The effects of a nighttime nap on the error-monitoring functions during extended wakefulness

Abstract

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.

Keywords: Nighttime nap; error monitoring; error positivity; error-related negativity/error negativity; night work.

Figure 1

The 4 types of arrow stimuli for the arrow orientation task. Participants were required to press the upper button for the 2 stimuli on the right (3 and 4) and the lower button for the other 2 stimuli (1 and 2). The stimuli presented in the outside positions (1 and 4) are compatible, and the other 2 (2 and 3) are incompatible.

Figure 2

Reaction time for correct responses at each task period. Error bars represent the standard errors.

Figure 3

Number of correct responses at each task period. Error bars represent the standard errors.

Figure 4

Waveforms of response-locked ERPs for erroneous responses and correct responses (A), and difference waves (B) (erroneous – correct response). ERN/Ne, error-related negativity/error negativity; Pe, error positivity.