Multimodal Interactions in Sensory-Motor Processing

Abstract

Abstract : Intersensory (Visual/auditory) facilitation of reaction times (RTs) was examined using three different response systems: saccadic eye movements, directed manual responses (deflections of a joystick towards the target location) and simple manual responses. The data were examined in the context of race models (in which facilitation is attributed to the minimum of two random variables representing the detection times associated with the visual and auditory targets) versus neural summation coactivation models (where the facilitation is attributed to a combination of the activities within the visual and auditory channels prior to detection). The first experiment provides evidence for neural summation coactivation in all three response model. The effects of varying combinations of auditory and visual stimulus intensity were examined in the second experiment. Intensity-dependent mismatches in the auditory and visual RTs had little effect on the magnitude of the redundant targets effect, indicating that visual-auditory integration occurs over temporal intervals of at least 40 msecs. The effects of spatial correspondence (auditory and visual targets presented in spatial register or in opposite hemifields) was examined in the third experiment. Coactivation depends upon the spatial alignment of the targets for directed responses (both saccades and directed manual responses) but not simple manual RTs; evidence of coactivation of simple RTs was found for both in register and out-of-register stimuli.