岩永 光一

光は,ヒトの急性な生理的反応や覚醒反応を引き起こす。最近,夜間の光反応に対する波長の依存性が報告されたがこれらの研究は,ほとんどメラトニン抑制や位相変位に関するものである。ヒトの昼間の覚醒水準に及ぼす影響を明確に示した研究はまだ少ない。本研究では,脳波と瞳孔径を測定して昼間の覚醒水準と瞳孔の反応に関する波長の効果を検討した。実験は,男子大学生10名について行なった(23±2.9歳)。単波長光条件は,420,458, 500, 550, 610, 670 nmにピークをもつ6つの干渉フィルタを使用して設定した。AAC(α波減衰係数)は, 240, 550, 610, 670nmより458nmの単波長光においてのAAC変化量が高いことが示された。このことから,昼間の458nmの単波長光暴露時の覚醒水準が高いことが示唆される。瞳孔径は,波長と時間経過の有意な交互作用(p=0.0014)が認められた。そこで,時間経過の区間毎に瞳孔径の変化を比較した結果,単波長光条件暴露16分後に,670nm単波長光暴露時の瞳孔径は458, 500, 550, 610nmのより大きくなることが示された。

By estimating the deflection velocity from the center of foot pressure (COP), this study aims to prove that the characteristics of the backward stepping reaction in the elderly are related to the strength of the antigravity muscles. The participants in this study were 10 elderly (average age 75.6+/-7.6 years) and 13 young (average age 22.0+/-2.6 years) subjects. Using force plate analysis, we measured the shift in the deflection velocity (V-RMS) and the maximum deflection velocity (V-MAX) from the beginning of the COP movement to the onset of the stepping reaction. Furthermore, we measured the strength of the antigravity muscles using a hand-held dynamometer. We correlated the V-RMS, V-MAX, and the rate of change of the deflection velocity (MAX/RMS) with muscular strength. When compared with the young subjects, the elderly showed significantly lower values of V-RMS (p<0.05) and significantly higher values of MAX/RMS (p<0.01). Furthermore, when compared with the young subjects, the elderly showed significantly lower values of muscular strength for all muscles studied (p<0.001). We established a significant correlation between the V-RMS, MAX/RMS, and muscular strength by carrying out a regression analysis (V-RMS: gluteus maximus (r=0.50, p<0.05) and rectus abdominis (r=0.48, p<0.05); MAX/RMS: adductor magnus (r=-0.66, p<0.001) and flexor digitorum longus (r=-0.62, p<0.01)). Differences were observed in the V-RMS and MAX/RMS during the backward stepping reaction; it was proposed that these differences were related to the age and muscular strength of the subjects. Therefore, further investigations should be undertaken in order to understand the effects of aging on the stepping reaction. In other words, the change-in-support strategy, including the preparatory phase of the stepping reaction, and its relationship with muscular strength should be further investigated.

本研究の目的は，後方へのステップ反応時におけるCOPの加速度値とその制御に関わる筋力との関係から，高齢者の後方ステップ反応特性について検討を加えることである。対象は後方へのステップ動作が可能な健常高齢者10名と健常若年者13名とした。分離型フォースプレートからステップ動作時の足圧中心加速度を計測し，さらにハンドヘルドダイナモメータにより抗重力筋の筋力を求めた。重回帰分析の結果，足圧中心加速度の有意な説明変数として，高齢群では長腓骨筋力と大腿四頭筋力が検出され，若年群では中殿筋力が検出された。本研究の結果から，足圧中心加速度と筋力の関係において高齢群と若年群の違いが示されるとともに，高齢群の後方ステップ反応に関与する筋力が同定された。<br>

This study was designed to investigate the physiological effects of color in terms of blood pressure and the results of electroencephalogram (EEG) as subjects looked at the sheets of paper of various colors. A questionnaire was also used to assess psychological effects. Three colors (red, green, blue) were shown to each subject in randomized order. The various colors showed distinctly different effects on the mean power of the alpha band, theta band, and on the total power in the theta-beta EEG bandwidth and alpha attenuation coefficient (AAC). Scores of the subjective evaluations concerning heavy, excited, and warm feelings also indicated significant differences between red and blue conditions. Against to our prediction, blue elicited stronger arousal than did red as expressed by the results of AAC and the mean power of the alpha band, which conflicted with the results of the subjective evaluations scores. This phenomenon might be caused by bluish light's biological activating effect. The powers of the alpha band, and the theta band, and the total power of the theta-beta bandwidth as measured by EEG showed larger values while the subjects looked at red paper than while they looked at blue paper. This indicated that red possibly elicited an anxiety state and therefore caused a higher level of brain activity in the areas of perception and attention than did the color blue. Red paper's effect to activate the central cortical region with regard to perception and attention was considerably more distinguishable than was the biological activating effect of bluish light in our study.

An electrogastrogram (EGG) is considered to be an index to the autonomic nervous system of the digestive organs. In the present study, we attempted to clarify whether or not an EGG can be used to evaluate the influence of illumination, and what kinds of effect taste stimuli and illumination have on the autonomic nervous system. In this study, we used the ratio of the normal wave component of the EGG (EGG-NR: 2-4.5 cpm power/1-10 cpm power) and the amplitude of a normal wave (EGG-M: integrated EGG of 2-4.5 cpm). Thirteen healthy males participated in 16 experimental conditions (4 lighting conditions×4 taste stimuli). The four lighting conditions were set by combinations of illuminance levels of 200 and 1500 lx and color temperatures of 3000 and 7500 K. The four taste stimuli were sweet (glucose), salty (salt), sour (acetic acid), and bitter (quinine). The changes in EGG-NR and EGG-NI were compared for different taste conditions. The results showed that EGG-NI was not significantly affected by the different taste conditions. However, the main effect of taste on EGG-NR was significant: sweet and salty tastes were significantly higher than the bitter taste. EGG-NR and EGG-NI in different lighting conditions were also compared. The main effect of different color temperatures was also significant, but the illuminance level did not affect EGG-NR. EGG-NR increased significantly at the lower color temperature. On the other hand, EGG-NI significantly increased at the lower illuminance. These results suggest that parasympathetic nervous activity has a predominant effect on gastric activity in different lighting environments. Therefore, EGG measurements may be useful indicators for illumination environment studies.

We examined the effects of monochromatic light on the time sense and the central nervous system. Nine young adult volunteers participated in this study. They were exposed to red-light and blue-light environments (illuminance was kept at 3101x). We evaluated the time sense by time-production tests of 90s and 180s and measured the P300 event-related potentials during an auditory oddball task. The 90-s time intervals produced by subjects in the two monochromatic light conditions were not significantly different. However, the 180-s time interval produced in the red-light condition (163.2±50.4s) was significantly (p&lt 0.05) shorter than that in the blue-light condition (199.0±54.4s). The peak latency of P300 in the red light (322.2±26.6ms) was found to be significantly (p&lt 0.05) shorter also than that in the blue light (332.6±20.2ms). The feelings measured by the visual analogue scales in the two light conditions were not significantly different. These results indicate that the time sense ran faster in the red-light than in the blue-light condition. We suggest that the higher activity in the central nervous system that is accounted for by the shorter latency of P300 is related to the acceleration of the time sense.

The purpose of this study was to compare the cardiovascular responses to different types of mental stress. Ten healthy males performed a mental arithmetic task (MA) on one day and were exposed to white noise (WN, 80dB) on another day. Both the MA and the WN were composed of four 5-min consecutive periods with a 3-min rest between them. On each day, the systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), cardiac output (CO), and total peripheral resistance (TPR) were measured continually during the entire experimental period. The changes from the baseline (Δ) in all periods were calculated for both mental stresses. As for the results, the δMAP, δCO, δHR, and δTPR in the MA did not significantly change during the task periods. However, in the WN, the δMAP and δTPR showed significant increases over the time of the consecutive periods. In addition, we discuss the response patterns for the two mental stresses. We examine three hemodynamic reactivity patterns: a cardiac pattern characterized by increased CO and decreased TPR, a mixed pattern characterized by a moderate increase in both CO and TPR, and a vascular pattern characterized by increased TPR and decreased CO. The results show that throughout all task/exposure periods, the response pattern remained the same for six subjects in each stress. Furthermore, of these six subjects, half showed the same response pattern in both the MA and the WN. In conclusion, compared to the MA task, consecutive WN exposure showed an accumulation of stress responses. A change in TPR contributed to a gradual increase in MAP in the WN. It is also possible that among the subjects there were different types of response to the MA and WN.

【はじめに】立位姿勢調節の評価において，身体動揺の評価は重要な役割を果たしている。近年，価格や携帯性など臨床応用の高さから，身体動揺の計測に小型の加速度計が用いられている。加速度計による身体動揺の評価は，実効値（Root mean square; RMS）などによる動揺の量の評価が行われることが多い。今回，高齢者のステップ反応時における立ち直り機能を動揺の質（微細さ）から評価を行い，その有用性について検討したので報告する。<BR>【方法】対象は日常生活動作が自立しており，側方のステップ動作が可能な高齢者9名（平均年齢75.4±7.6歳），対照群として健常学生11名（平均年齢22.5±2.7歳）とした。全ての被験者には口頭および書面にて実験の趣旨を説明し，同意を得た後に計測を行った。被験者は分離式 Force Plate（Anima製 G-6100）上で安静立位を保持後，任意の速さで重心を最大限側方に移動する。最大移動位置から非荷重側の脚を交差させ反対側のplate に接地するステップ動作を行った。Force Plateから得られる鉛直方向床反力値から安静立位（Quiet standing; QS）期と片脚支持（Single Stance; SS）期を定義した。動揺の計測には小型3軸加速度センサ（JES製 JA-30SA36-15A）を用い，第2仙椎部付近にベルトにて取り付けた。 加速度値からQS期，SS期における動揺量（RMS）と立ち直り（Zero cross point; ZCP）数を算出し，若年群との比較から高齢群の特性を検討した。RMS, ZCPともに3軸の合成成分（=√(X²+Y²+Z²)）を元に群間で比較した。なお，ZCPは加速度成分の交流波形が0レベルと交差する点であるため，今回は交流波形の傾きの変化点を元に算出した。統計手法は年代と期(QS,SS)を要因として二元配置分散分析を行い，主効果と交互作用について検討した。また，主効果が有意であった要因でWelchのt検定を行った。<BR>【結果】RMS：高齢群はQS期0.3±0.02，SS期1.1±0.5 ，若年群はQS期0.3±0.02，SS期1.1±0.6。ZCP（回/s）：高齢群はQS期15.8±1.5，SS期0.2±0.3 ，若年群はQS期16.5±2.1，SS期51.9±48.5。分散分析の結果，RMSでは期に主効果を認めた。ZCPでは年代に主効果を認め(p<0.01)，年代と期に交互作用を認めた(p<0.01)。 さらにSS期では若年群に比較し高齢群で有意に低値を得た(p<0.01)。<BR>【考察】ステップ動作におけるRMSにおいては，QS期からSS期の変化において両群間に有意な差は認めなかった。これに対しZCPでは年代と期の間に交互作用を認め，さらにQS期では両群間に差は認めず，SS期において有意な差を認めた。このことは，SS（片脚立位）期のように力学的に不安定な状態における高齢者の姿勢調節の評価には，RMSに代表される動揺の量の評価よりもZCPのような動揺の質の評価が，加齢や障害による姿勢調節への影響を見出すのに有用であることが示唆された。<BR>

The purpose of this study is to prove that the characteristics of the stepping reaction from the center of foot pressure (CFP) deflection toward the lateral direction in the elderly are related to muscular strength. Nine elderly people and eleven young students participated in this study. A subject stepped toward the lateral direction on a force plate. We measured CFP deflection characteristics of the subjects in the two groups. We measured muscular strength from the trunk to the foot using a hand-held dynamometer. We compared the CFP deflection characteristics between the two age groups. Furthermore, we observed a correlation between the muscular strength and CFP deflection characteristics in the single stance phase, which recognized a pathognomonic difference between the two groups. As compared with the young group, the elderly group showed significantly low values of deflection speed and standard deviation of deflection speed. It was suggested that the antigravity muscle extending from the planta pedis to the trunk contributed to the control of CFP deflection speed in the elderly group. Furthermore, it was suggested that the unsteadiness in the elderly was a result of a decrease in the CFP control ability due to the depression of the feedback mechanism of the sensory system with aging.

This study was designed to investigate the physiological effects of color by contingent negative variation (CNV) while looking at color cloth. Profile of Mood States (POMS) was also used to declare the psychological effects. Five stimuli colors (red, yellow, green, purple, blue), and black color as reference were shown to every subject in randomized orders. The results showed that, color effect on the late component of CNV was significant, red and green elicited significantly higher values than blue. The tension-anxiety (T-A) score of POMS also strongly showed significant differences with respect to color stimuli, while green and blue were lower than red. The correlation coefficient between POMS scores and relative values of late CNV component in terms of the ratio of each color to black reference showed that the T-A score appeared to mostly have a positive correlation with the late CNV component. In conclusion, the opposite physiological and psychological effects between red and blue cloths were confirmed, and the green cloth affected people physiologically in a similar way to the red cloth, meanwhile it affected people psychologically in the way of the blue cloth in this study.

In a system in which the operator must accomplish two or more tasks at the same time, an example of a method for preventing a serious accident would be sounding an alarm and giving a visual cue simultaneously. However, errors can come from inside or outside a system that might cause an alarm to fail. If this occurs, the operator may come to doubt or distrust the safety system, and its effectiveness is ruined. This can be very stressful for the operator's mental workload. In this study, we examined the influence of the absence of an alarm sound following some use of the system at 100% accuracy during performance of a cognitive task. We also examined the influence of the absence of the alarm as measured by EEG, HRV, and other tests as an index of mental workload. We used the difference in warning presentation rate as a way of measuring the influence on performance. The performance was the worst and the sympathetic nerve activity was highest in the 50% warning presentation rate condition, and the performance was better for where warning was not presented (0%) or at all of the presentation without fail (100%), and the relation between the warning presentation rate and the task performance showed the tendency to a reverse-u-shaped. It was suggested by this result that the absence of a warning sound brings about a decrease in a subject's performance and a rise in the operator's mental workload.

This study was intended to determine the effects of continuous bright light exposure on cardiovascular responses, particularly heart rate variability (HRV), at rest and during performance of mental tasks with acute nocturnal sleep deprivation. Eight healthy male subjects stayed awake from 21.00 to 04.30 hours under bright (BL, 2800 lux) or dim (DL, 120 lux) light conditions. During sleep deprivation, mental tasks (Stroop color-word conflict test: CWT) were performed for 15 min each hour. Blood pressure, electrocardiogram, respiratory rate, urinary melatonin concentrations and rectal temperature were measured. During sleep deprivation, BL exposure depressed melatonin secretion in comparison to DL conditions. During sleep deprivation, exposure to BL delayed the decline in heart rate (HR) for 4h in resting periods. A significant increment of HR induced by each CWT was detected, especially at 03.00 h and later, under DL conditions only. In addition, at 04.00 h, an index of sympathetic activity and sympatho-vagal balance on HRV during CWT increased significantly under DL conditions. Li contrast, an index of parasympathetic activity during CWT decreased significantly under DL conditions. However, the indexes of HRV during CWT did not change throughout sleep deprivation under BL conditions. Our results suggest that BL exposure not only delays the nocturnal decrease in HR at rest but also maintains HR and balance of cardiac autonomic modulation to mental tasks dnring nocturnal sleep deprivation.

In order to study the cognitive function rhythm related to the auditory frequency system for people who prefer to be active in the morning and at night, we conducted an experiment during morning (09:00), evening (17:00) and late-night (01:00) periods. On the basis of a morningness/eveningness questionnaire, six moderately morning-type subjects (M-types) and seven evening-type subjects (E-types) were selected. Diurnal variation of event-related potential (ERP) were assessed under low-frequency (250/500 Hz) and high-frequency (1000/2000 Hz) condition using an oddball task. M-types were tested during the morning (09:00) and evening (17:00) periods, and E-types were tested during the evening (17:00) and midnight (01:00) periods. Subjects were asked to press a button when the target stimulus was detected. We found that the P300 amplitude at 09:00 was significantly greater than that at 17:00 for M-types, was significantly greater at 17:00 than that at 01:00 for E-types. A significant difference of P300 latency and P300 amplitude was observed at 17:00 between M-types and E-types. The P300 amplitude obtained after a low-frequency stimulus was significantly greater than that after a high-frequency stimulus at 09:00 for M-types, and at 01:00 for E-types. These results revealed that stimulus frequency had effects on the diurnal changes of human cognitive function, and circadian typology had a direct effect on the diurnal change of human cognitive function. This study has extended the previous findings of auditory P300 studies on diurnal variations in terms of circadian typology and stimulus parameter.

This study was intended to determine the effects of continuous bright light exposure on cardiovascular responses, particularly heart rate variability (HRV), at rest and during performance of mental tasks with acute nocturnal sleep deprivation. Eight healthy male subjects stayed awake from 21.00 to 04.30 hours under bright (BL, 2800 lux) or dim (DL, 120 lux) light conditions. During sleep deprivation, mental tasks (Stroop color-word conflict test: CWT) were performed for 15 min each hour. Blood pressure, electrocardiogram, respiratory rate, urinary melatonin concentrations and rectal temperature were measured. During sleep deprivation, BL exposure depressed melatonin secretion in comparison to DL conditions. During sleep deprivation, exposure to BL delayed the decline in heart rate (HR) for 4h in resting periods. A significant increment of HR induced by each CWT was detected, especially at 03.00 h and later, under DL conditions only. In addition, at 04.00 h, an index of sympathetic activity and sympatho-vagal balance on HRV during CWT increased significantly under DL conditions. Li contrast, an index of parasympathetic activity during CWT decreased significantly under DL conditions. However, the indexes of HRV during CWT did not change throughout sleep deprivation under BL conditions. Our results suggest that BL exposure not only delays the nocturnal decrease in HR at rest but also maintains HR and balance of cardiac autonomic modulation to mental tasks dnring nocturnal sleep deprivation.