Abstract
Sensory stimuli triggered by voluntary action are perceived differently and evoke differential neural activity in sensory regions, relative to identical stimuli triggered by an external source. Such modulations are suggested to occur through corollary discharges sent from the motor system to sensory regions prior to re-afferent stimulus arrival. Given the strong laterality of the motor system, it is plausible that the magnitude of such sensory modulation will also exhibit a laterality effect, depending on the stimulus-triggering hand (right/left). In the auditory domain, we have recently provided evidence in support of such a mechanism. The aim of the current study was to further probe this model in the visual domain. In a behavioral study, 24 subjects judged the relative brightness of self-generated visual stimuli to identical stimuli triggered by the computer. Self-generated stimuli were triggered using either right or left hand and presented either in right or left visual field. Some subjects reported experiencing the self-generated stimuli as brighter and others as darker relative to the externally generated visual stimuli. However, examining the absolute modulation magnitude (proportion of trials) demonstrates that it depended on the relation between stimulus-triggering hand and stimulated visual field. In the left visual field, perception of stimuli triggered with the left hand was more strongly modulated than perception of stimuli triggered with the right hand. In the right visual field, no such effect was found. We further probed this issue using fMRI. Preliminary results from 10 subjects show differential neural response in both visual cortices for identical visual stimuli, depending on the triggering hand. Our findings support the model predicting lateralized modulation of sensory regions, consistent with the known laterality of the motor cortices.
Meeting abstract presented at VSS 2018