In your phase! Neural phase synchronization underlies visual imagery of faces

Mental imagery is the process through which we retrieve and recombine information from our memory to elicit the subjective impression of seeing with the mind's eye. Many studies using imaging and neurophysiological techniques have shown several similarities in brain activity between visual imagery and visual perception. However, currently the dynamics of the brain in response to socially relevant stimuli, like faces, have not been studied. Elucidating brain dynamics during visual imagery of faces may help to understand the role of internal representation of socially relevant stimuli in the brain. Here we used electroencephalography to investigate brain dynamics during visual imagery of faces. We found that internal generation of visually imagined experiences is associated with long-range phase synchronization in gamma frequency band between frontal and parietal electrodes and theta frequency band between frontal electrodes. These results suggest that fronto-parietal gamma phase synchronization may be related to the endogenous binding of facial visual features transiently sustained in memory, whereas the interhemispheric frontal-theta synchrony might be encoding the memory reactivation of face stimuli.