Abstract
When multisensory information concurrently arrives at our receptors, visual information often receives preferential processing and eventually dominates awareness and behavior. Previous research suggested that the visual dominance effect implicated the prioritizing of visual information into the motor system. In order to further reveal the underpinning neurophysiological mechanism of how visual information is prioritized into the motor system when vision dominates audition, the present study examined the time course of a particular motor activation ERP component, the lateralized readiness potential (LRP), during multisensory competition. The onsets of both stimulus-locked LRP (S-LRP) and response-locked LRP (R-LRP) were measured. Results showed that, the R-LRP onset to the auditory target was delayed about 91 ms when it was paired with a simultaneous presented visual target, compared to that when it was presented by itself. For the visual target, however, the R-LRP onset was comparable irrespective of whether it was paired with an auditory target or not. No significant difference was obtained for the onset of S-LRP. Taken together, the time courses of LRPs indicated that visual information was preferentially processed within the motor system, which coincides with the previous finding that the dorsal visual stream prioritizes the flow of visual information into the motor system.
Highlights
When faced with information from multiple sensory modalities, our brain gives unequal weight to the separate modalities
The fMRI results contrasting the Visual_Auditory and Auditory_Visual conditions showed that, when vision dominated audition, the dorsal visual stream showed increased activity, and enhanced functional connectivity with the sensorimotor cortex and inferior frontal cortex. These results together indicated that the outcome of multisensory competition depended on the dynamic interaction between sensory system and the fronto-sensorimotor system, and the visual dominance effect implicated the prioritizing of visual information into the motor system
We examine the lateralized readiness potential (LRP) time course profiles of the Visual_Auditory and the Auditory_Visual bimodal trials to reveal how information from different sensory modalities is transported to the motor system, activates motor response, and eventually determines the outcome of multisensory competition
Summary
When faced with information from multiple sensory modalities, our brain gives unequal weight to the separate modalities. The fMRI results contrasting the Visual_Auditory and Auditory_Visual conditions showed that, when vision dominated audition, the dorsal visual stream showed increased activity, and enhanced functional connectivity with the sensorimotor cortex and inferior frontal cortex These results together indicated that the outcome of multisensory competition depended on the dynamic interaction between sensory system and the fronto-sensorimotor system, and the visual dominance effect implicated the prioritizing of visual information into the motor system. It has been considered that the time between the stimulus encoding and the S-LRP onset reflected response preparation process, while the time between the R-LRP onset and the behavioral response reflected response execution process (Masaki et al, 2004; Schröter and Leuthold, 2009; Xu et al, 2015; Miller, 2016) By examining both types of LRPs, the present study unraveled at which stage of motor process the Colavita visual dominance effect emerged
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