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要旨:
The relationship between brain activity and conscious visual experience is central to our understanding of the neural mechanisms underlying perception. Binocular rivalry, where monocular stimuli compete for perceptual dominance, has been previously used to dissociate the constant stimulus from the varying percept. We report here fMRI results from humans experiencing binocular rivalry under a dichoptic stimulation paradigm that consisted of two drifting random dot patterns with different motion coherence. Each pattern had also a different color, which both enhanced rivalry and was used for reporting which of the two patterns was visible at each time. As the perception of the subjects alternated between coherent motion and motion noise, we examined the effect that these alternations had on the strength of the MR signal throughout the brain. Across the different visual areas, we have found varying degrees of correlation between the neural activity and the visual percept. Areas V3A, V5 (MT) and LOC showed a much stronger activation when subjects perceived coherent motion than when they perceived motion noise. A similar but not as strong an effect was observed in area V3, whereas a much less pronounced difference between the two conditions was found in areas V1, V2 and V4. These results demonstrate that motion perception is able to modulate the activity of most visual areas known to be involved in motion processing. Instead of a clear distinction between ‘processing’ and ‘perceptual’ areas, we found a gradual increase in the correlation between neural and perceptual events as one moves towards the higher areas of the motion pathway. We thus conclude that the areas involved in the processing of a specific visual attribute are also part of the neuronal network that is collectively responsible for its perceptual representation.
