EEG gamma-band phase synchronization between posterior and frontal cortex during mental rotation in humans.

The main purpose of the present paper was: (1) to study the phase synchronization pattern in the gamma-band while performing the classical Shepard-Metzler task of mental rotation; (2) to investigate the role of musical training; and (3) to study hemispheric differences in the degree of synchronization during mental rotation. Multivariate electroencephalograph signals from 20 male subjects (ten musicians and ten non-musicians) were recorded while performing the mental rotation task and also at resting condition. Phase synchronization was measured by a recent index, mean phase coherence. It was found that synchronization between frontal cortex and right parietal cortex was significantly increased during mental rotation with respect to rest, whereby musicians showed significantly higher degrees of synchronization than non-musicians. Left hemispheric dominance in the degree of phase synchronization, stronger in the posterior right parietal and occipital regions, was observed in musicians. Right hemispheric dominance was generally observed in non-musicians.