The Effects of a Nighttime Nap on the Error-Monitoring Functions During Extended Wakefulness

Study Objectives: To examine the effects of a 1-hr nighttime nap, and the associated sleep inertia, on the error-monitoring functions during extended wakefulness using the 2 event-related potential components thought to reflect error detection and emotional or motivational evaluation of the error, i.e., the error-related negativity/error-negativity (ERN/Ne) and error-positivity (Pe), respectively. Design: Participants awakened at 07:00 the morning of the experimental day, and performed a stimulus-response compatibility (arrow-orientation) task at 21:00, 02:00, and 03:00. Setting: A cognitive task with EEG data recording was performed in a laboratory setting. Participants: Twenty young adults (mean age 21.3 +/- 1.0 yr, 14 males) participated. Interventions: Half of the participants took a 1-hr nap, and the others had a 1-hr awake-rest period from 01:00-02:00. Measurements and Results: Behavioral performance and amplitude of the Pe declined after midnight (i.e., 02:00 and 03:00) compared with the 21:00 task period in both groups. During the task period starting at 03:00, the participants in the awake-rest condition reported less alertness and showed fewer correct responses than those who napped. However, there were no effects of a nap on the amplitude of the ERN/Ne or Pe. Conclusions: Our results suggest that a 1-hr nap can alleviate the decline in subjective alertness and response accuracy during nighttime; however, error-monitoring functions, especially emotional or motivational evaluation of the error, might remain impaired by extended wakefulness even after the nap. This phenomenon could imply that night-shift workers experiencing extended wakefulness should not overestimate the positive effects of a nighttime 1-hr nap during extended wakefulness.