Toshinori Kobayashi

An ERP investigation of emotional processing in European and Japanese individuals

This article examined neural time course differences in the processing of emotional pictures in European and Asian individuals. Event-related potentials (ERPs) were recorded in 15 French and 15 Japanese volunteers during the presentation of neutral and emotional pictures in their own country. ERPs were analyzed by means of spatio-temporal Principal Component Analysis (PCA) and allow to evaluate cultural influences on emotional processing along three temporal windows: 105 to 140 ms, 176 to 230 ms and 255 to 455 ms. Main results highlight that (1) early ERP components coded emotional charge but were not modulated by cultural background, (2) later components showed a significant decrease of amplitudes at parieto-occipital areas for Japanese participants compared to French ones in emotional condition. These findings suggest that, in both populations, similar neurocognitive processes are involved in the early stage of the emotional stimuli processing and effects observed on later components may reflect a poorer engagement of parietal areas, known to be involved in emotional arousal dimension. Considering that cognitive judgments were similar in both populations, electrophysiological findings suggest that cultural influences on later stage of emotional processing could be related to the known lower level of emotionally expressive behavior in Japanese than in Caucasians.

Effects of daytime activity upon the timing of REM sleep periods during a night

Abstract The effects of mental and physical daytime activities upon REM sleep cycle (REM cycle) during 1 night was studied in five university students (aged 19–25 years). Mental activity with high tension has effects upon the timing of REM sleep periods in the later part of the night. Physical activity has effects upon the timing of REM sleep in the early part of the night. The result suggests that mental and/or physical activities during daytime modulate REM cycle during the night.

Sleep behavior of pregnant women using sleep log

Abstract Sleep log study, which was designed to study sleep characteristics by questionnaire, was performed on 172 pregnant women about the relationship between their pregnancy and their night sleep. Sleep behavior by sleep log revealed that they woke more frequently during the course of their pregnancy and that their total sleep time decreased gradually toward the end of their pregnancy. According to their subjective evaluations, these shortages of night sleep could not be made up with the morning naps in the multiparas as was the case of the primiparas. These changes in sleep characteristics have been studied from biological, psychological and social factors view points.

Alpha-delta sleep in a case with non-24 h sleep-wake syndrome: Quantitative electroencephalogram analysis of alpha and delta band waves

Abstract  Four all‐night polysomnograms of a 39‐year‐old male patient with non‐24 h sleep‐wake syndrome were recorded. We analysed electroencephalograms (EEG) with the power spectrum method and the wave pattern recognition analysis of Fujimori. The EEC of the rest waking condition showed normal patterns. High‐voltage diffuse alpha band waves were observed in sleep stages 2, 3 and 4. The integrated area of the alpha band waves in the analysis epochs showed a strong positive correlation to the delta hand components in the power spectrum of the same epoch during sleep (correlation coefficients r= 0.762–0.815). Alpha hand waves during sleep were clearly different from the alpha waves in the rest waking condition, with respect to slower peak frequency and the frontal dominant voltage distribution.

Effects of daytime activities on sleep qualities

Abstract In order to study effects of daytime activities on sleep, eleven healthy male university students (aged 9–25) spent three different activities days; the mentally and physically relaxation day, the mental active day, and the physical active day. Their sleep were recorded in the nights after these three different days. The large amount of slow wave sleep (SWS) concentrated on the first sleep cycle in the night after the physically active day. The individual differences in body temperature curve during a night became large in the order of the night after the physical active day, the night after the mental active day, and the night after the mentally and physically relaxation day. These results suggest that an active day not only leads to a good quality of sleep, but also stabilizes the circadian body temperature curve.

Individual differences on diurnal variations of the task performance

Abstract In order to understand psychophysiological background of the individual differences on the diurnal variation of task performance, the task performance (i.e. the number of a simple adding calculation performed in one minute) was measured from 09:30 in the morning to 21:30 in the late evening for 9 healthy university male students. Heart rate (HR) and body temperature were also continuously recorded for 35 hours. There were two different types in the diurnal variation of the task performance; the morning type who shows the best performance in the morning, and the evening type who shows it in the evening. The body temperature curve during daytime in the evening type goes gradually up to the evening, on the contrary, that in the morning type rapidly rises to the maximum point in the morning or the afternoon. HR during daytime were higher in the morning type than the evening type. These results indicate that the morning type has a tendency of the higher mental tension compared with the evening type. And they also suggest that the individual differences on the task performance with a large mental concentration are caused by some kinds of subjects psychosomatic state.

Sleep Package Model: mathematical model for a sleep pattern

Abstract In order to design the better sleep-wake schedule for shift workers, the mathematical model for sleep called SLEEP PACKAGE MODEL was developed. When we get three parameters; time to fall asleep (t), the length of sleep period (Ls), and the waking time (Tw) before a sleep are given, the model can predict the sleep pattern, namely NonREM-REM cycle pattern. In order to examine the ability of the model, the sleep patterns for 60 nights of 20 male young adults were recorded under the usual night condition (t=23:00, Ls=8 hrs, and Tw=16 hrs), and the recovery sleep of one university male student was recorded after the 72 hrs sleep deprivation condition (t=09:00,Ls=10 hrs, and Tw=72 hrs). The usual night sleep and the recovery sleep after sleep deprivation were predicted by the model. The estimated sleep patterns by the model were compared with the actual sleep pattern in the experiment, as the results, the estimated sleep patterns by the model is very similar to the acutal sleep patterns. So thatm the result suggests that the application of this model to human engineering field could be expected.

Diurnal Emotional States Impact the Sleep Course.

Background Diurnal emotional experiences seem to affect several characteristics of sleep architecture. However, this influence remains unclear, especially for positive emotions. In addition, electrodermal activity (EDA), a sympathetic robust indicator of emotional arousal, differs depending on the sleep stage. The present research has a double aim: to identify the specific effects of pre-sleep emotional states on the architecture of the subsequent sleep period; to relate such states to the sympathetic activation during the same sleep period. Methods Twelve healthy volunteers (20.1 ± 1.0 yo.) participated in the experiment and each one slept 9 nights at the laboratory, divided into 3 sessions, one per week. Each session was organized over three nights. A reference night, allowing baseline pre-sleep and sleep recordings, preceded an experimental night before which participants watched a negative, neutral, or positive movie. The third and last night was devoted to analyzing the potential recovery or persistence of emotional effects induced before the experimental night. Standard polysomnography and EDA were recorded during all the nights. Results Firstly, we found that experimental pre-sleep emotional induction increased the Rapid Eye Movement (REM) sleep rate following both negative and positive movies. While this increase was spread over the whole night for positive induction, it was limited to the second half of the sleep period for negative induction. Secondly, the valence of the pre-sleep movie also impacted the sympathetic activation during Non-REM stage 3 sleep, which increased after negative induction and decreased after positive induction. Conclusion Pre-sleep controlled emotional states impacted the subsequent REM sleep rate and modulated the sympathetic activity during the sleep period. The outcomes of this study offer interesting perspectives related to the effect of diurnal emotional influences on sleep regulation and open new avenues for potential practices designed to alleviate sleep disturbances.

Pre-sleep emotional induction affects REM rate and sympathetic activity during sleep

Background: Insufficient sleep is linked to enhanced risk of developing hypertension; however, the mechanism by which this occurs is currently unknown. In this study we sought to evaluate the effects of experimental sleep restriction on spontaneous baroreflex sensitivity. Methods: Five healthy subjects (4 female; age 23 ± 1 years) underwent a 4-day period of acclimation followed by 9 days of experimental sleep restriction (4 hours of sleep per night – from 12:30 AM to 4:30 AM). Beat-by-beat heart rate (HR, ECG) and blood pressure (BP, Finometer) were measured during 15 minutes of quiet rest. Spontaneous cardiac baroreflex (BRS) sensitivity was determined using spectrum analysis. Subjects were studied on Day 2 (Acclimation) and Day 13 (Restriction). Results: Resting BP and HR were not different between acclimation and experimental sleep restriction (SBP: 127 ± 5 vs 133 ±3 mmHg, p = 0.13; DBP: 79 ± 2 vs 80 ± 4 mmHg, p = 0.21; HR: 68 ±3 vs 73± 4 BPM, p = 0.8). BRS gain was significantly blunted during sleep restriction when compared to the acclimation period (18 ± 2 vs 13 ± 2%, p b 0.01). Conclusion: Acute experimental sleep restriction in young healthy adults results in a reduction of cardiac baroreflex sensitivity prior to obvious/overt changes in resting BP. These data suggest that impaired baroreflex function may be an early contributing factor to the high prevalence of hypertension and cardiovascular diseases in the sleep deprived general population.

Study of individual differences in ERP by multivariate analysis of a few single trial ERPs

Abstract The study of Event-related potentials(ERPs) has contributed to the understanding of human psychological functions. ERPs are postulated to be multi-component electrical activities of the brain. In our previous paper, the single trial CNV data measured at each electrode site under constant experimental conditions were analyzed by PCA - Varimax rotation - Multiple regression analysis. However, such a method requires a lot of single trial CNV samples to estimate the clearer CNV components. The purpose of the present study is to compare the differences in CNV components between individual subjects. In order to extract satisfactory CNV components from few single trial data, the CNV samples were multiplied by uniform pseudo-random numbers generated by computer. The results indicated that the CNV components of each subject have specific waveshape and amplitude.