Modeling circadian and sleep-homeostatic effects on short-term interval timing

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 short-term 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

Sleep Deprivation Influences Diurnal Variation of Human Time Perception with Prefrontal Activity Change: A Functional Near-Infrared Spectroscopy Study

Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well as cortical areas involving the prefrontal cortex (PFC). It has also been reported that the PFC is vulnerable to sleep deprivation, which has an influence on various cognitive functions. The present study is aimed at elucidating the influence of PFC vulnerability to sleep deprivation on short-time perception, using the optical imaging technique of functional near-infrared spectroscopy. Eighteen participants performed 10-s time production tasks before (at 21:00) and after (at 09:00) experimental nights both in sleep-controlled and sleep-deprived conditions in a 4-day laboratory-based crossover study. Compared to the sleep-controlled condition, one-night sleep deprivation induced a significant reduction in the produced time simultaneous with an increased hemodynamic response in the left PFC at 09:00. These results suggest that activation of the left PFC, which possibly reflects functional compensation under a sleep-deprived condition, is associated with alteration of short-time perception

Preferable Forms of Relaxation for Health Promotion, and the Association between Recreational Activities and Self-perceived Health

Little research has been done on the association between relaxation and health. In the present study, by conducting a nationwide cross-sectional survey, we aimed to obtain scientific data on the preferable forms of relaxation for health promotion, and to clarify the associations between specific recreational activities and self-perceived mental and physical health. We selected 4,000 households by stratified random sampling from across Japan in November 2009 and used the interview method to collect data (number of subjects:2,206). The questionnaire contained items on sleep, recreation status, recreational activities, and self-perceived mental and physical health status. We obtained responses from 1,224 adults (response rate:55.5%). Insufficient rest from sleep, short sleep duration (＜6h/day), ineffective use of free time, and less free time used for activities other than rest showed independent positive associations with poor mental and physical health. The results of the logistic regression analyses showed significantly low adjusted odds ratios with regard to the status of poor mental and physical health for outings/walking among men (0.33 [95% confidence interval;0.16-0.68] and 0.49 [0.26-0.90], respectively), and for community activities among women (0.19 [0.04-0.79] and 0.27 [0.09-0.77], respectively). Relaxation for the promotion of health should include both passive relaxation (rest) and active relaxation (recreation). In addition, ensuring sufficient sleep duration is important for passive relaxation, and engaging in outings/walking for men and community activities for women are important for active relaxation

Change in hemodynamic response and functional correlation in prefrontal cortex (PFC) activity after sleep deprivation.

<p>(A) Topographic image representing increased activation in the PFC on day 2 in the SD condition (n = 14). The image is constructed by using subtracted values between the SC and the SD conditions (SD minus SC). The area of dotted white circles emphasizes the left anterior PFC (LAPFC) including chs. 17, 21 and 22 for region of interest (ROI) analysis. (B) Correlation between normalized produced intervals and oxy-Hb concentration changes in the LAPFC ROI on day 2 in the SD condition (n = 14). Functional connectivity in changes of short-time perception with LAPFC activity under sustained wakefulness is suggested by a correlation coefficient (<i>r</i>) of 0.535 with statistical significance (<i>p</i><0.05).</p

Approximate positions of 22 channels in fNIRS superimposed on the 3D head model.

<p>The 22 measuring channels were produced by optodes placed equidistantly over the prefrontal cortex (PFC) area. The lower line of the 3×5 optode probe was positioned along the reference curve linking T3, T4 and Fpz.</p

Mean interval variation in SC and SD conditions (n = 18).

<p>Black filled triangles with error bars (left: day 1, right: day 2) and the linking line indicate mean produced intervals and the trend of fluctuation in the SC condition, respectively. Gray filled circles with error bars (left: day 1, right: day 2) and the linking line show mean produced intervals and the trend of variation in the SD condition, respectively. Solid curves connecting two markers indicate significant differences (<i>p</i><0.05).</p