doi: 10.1111/j.1365-2869.2009.00800.x Sleep history affects task acquisition during subsequent sleep restriction and recovery TRACY L. RUPP, NANCY J. WESENSTEN and THOMAS J. BALKIN Department of Behavioral Biology, Walter Reed Army Institute of Research, Silver Spring, MD, USA Accepted in revised form 10 September 2009; received 01 July 2009 SUMMARY The aim of the present study was to examine if sleep amount prior to sleep restriction mediated subsequent task acquisition on serial addition ⁄ subtraction and reaction time (RT) sub-tasks of the Automated Neuropsychological Assessment Metric. Eleven males and 13 females [mean (SD) age = 25 (6.5) years] were assigned to either an Extended [10 h time in bed (TIB)] (n = 12) or Habitual [Mean (SD) = 7.09 (0.7)] (n = 12) sleep group for 1 week followed by one baseline night, seven sleep restriction nights (3 h TIB) and five recovery nights (8 h TIB). Throughout baseline, restriction and recovery, mathematical and serial RT tasks were administered hourly each day (08:00–18:00 h). Math and serial RT throughput for each task (speed · accuracy product) was analysed using a mixed-model anova with fixed effects for sleep group, day and time-of-day followed by post hoc t-tests (Bonferroni correction). Math throughput improved for both groups during sleep restriction, but more so compared with baseline for the prior sleep Extended group versus the Habitual group during recovery. In sum, 1 week of sleep extension improved resilience during subsequent sleep restriction and facilitated task acquisition during recovery, demonstrating that nightly sleep duration exerts long- term (days, weeks) effects. keywords chronic sleep restriction, learning, partial sleep deprivation, recovery, sleep extension INTRODUCTION In an increasingly 24-h society, occupational and personal demands often conflict with obtaining adequate sleep. Conse- quences of sleep restriction include cognitive deficits such as learning and memory impairments (e.g. Stickgold et al., 2001; Walker et al., 2003). Previous studies on learning and sleep have primarily focused on total sleep deprivation; the conse- quences of long-term sleep restriction and recovery sleep on task acquisition remain unclear. Also unclear is the effect of sleep ÔdebtÕ prior to sleep restriction, and if prior sleep extension (e.g. Ôpaying backÕ the debt) may improve task acquisition by providing greater cognitive reserves during sleep loss. Performance deficits from sleep loss have been described in the context of a two-process model (Borbe`ly, 1998), with the homeostatic process as a simple reservoir in which perfor- mance capacity increases exponentially during sleep and decays linearly or exponentially during wakefulness. Accord- ing to Johnson et al. (2004), this simple reservoir conception is accurate for describing and predicting performance with acute total sleep deprivation (in which recovery generally occurs after one night of recovery sleep), but not with periods of recovery following chronically restricted sleep. This notion was supported by findings from a sleep restriction study by Belenky et al. (2003), showing large individual differences in perfor- mance during sleep restriction and in rate of recovery, with sleep-restricted volunteers failing to recover to baseline levels with three recovery nights. One explanation set forth for these findings was that volunteers were not entering the study in comparable states due to differing prior habitual sleep sched- ules. Results from a recent follow-up sleep restriction study have demonstrated that prior sleep extension does indeed improve performance and alertness during subsequent sleep restriction and recovery (Rupp et al., 2009). Here we present Correspondence: Tracy L. Rupp, PhD, Walter Reed Army Institute of Research, Department of Behavioral Biology, Rm 2w88, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA. Tel.: +1-301-319- 9352; fax: +1-301-319-9979; e-mail: tracy.rupp@amedd.army.mil J. Sleep Res. (2010) 19, 289–297 Sleep deprivation and memory Published 2009 This article is a US government work and is in the public domain in the USA 289