Chronic sleep deficit and performance of a sustained attention task--an electrooculography study.

Electrooculography (EOG) was used to explore performance differences in a sustained attention task during rested wakefulness (RW) and after 7 days of partial sleep deprivation (SD). The RW condition was based on obtaining regular sleep, and the SD condition involved sleep restriction of 3 h/night for a week resulting in a total sleep debt of 21 h. The study used a counterbalanced design with a 2-wk gap between the conditions. Participants performed a sustained attention task for 45 min on four occasions: 10:00-11:00, 14:00-15:00, 18:00-19:00, and 22:00-23:00 h. The task required moving gaze and attention as fast as possible from a fixation point to a target. In each session, 120 congruent and 34 incongruent stimuli were presented, totaling 1232 observations/participant. Correct responses plus errors of omission (lapses) and commission (false responses) were recorded, and the effect of time-of-day on sustained attention following SD was investigated. The analysis of variance (ANOVA) model showed that SD affected performance on a sustained attention task and manifested itself in a higher number of omission errors: congruent stimuli (F((1,64)) = 13.3, p < .001) and incongruent stimuli (F((1,64)) = 14.0, p < .001). Reaction times for saccadic eye movements did not differ significantly between experimental conditions or by time-of-day. Commission errors, however, exhibited a decreasing trend during the day. The visible prevalence of omissions in SD versus RW was observed during the mid-afternoon hours (the so-called post-lunch dip) for both congruent and incongruent stimuli (F((1,16)) = 5.3, p = .04 and F((1,16)) = 5.6, p = .03, respectively), and at 18:00 h for incongruent stimuli (F((1,13)) = 5.7, p = .03).