Task-related responses (I vs C) according to time of day (MS: morning session vs. ES: evening session) and chronotype (red: morning types; blue: evening types).

<p>Displays show areas (highlighted in yellow) in which activity is associated with a task-related interaction effect between Chronotype and Session [(I vs. C)*(morning vs. evening session)*(morning vs. evening types)]. Corresponding parameter estimates (arbitrary units ± SEM) are displayed. Functional results are displayed at p<0.001, uncorrected threshold, over the mean normalized structural MR image of the population.</p

Overview of the experimental design.

<p>Subjects came to the lab 7 h before scheduled sleep time and stayed for 2 consecutive nights monitored via polysomnography (black box). They stayed under controlled light (<10 lux for wake periods and ≈0 lux for sleep periods) conditions and body posture (dashed lines). During wakefulness, sleepiness and vigilance measures were collected at hourly intervals as well as saliva samples (for melatonin assay). One and a half (morning session) and 10.5 (evening session) hours after scheduled wake up time subjects underwent an fMRI session while performing a Stroop task. Order of morning and evening sessions was counterbalanced between groups and subjects.</p

Time course of mean SWA spectral power values expressed in µV² [by 0.5 Hz bin] over the first 4 NREM-REM sleep cycles (Stage 2–4), averaged over the two experimental nights for morning (red) and evening (blue) type participants.

<p>Time course of mean SWA spectral power values expressed in µV² [by 0.5 Hz bin] over the first 4 NREM-REM sleep cycles (Stage 2–4), averaged over the two experimental nights for morning (red) and evening (blue) type participants.</p

Time course (±SEM) of (a) subjective sleepiness (KSS), (b) objective vigilance (overall median RTs on PVT) and (c) salivary melatonin in morning (red) and evening (blue) chronotypes plotted according to time spent awake.

<p>One and a half (morning session) and 10.5 (evening session) hours after scheduled wake up time subjects underwent an fMRI session. Black bars indicate scheduled sleep.</p

Regression analysis showing the relation between BOLD responses during cognitive interference (I > C; centered values) in the posterior hypothalamic region (sagittal, coronal and axial planes) and the amount of SWA (centered values) during the first sleep cycle according to the specific chronotype.

<p>Regression analysis showing the relation between BOLD responses during cognitive interference (I > C; centered values) in the posterior hypothalamic region (sagittal, coronal and axial planes) and the amount of SWA (centered values) during the first sleep cycle according to the specific chronotype.</p