An Event-Related FMRI Study: Neural Substrates For Perceptual Reversal Of The Necker Cube

Ambiguous figures (such as the Necker cube and Rubins face/vase) produce a type of bistable percepts that has been used for studying visual consciousness. When human observers prolong view ambiguous figures, two percepts mutually compete for perceptual dominance so that each percept is aware for a few seconds while the other is suppressed. The process is well known as perceptual reversal or endogenous reversal. As the alternation occurs in the absence of any changes in the stimulus itself, variation in brain activity can be directly related to conscious perception. These recent results indicated a general role for fronto-parietal areas in mediating the perceptual transitions experienced during bistable figures.We examine the hypothesis by using functional magnetic resonance imaging (fMRI) and try to explore'extra'brain area possibly related to the process of perceptual reversal. The fMRI reveal that (1) in contrast to endogenous stability, event-related response were observed in fronto-parietal areas as well as temporal gyrus in endogenous reversal. However, (2) in contrast to exogenous reversal, response at higher level were observed in right temporal gyrus rather than in bilateral temporal gyrus and fronto-parietal cortex in endogenous reversal.The neural process of perceptual reversal of bistable figures is systematic interactions among fronto-parietal areas and temporal gyrus which bind functionally information together. A fronto-parietal network is required and subserves more genersal aspects in bistable visual perception. Moreover, right middle temporal gyrus may participate systemetic binding process as a key nod and contribute a important role to bistable visual perception.