4th Annual Meeting of the International Multisensory Research Forum
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Andrew Bell

Neural correlates of reduced saccadic reaction times to audiovisual stimuli in the primate superior colliculus
Poster

Andrew Bell
Centre for Neuroscience Studies, Queen's University

M. Alex Meredith
Department of Anatomy, Virginia Commonwealth University

John Van Opstal
Department of Biophysics, University of Nijmegen

Douglas Munoz
Centre for Neuroscience Studies, Queen's University

     Abstract ID Number: 90
     Full text: Not available
     Last modified: May 22, 2003

Abstract
Saccades that are initiated to multimodal stimuli often have shorter latencies and increased accuracy compared to those initiated to unimodal stimuli. The intermediate layers of the superior colliculus (SC) receives converging multisensory inputs and is a critical node in the pathway mediating saccadic initiation. To identify how sensory processing in the SC contributes to reducing saccadic reaction time (SRT), particularly to multimodal stimuli, we examined three attributes of SC activity: response onset latency; saccadic threshold; and premotor activity. Single-cell activity was recorded from sensory and/or motor neurons in the intermediate layers of the SC while monkeys generated saccades to visual or audiovisual stimuli of different intensity. On audiovisual trials, the stimuli were presented simultaneously either in spatial alignment or to opposite hemifields and monkeys oriented to the visual stimulus. Spatially-aligned audiovisual stimuli elicited the shortest SRTs. These saccades were associated with an earlier onset of activity and greater premotor activity, the latter being strongly correlated with SRT. There was no observed difference in saccadic threshold. These data demonstrate how changes in SC activity related to target modality that precede the actual movment are responsible for reducing SRTs to audiovisual stimuli, emphasizing the importance of the SC in mediating multimodal orienting behaviour.


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