Figure 1.

Overview of the experimental protocol. Eight participants were measured in a modified constant routine protocol over 2 experimental days. Counterbalanced across individuals, participants underwent a night of normal sleep (NS) or total sleep deprivation (SD) on the night prior to each experimental day. Vigilance was measured five times per day (block 1-5) at regular intervals using the Brief Stimulus Reaction Task (BSRT).⁸ Each of the five daily blocks was identical, and consisted of the following procedures: restroom break, isocaloric meal and drink (300 kcal per block), and rest period comprised the first half hr of each block, after which a computerized task battery was started. In each block participants performed the BSRT sustained attention task. Output measures were reaction speed and lapses, defined as lack of responses, including responses slower than the 10^th percentile calculated on the well rested day.