluated the effects of body support with a cane on postural sway of patients with stroke. The effect of body support with cane on postural sway of patients with stroke was more effective than that of healthy independent elderly..
63. Shigekazu Higuchi, Yang Liu, Takao Yuasa, Akira Maeda, Yutaka Motohashi, Diurnal variations in alpha power density and subjective sleepiness while performing repeated vigilance tasks, Clinical Neurophysiology, 10.1016/S1388-2457(01)00527-2, 112, 6, 997-1000, 2001.06, Objective: Diurnal variations in EEG activity and subjectively rated sleepiness while performing repeated vigilance tasks were examined. Methods: Nine diurnally active healthy males underwent repeated vigilance tasks at 08:00, 11:00, 14:00, 17:00 and 20:00 h. An electroencephalogram (EEG) was taken while the subjects performed the tasks with their eyes open. The alpha power spectra (8.6-13.3 Hz) of EEG was integrated. Subjectively rated sleepiness, reaction time and oral temperature were also measured. Results: Significant diurnal variations were found for alpha power, subjectively rated sleepiness and oral temperature. The alpha power was significantly smaller at 08:00 than at 11:00, 14:00, 17:00 and 20:00 h. The subjectively rated sleepiness was significantly larger at 08:00 than at 11:00, 17:00 and 20:00 h. The diurnal variation in alpha power did not correspond to that in subjectively rated sleepiness. On the other hand, repeated vigilance tasks increased the alpha power, subjectively rated sleepiness and reaction time at each time of day. The increase in alpha power was significantly greater at 14:00 than at 08:00 and 20:00 h. Conclusions: The diurnal variation was found in alpha power while performing vigilance tasks. Furthermore, the increase in alpha power with repetition of the task depended on the time of day..
64. Takao Yuasa, Akira Maeda, Shigekazu Higuchi, Yutaka Motohashi, Quantitative EEG data and comprehensive ADL (Activities of Daily Living) evaluation of stroke survivors residing in the community, Journal of Physiological Anthropology, 10.2114/jpa.20.37, 20, 1, 37-41, 2001.01, The purpose of this study was to investigate the hypothesis that EEG values match other comprehensive activities of daily living (ADL) evaluations between stroke survivors and normal controls. Various functions related to ADL were examined by means of ADL assessments (Measurement of Competence in the Elderly Living at Home, Barthel Index, Stroke Impairment Assessment Set, time needed to walk 10 metres) and biosocial synchronization (the questionnaire on biosocial rhythms of daily living). EEG was undertaken using a computer-assisted portable EEG recorder. The power spectra were computed using a fast Fourier transformation analysis (FFT). The absolute and relative powers (percent of the total EEG power) of 5 frequency bands (delta, theta, alpha 1, alpha 2 and beta) and the peak frequency were analyzed. In comparing stroke survivors and the independent elderly, the latter had higher scores than the former in assessments of various functions related to ADL. The absolute and relative power of the delta band were lower in normal controls, and the relative power of the alpha (2) band and the peak frequency were higher than those of stroke survivors. Among the correlations between EEG and ADL assessments, the absolute and relative power of the alpha (2) band correlated significantly with ADL assessments of stroke survivors with right hemiplegia. The peak frequency was significantly increased in cases with high ADL scores. In conclusion, significant correlations were identified between the quantitative EEG data of stroke survivors in the chronic stage, living in the community, and ADL-related functions. Computer-assisted portable EEG recording is a potentially useful screening tool for objectively evaluating the functional levels of stroke survivors in field work..
65. Akira Maeda, Takao Yuasa, Kazutoshi Nakamura, Shigekazu Higuchi, Yutaka Motohashi, Physical performance tests after stroke
Reliability and validity, American Journal of Physical Medicine and Rehabilitation, 10.1097/00002060-200011000-00008, 79, 6, 519-525, 2000.11, Objective: To evaluate the reliability and validity of the modified physical performance tests for stroke survivors who live in a community. Design: The subjects included 40 stroke survivors and 40 apparently healthy independent elderly persons. The physical performance tests for the stroke survivors comprised two physical capacity evaluation tasks that represented physical abilities necessary to perform the main activities of daily living, e.g., standing-up ability (time needed to stand up from bed rest) and walking ability (time needed to walk 10 m). Results: Regarding the reliability of tests, significant correlations were confirmed between test and retest of physical performance tests with both short and long intervals in individuals after stroke. Regarding the validity of tests, the authors studied the significant correlations between the maximum isometric strength of the quardriceps muscle and the time needed to walk 10 m, centimeters reached while sitting and reaching, and the time needed to stand up from bed rest. Conclusions: The authors confirmed that there were significant correlations between the instrumental activity of daily living and the time needed to stand up from bed rest, along with the time needed to walk 10 m for the stroke survivors. These physical performance tests are useful guides for evaluating a level of activity of daily living and physical frailty of stroke survivors living in a community..
66. Shigekazu Higuchi, Yang Liu, Takao Yuasa, Akira Maeda, Yutaka Motohashi, Diurnal variation in the P300 component of human cognitive event-related potential, Chronobiology International, 10.1081/CBI-100101073, 17, 5, 669-678, 2000.09, Diurnal variation in the P300 component of the human cognitive event-related potential (ERP) was examined. The P300 component is considered to be a measure of neuroelectric activity related to cognitive functions such as attention allocation and information processing. Nine diurnally active healthy male subjects whose sleep-wake rhythms were synchronized prior to the experiment were studied. The P300 components oral temperature, heart rate, left- and right-hand grip strength, reaction time, subjectively rated sleepiness, attention level, and fatigue were measured at 08:00, 11:00, 14:00, 17:00, and 20:00. Significant diurnal variations in P300 latency, P300 amplitude, oral temperature, heart rate, left- and right-hand grip strength, subjectively rated sleepiness, and attention level were observed. The P300 latency at 08:00 was significantly longer than at 11:00, 17:00, and 20:00, while the P300 amplitude at 08:00 was significantly greater than at 17:00 and 20:00. The P300 latency was correlated positively with subjectively rated sleepiness and negatively correlated with subjectively rated attention level. These results suggest the existence of diurnal variation in human cognitive functions..
67. Y. Motohashi, A. Maeda, H. Wakamatsu, Shigekazu Higuchi, T. Yuasa, Circadian rhythm abnormalities of wrist activity of institutionalized dependent elderly persons with dementia, Journals of Gerontology - Series A Biological Sciences and Medical Sciences, 10.1093/gerona/55.12.M740, 55, 12, 2000.01, Background. The study objective was to clarify the descriptive characteristics of circadian rhythm abnormalities of wrist activity of the institutionalized elderly with dementia. Methods. We studied 82 elderly persons with dementia who were institutionalized in a long-term medical care facility. The ambulatory continuous monitoring of their wrist activity was conducted for 7 days at 1-minute intervals. The time series data were analyzed using the double-plotted chronogram, spectral analysis was performed using the fast Fourier transformation and periodogram analysis was performed as well. Results. The frequency of circadian rhythm abnormalities of wrist activity rhythm in elderly persons with dementia was 57.3% (47 out of 82). The abnormalities were classified into four categories: Severely impaired circadian rhythm type with no boundary between day and night, free-running rhythm type, decreased circadian amplitude type, and accentuation of ultradian rhythm type. Conclusion. This four-category classification system provides a scientific approach for studying the mechanisms of circadian activity rhythm abnormalities of elderly persons with dementia..
68. Yutaka Motohashi, Akira Maeda, Takao Yuasa, Shigekazu Higuchi, Reliability and validity of the questionnaire to determine the biosocial rhythms of daily living in the disabled elderly, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.19.263, 19, 6, 263-269, 2000.01, The questionnaire to determine the biosocial rhythms of daily living in the disabled elderly was newly developed. This questionnaire was aimed to evaluate a state of synchronization of biological rhythms in the disabled elderly. Eighteen items of the questionnaire relating to the synchronization of biological rhythms were finally selected by the test-retest method that was conducted for 68 disabled elderly living in a community with a duration of one year. The factor analysis showed that the questionnaire consisted of five factors: outdoor activities, ultradian rhythms, subjective evaluation of health status, social support, and sleep habits. The cumulative contribution rate of five factors was 53.2%. Reliability of the questionnaire was confirmed by a calculation of the Equal-length Spearman-Brown coefficients ranging from 0.60 to 0.80. Regarding the construct validity of the questionnaire, results of factor analysis showed five factors that were consistent with the synchronizers known in chronobiology. The total score of the questionnaire was significantly correlated to Barthel Index score and the competence score, suggesting that it partly reflects the activities of daily living of the disabled elderly. We conclude that a new questionnaire to determine the biosocial rhythm of daily living in the disabled elderly is useful to evaluate the biosocial synchronization of the disabled elderly because of its high reliability and validity..
69. Yang Liu, Shigekazu Higuchi, Yutaka Motohashi, Time-of-day effects of ethanol consumption on EEG topography and cognitive event-related potential in adult males, Journal of Physiological Anthropology and Applied Human Science, 10.2114/jpa.19.249, 19, 6, 249-254, 2000.01, Time-of-day effects of ethanol consumption on EEG topography and cognitive event-related potential in adult males were studied. Ethanol (0.5 g/kg) or control drink was orally administered to nine healthy males at 10:00 and 18:00. The alpha2 amplitude was significantly lower than that of the control at 0.5, 2.5 and 4.5 hours after ethanol consumption in the morning. These effects were observed in the left hemisphere and were only found after consumption in the morning. The subjectively rated attention was significantly lower than that of the control at 0.5 and 2.5 hours after ethanol consumption in the morning and at 0.5 hours after ethanol consumption in the evening. In contrast, the search speed of serial search task and P300 amplitude was significantly lower than that of the control at 2.5 hours after ethanol consumption in the evening. These results demonstrate that effects of ethanol are dependent on time-of-day of consumption. Ethanol consumption significantly lowered the alpha2 amplitude when consumed in the morning, and lowered P300 amplitude when consumed in the evening..
70. Yutaka Motohashi, Akira Maeda, Kazutoshi Nakamura, Shigekazu Higuchi, Yang Liu, Takao Yuasa, Sleep-wake rhythm and physical fitness in relation to activities of daily living in stroke survivors residing at home, Environmental Health and Preventive Medicine, 10.1007/BF02932262, 3, 4, 218-222, 1999.01, To clarify the relationship between sleep-wake rhythm, physical fitness, and competence level of elderly stroke survivors living at home, thirty- seven stroke survivors living at home (65.4 ± 7.3 years) voluntarily participated in a cross-sectional study with an interview survey and measurement of physical fitness. All subjects lived in a community and received community home health care services. Sleep-wake rhythm and competence were evaluated by the questionnaire method. Physical fitness in relation to daily living activities was measured by both the time needed to walk 10 meters and that needed to stand up from bed rest position. There was a significant positive correlation between rising time and the 10 meter walking time. Regarding rising time and the competence score, there was a significant negative correlation. Stroke survivors who actively participated in community activities arose earlier than those who had a negative attitude toward participation in community activities. The sleep-wake rhythm, especially rising time, and the participation in community activities were related to the high competence level of stroke survivors living at home. Strengthening the synchronization of the sleep-wake rhythm and increasing the social network may serve as useful procedures to improve the competence of stroke survivors living at home..
71. Y. Motohashi, Shigekazu Higuchi, A. Maeda, Y. Liu, T. Yuasa, K. Motohashi, K. Nakamura, Alteration of circadian time structure of blood pressure caused by night shift schedule, Occupational Medicine, 10.1093/occmed/48.8.523, 48, 8, 523-528, 1998.11, The effects of night shift schedules on circadian time structure of blood pressure were studied in seven healthy young subjects by continuous monitoring of blood pressure every 30 min for 72 h. In the control experiment, subjects were instructed to sleep at regular times with the light off at 00.00 h and the light on at 07.00 h. In the shift experiment, they were instructed to go to bed at 06.00 h and wake up at 11.00 h. The circadian rhythm of blood pressure rapidly phase delayed by 3.5 h in the second night shift day as a group phenomenon. individual differences in changes in power spectral patterns of blood pressure were found in the night shift schedule. Ultradian rhythmicity of blood pressure was more pronounced in three subjects, whereas the circadian rhythmicity was maintained in four subjects. These findings held when the adaptation to shift work was taken into account..
72. Akira Maeda, Kazutoshi Nakamura, Akihiko Otomo, Shigekazu Higuchi, Yutaka Motohashi, Body support effect on standing balance in the visually impaired elderly, Archives of Physical Medicine and Rehabilitation, 10.1016/S0003-9993(98)90100-9, 79, 8, 994-997, 1998.08, Objective: To evaluate the effectiveness of body support in compensating for decreased standing balance stability in elderly persons with visual impairment. Design: Standing balance was measured in a cross-section of elderly persons from two nursing homes-one for aged individuals with visual impairment, the other for aged individuals without visual impairment. Participants: The subjects were 44 visually impaired persons with a mean age of 79.0yrs and 39 people without visual impairment, mean age 76.3yrs. Outcome Measures: The area of gravity-center sway was measured with subjects standing on a gravicorder for 30sec in three positions: (1) without support, (2) with cane, (3) with light support by touching a wall. Results: Both men and women in the visually impaired group Swayed more than their sighted counterparts when standing without support, the only statistically significant difference between the two groups. For all subjects, the greatest degree of sway occurred when subjects stood unsupported, and the least sway occurred when subjects touched a wall for support. Conclusion: In visually impaired elderly persons, touching a wall for body support while standing is more effective than using a cane..
73. Y. Motohashi, Shigekazu Higuchi, A. Maeda, Men's time, women's time--sex differences in biological time structure., Applied human science : journal of physiological anthropology, 10.2114/jpa.17.157, 17, 4, 157-159, 1998.07.
74. T. Yuasa, Shigekazu Higuchi, A. Maeda, Y. Motohashi, Usefulness of computer-assisted portable EEG recorder for field work in applied human science., Applied human science : journal of physiological anthropology, 10.2114/jpa.17.149, 17, 4, 149-150, 1998.07.
75. Shigekazu Higuchi, Shigeki Watanuki, Akira Yasukouchi, M. Sato, Effects of changes in arousal level by continuous light stimulus on contingent negative variation (CNV)., Applied human science : journal of physiological anthropology, 10.2114/jpa.16.55, 16, 2, 55-60, 1997.03, The purpose of the present study was to investigate an inverted-U relationship between contingent negative variation (CNV) and arousal level which was influenced by extraneous environment. As an extraneous stimulant, stimulation by light was adopted, and five levels of luminance conditions, 10 cd/m2, 100 cd/m2, 320 cd/ m2, 1,000 cd/m2, and 1,800 cd/m2 were provided randomly. Under five luminance conditions, seven subjects who had been accustomed a measurement of CNV executed simple reaction time tasks to evoke CNV. Outside CNV, spontaneous EEG prior to S1 was measured as an indicator for arousal level. As a result, a negative correlation existed between the logarithm of luminance and the relative power value of alpha waves at Fz. Otherwise, an increase in luminance caused an increase in CNV amplitude until the luminance level reached 320 cd/m2, beyond which however CNV amplitude was found to decrease. These tendencies were most remarkable in the phase of early CNV at Fz. The low amplitude of early CNV seen in the high luminance conditions was inferred to have been induced by excessive arousal state because of the low relative power value of alpha waves, while the low amplitude in the low luminance conditions was inferred to have been induced by low arousal state because of the high relative power value of alpha waves. However, changes in arousal level by light stimulus caused no effect on reaction time. From these findings, it was suggested that a definite "inverted-U" relationship existed between the change in arousal level by light stimulation and resultant CNV, and that it could be discriminated as to whether reduction in CNV is caused by excessive arousal effect of environment by analyzing spontaneous EEG preceding S1..
76. Shigekazu Higuchi, Shigeki Watanuki, Akira Yasukouchi, Effects of reduction in arousal level caused by long-lasting task on CNV., Applied human science : journal of physiological anthropology, 10.2114/jpa.16.29, 16, 1, 29-34, 1997.01, The present study aimed at investigating an inverted-U relationship between contingent negative variation (CNV) and arousal level by examining the effects on CNV of gradually reduced arousal level by long-lasting task. The subjects conducted a simple reaction time task consisting of warning stimuli (S1) and imperative stimuli (S2). This task consisted of 200 trials and lasted about 40 minutes. During this task, spontaneous EEG before S1 and SPL (skin potential level) were measured as indicators for arousal level. The 200 CNV, EEG and SPL data were classified into 5 blocks each of which included 40 trials of data. Analysis was made in seven subjects in whom reduction in the arousal level in long-lasting task was shown by increase in the relative power values of alpha waves before S1 and decrease in the SPL. As a result, the amplitude of early CNV at Fz was observed to increase from the earlier half phase (block 1) to the middle phase (block 3) and to decrease from the middle phase (block 3) to the latter half (block 5). In the middle phase, the amplitude was the greatest. The low amplitude of early CNV in the early half of the task (block 1) was inferred to have been induced by excessive arousal state because of the low relative power values of alpha waves and the high SPL at this time. On the other hand, the low amplitude in the later phase (block 5) was inferred to have been induced by reduction in arousal level because of the high relative power values of alpha waves and the low SPL. These results suggested that CNV amplitude and arousal level was in an inverted-U relationship..