Phase re-setting of gamma neural oscillations during novelty processing in an appetitive context

Based on the previous study where phase-synchronization (PS) of gamma-band responses (GBRs) proved a reliable cerebral correlate of involuntary attention and its enhancement under threat, we measured gamma-PS elicited by novel sounds from human electroencephalogram (EEG) scalp-recordings when participants responded to visual stimuli displaying either highly motivational or neutral sceneries. We then tested the modulatory effect of the emotional conditions on auditory responses. Novel distractor sounds did not affect behavioural accuracy on subjects' visual task performance in neutral context but markedly decreased hit rate in the appetitive one. Similarly, gamma-PS to novel sounds remained intact in neutral context, whereas it showed an increase, within the 35-Hz sub-range, in the appetitive context. These results suggest that a context of processing positive emotional stimuli results into an enhanced processing of task-irrelevant novel auditory events, and, furthermore, that gamma-PS is tuned under conditions that could promote long-term survival.