The effects of a 10-day partial sleep deprivation and the following recovery on cognitive functioning – a behavioural and EEG study

Sleep deprivation is an important societal problem that affects millions of people around the world on a daily basis. Our study aimed to examine the impact of a partial sleep restriction and following recovery processes on cognitive information processing, as evaluated by the Stroop test. We tested 15 participants over a period of 21 consecutive days, divided into 3 sleep conditions: 4 days of typical daily routine (baseline, ‘base’), 10 days of partial sleep deprivation (‘SD’), and 7 days of recovery (‘rec’). Each day, participants took part in an EEG experiment in which they performed a Stroop test, lasting for about 30 minutes, that required them to make an appropriate response to congruent and incongruent stimuli. Additionally, every day they answered a number of questions regarding their subjective levels of sleepiness and mood. During the whole period of 21 days, participants’ spontaneous locomotor activity was measured with the use of actigraphy. We have found behavioural and neural changes associated with different sleep conditions, such that the 10-day period of partial sleep restriction was linked with poorer behavioural performance on the Stroop test and an attenuated P300 neural response, compared to the baseline, followed by the observation of slow and gradual return in the period of recovery. This study, the first longitudinal study of its kind, shows that partial sleep deprivation has detrimental, long-term consequences on both behavioural and neural levels. This adds to the growing body of literature on this important issue in modern societies. Summary Sleep deprivation, a world-wide problem in the 21st century, is associated with a number of complications, such as motor vehicle accidents (Lyznicki et al., 1998; Goel et al., 2009), medical errors (Barger et al., 2006), poorer health (in Colten & Altevogt, 2006), as well as cognitive deficits including problems with working memory and attention (van Dongen et al., 2003; Lim & Dinges, 2008). While total sleep deprivation (that is, a complete lack of sleep in a 24-hour period) is usually reserved only to certain professions (such as medical doctors), partial sleep restriction (that is, reducing one’s sleep time in a 24-hour period to fewer hours than typically required) is world-wide and affects a large proportion of the population across the globe. Taking this global impact into account, and thus increasing our understanding of the neurophysiological and cognitive processes that are linked with partial sleep deprivation, could largely inform the public discussion over what kind of impact, if any, restricting our sleep has on our daily functioning. This 21-day long EEG study investigated the effects of a prolonged (10-day) sleep restriction, and the recovery processes (over a 7-day period) that followed. Each day participants performed a Stroop test, known to measure attentional levels, and completed a number of sleep-related questionnaires. We have found that while behavioural responses are easier to recover, the neurophysiological responses are heavily affected after a period of sleep deprivation, with one week of recovery being insufficient to return to a pre-testing performance of an individual.