Abstract
When the left and the right eye receive incompatible images simultaneously, the observer typically reports perceiving one of the two images at a time, with perception switching between the eyes' images over time. These switches are accompanied by transient BOLD responses occurring across the whole brain, from the highest to the lowest levels of cortical visual processing. In parallel, the chain of cognitive events surrounding a perceptual switch is a complex one, ranging from causative processes to arousal, attention and motor response selection. To assess the relative functional roles of switch-related brain responses we investigated their time course and spatial specificity in detail. We acquired simultaneous fMRI (< 1s TR) and 1kHz eye tracking data from 9 subjects during a binocular rivalry task. It is known that a considerable proportion of switches is caused by blinks and eye movements, likely due to visual transients. Our simultaneous ocular and imaging data allowed us to specifically analyze switch-related activations not tied to ocular events. We found that these endogenously caused events trigger transient BOLD responses from V1 to inferior frontal cortex. In V1, switches caused activations which are not limited to the retinotopic footprint of the binocular rivalry stimulus. Instead, these responses were retinotopically global, spanning the representation of the whole of visual space. Furthermore, switch-related response time courses from all regions had an unusual biphasic shape, starting with a strong negative dip. This temporal response profile was duplicated in the pupil's responses to these same events. By articulating the spatiotemporal elements of the brain's responses to perceptual switches, we may start to link them to their specific cognitive concomitants. Our novel findings provide insight in the brain network involved in switching during bistable perception, and allows for a fuller understanding of these networks' roles in perception and cognition.
Meeting abstract presented at VSS 2016