Event-related time-frequency analysis of the spontaneous MEG activities during 3-D object perception

Recent neuroimaging studies using functional magnetic resonance imaging (fMRI) techniques suggested the involvement of the parieto-occipital junction (POJ), the superior-occipital gyrus (SOG), and the ventral occipito-temporal junction (OTJ) in the perception of 3-D structure from motion. In this study, neuromagnetic measurement (magnetoencephalography: MEG) was used to detect the dynamic changes in the spontaneous brain activities related to 3-D structure perception from motion in humans. In this study, the event-related suppression (event-related desynchronization: ERD) of alpha and beta band spontaneous brain activities was detected in the occipital and parieto-occipital regions. The suppression of spontaneous activities was observed about 300 ms after the onset of random-dot motion, which was used as a cue for 3-D shape perception. Local suppression of alpha-band activity in occipital and parieto-occipital area was thought to indicate the engagement of these regions to the relevant sensory or cognitive iunctions, namely the perception of the structure of 3-D objects from 2-D random-dot motion.