SUMMAR Y 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.k e y w o r d s circadian rhythm, electroencephalogram, heart rate, mental task, rectal temperature, video display terminal

ObjectivesSleep 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 MethodsFourteen 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.ResultsRestricted 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.ConclusionThe 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.

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.

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.