The effect of sleep deprivation on empathy for pain: An ERP study.

Empathy for pain has a strong adaptive function. It plays a protective role in survival and exerts a vital impact on successful social interaction. Sleep loss, however, is commonplace in current society, and people are increasingly plagued by it. Previous studies have investigated whether sleep loss affects empathy for pain, yet the results were undecided. We aimed to determine whether this effect is existed and further explore the temporal and frequency dynamics of neural activities involved in this effect by recording the electroencephalogram (EEG) signals. We recruited 25 healthy adults (11 females) who were required to perform a pain judgement and unpleasantness rating about the presented nociceptive and neutral pictures after nocturnal sleep (NS) and sleep deprivation (SD), and their neuronal activities were recorded by event-related potentials (ERPs). Results showed a significantly decreased amplitude in the early components (N2, N340) of vicarious pain processing after SD. In further time-frequency (TF) analysis, a reduced energy occurred in theta2 (5-7 Hz) band under SD condition. Moreover, the decreased theta2 was positively correlated with the subjective ratings of both other's pain and self-unpleasantness only under SD condition. Our results indicated that SD impairs affective sharing of empathy for pain.