Munehisa Tamaki

Effects of a daytime nap in the aged.

This study evaluated the effects of the daytime nap on performance, mood and physiological measures in aged individuals. Participants were six healthy aged persons (M = 72.2 years old) who habitually napped in the afternoon three or more times a week. They participated under two conditions with an interval of 1 week. In the nap condition, the subjects went to bed at 13:00 h and slept for 30 min. In the rest condition, they just watched television. In both conditions, electroencephalogram (EEG), blood pressure, mood and performance were measured before and after a nap or rest. The daytime nap improved performance, decreased subjective sleepiness and fatigue, and attenuated EEG alpha band activity. Moreover, following a nap diastolic blood pressure significantly decreased. These findings suggest that a habitual daytime nap helps aged individuals to maintain their daytime physiological, psychological and behavioral arousal at an adequate level.

Influence of arousal level for functional magnetic resonance imaging (fMRI) study: simultaneous recording of fMRI and electroencephalogram.

Abstract Simultaneous recording of functional MRI (fMRI) and electroencephalogram (EEG) has been applied to several clinical fields, making it possible to monitor the arousal level of the subject during a cognitive task. The study confirmed that activated cerebral areas were different between high and low arousal levels during the smooth‐pursuit eye movement task. When arousal level was high, activations in the parietal eye field, frontal eye field (FEF), supplementary eye field (SMA), visual fields (V1) and occipito–temporal junction (V5) were found. In contrast, when arousal level was low, activations were found only in V1 and FEF. The results indicate that the monitoring of the arousal level of subjects using fMRI and EEG recordings simultaneously is crucial for detecting cortical activations during a cognitive task.

Effects of daytime activity on nocturnal sleep in the elderly.

This study investigates the relationship between the level of daytime activities and nocturnal sleep in the elderly using the wrist actigraph and ambulatory polysomnograph system. Five male and five female subjects (mean age = 73.8 ± 3.05 years; range 69–77 years) participated in this study. The level of daytime activity was positively correlated with the sleep efficiency of the subsequent night only for male subjects, who were shown to be less active during the daytime. The results imply that increments in the time spent on physical activities may improve the quality of nocturnal sleep in elderly male subjects.

Effects of volitional lifestyle on rest–activity cycle in the aged

The present study investigated the relationship among volitional lifestyle, activity and sleep in the aged. We selected 28 subjects over 65 years of age to survey volition to lifestyle. High‐volitional group (14 Ss, mean age: 74.1 years, seven males and seven females) and low‐volitional group (14 Ss, mean age: 73.0 years, seven males and seven females) were identified by the scale of self‐confidence and the Philadelphia Geriatric Center morale scale. Wrist activities were monitored by Actigraph for 10 or 14 consecutive days. The subjects recorded sleep logs by themselves for those days. It was found that high volitional aged individuals had a relatively well structured sleep in comparison with low volitional aged individuals, and that most of them took a clock dependent habitual nap around 14.00 h. On the other hand, low volitional aged individuals had a relatively poor structured sleep, and took a nap time‐dependently after 8 h from the morning rising time. These results suggest that high volitional aged individuals build a short nap into their well organized sleep‐life habits.

An Exploratory Study of Effects of Smoking on Mental Rotation and Mental Paper-Folding Task:

To demonstrate the positive effects of smoking on spatial-imagery processing, behavioral (hit ratio and reaction time) and physiological indices (EEGs and HR) were examined in 12 student volunteers. Subjects performed two spatial-imagery tasks, one mental rotation and the other mental paper-folding. The two tasks were performed before and after smoking and the results compared. Subjects participated in both control and smoking sessions. Reaction time decreased after smoking, while the hit ratio did not change. EEG contour maps derived from 12-channel records of the beta band showed activation of the frontal area during the spatial-imagery processing. After smoking, EEG laterality showed increased right-hemisphere dominance. These findings implied that smoking facilitated selective activation of the hemisphere and did not support Gilbert and Weslers hypothesis of left-hemisphere priming. Psychophysiological mechanisms of the effects of smoking were discussed.

Simultaneous recording of EEG and functional MRI

Abstract The simultaneous recording of the electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) provides a better understanding of the relationship between hemodynamic and electrical brain activation and is thought to be a powerful technique for studying brain function. However, the acquisition of EEG during fMRI experiments raises important practical issues for patient safety and for the artifacts of MRI images and EEG waveforms. It made it possible to acquire clear MRI images and EEG tracings with sufficient patient safety by using electrodes with register and with twisted leads. The simultaneous recording of fMRI and EEG has been applied to several clinical studies: epilepsy, sleep and ERP studies. It also makes it possible to monitor the arousal level of the subject during cognitive task. We confirmed that activated areas during pursuit eye movement tasks were different by the arousal level. Monitoring the arousal level of the subjects using fMRI and EEG simultaneous recording is thought to be crucial for the cognitive task.

Estimation of sleep quality using heart rate variability

Estimation of sleep quality using heart rate variability (HRV) with MEMcalc analysis was investigated. HF and LF/HF for HRV and actigram of the second night in twelve healthy young and ten healthy elderly persons were recorded. HF of the elderly people during whole night was lower than it of the youth. In the comparison in first half and latter half of the sleep, only the youth was significantly high the value in the latter half for LF/HF. In the next study, sleep initiating process for the subjects with difficult sleep initiation (DG, n = 8) and with non-difficult sleep initiation (NDG, n = 8) were polysomnographically recorded at second night controlled life-style, circadian rhythm and experimental condition. The HF in NDG increases from circadian-time 0 (customary bedtime), and LF/HF in NDG descends from lightoff-time immediately. However, there are no similar phenomena on sleep initiating process of DG. These results mentioned above suggest that sympathetic nervous activities fluctuate in accordance with sleep structure and process. HRV recording with actigram is available method to estimate the sleep quality in the field study.

Simultaneous recording by NIRS and VEP revealed the dominant response in left primary visual cortex

Introduction Visual evoked potential (VEP) is the response of electrical activity of neurons recorded during 0 (ETH) 300 msec after the stimulation. Functional MRI, PET and NIRS that were recently used for functional brain mapping record the hemodynamic change of the brain which occur a few seconds after the stimulation and continue for several seconds. It is very important to compare these two methodologies for combining conventional EEG studies with new findings in the brain mapping. In the present study simultaneous recording of the response of primary visual field (Vl) was done using conventional VEP and 22-channel NIRS.