Event-related theta and alpha oscillations mediate empathy for pain.

Our recent event-related potential (ERP) studies showed that phase-locked electrophysiological activities mediate both early emotional sharing and late cognitive evaluation during empathy for pain. However, whether non-phase-locked neural oscillations are involved in empathic responses remains unknown. To investigate the functional role of non-phase-locked theta (3-8 Hz) and alpha (9-14 Hz) oscillations in empathy for pain, we recorded electroencephalogram (EEG) from healthy adults who performed pain judgment of pictures of hands in painful or neutral situations. Wavelet analysis was used to calculate EEG spectral power with high time-frequency (TF) resolution. We found that, relative to neutral stimuli, painful stimuli induced increased theta event-related synchronization (ERS) at 200-500 ms but decreased alpha event-related desynchronization (ERD) at 200-400 ms, providing evidence for the engagement of theta and alpha activity in empathy for pain. In addition, subjective ratings of perceived pain and self-unpleasantness positively correlated with theta band ERS but negatively correlated with alpha band ERD related to painful stimuli, suggesting that theta and alpha oscillations are respectively involved in emotional sharing and regulation during empathy for pain. Finally, the long-latency upper theta (6-8 Hz) and alpha band TF power significantly decreased by repeated exposure to painful stimuli, indicating short-term adaptive changes of empathy-related neural activity.