Observing changes in human functioning during induced sleep deficiency and recovery periods

The duration of sleep, wakefulness and dynamic changes in human performance are determined by neural and genetic mechanisms. Sleep deprivation and chronic restriction of sleep cause perturbations of circadian rhythmicity and degradation of waking alertness as reflected in attention, cognitive efficiency and memory. In this work we report on multiple neurobehavioral correlates of sleep loss in healthy adults in an unprecedented study comprising 21 consecutive days divided into periods of 4 days of regular life (a baseline), 10 days of chronic partial sleep restriction and 7 days of recovery. Throughout the whole experiment we continuously measured the spontaneous locomotor activity by means of actigraphy with 1-minute resolution in two acquisition modes (frequency and intensity of movement). Moreover, on daily basis the subjects were undergoing EEG measurements (64-electrodes with 500 Hz sampling frequency): resting state with eyes open and closed (RS; 8 minutes long each) followed by Stroop task (ST; 22 minutes). Altogether we analyzed actigraphy (distributions of rest and activity durations), behavioral measures (accuracy and reaction times from Stroop task) and EEG (amplitudes, latencies and scalp maps of event-related potentials from Stroop task and power spectra from resting states). The actigraphy measures clearly indicate rapid changes after sleep restriction onset, confirming our former investigations - the novel insight is a slow and incomplete relaxation to the original locomotor behavior. The pattern of partial recovery appears also in accuracy (in ST) and power of delta rhythm (in RS). The impact of sleep loss is also evident in reaction times (in ST), yet followed by complete recovery, and finally in ERP amplitudes and latencies, which however did not return to the baseline at all. The results indicate that short periods (a few days) of recovery sleep subsequent to prolonged periods of sleep restriction are overall insufficient to recover fully.