Abstract
In this study spatiotemporal effects of audiovisual facilitation, and plasticity of this mechanism, were examined using a visual search task. Auditory cues preceding visual targets facilitate visual discrimination when the stimulus onset asynchrony (SOA) is short, 300ms. These crossmodal effects are spatially specific. The spatial specificity of the short-term enhancement of these effects can also be manipulated using oriented test stimuli and task irrelevant perceptual learning (TIPL), indicating that new crossmodal spatial cuing effects can be learned in the absence of focused attention (Beer, Batson & Watanabe, 2006). Additionally, there is a trend of interocular transfer with regard to the long-term inhibition of this effect for discrimination of high-level stimuli, such as faces and houses, yet no transfer or long-term effects are seen for oriented stimuli (Batson, Beer, Seitz & Watanabe, 2007). These findings suggest the involvement of more than one mechanism in the short- and long-term plasticity of audiovisual crossmodal links. To test this hypothesis, crossmodal pairings from the initial experiments (Beer, Batson & Watanabe 2006; Batson, Seitz & Watanabe 2007) will be applied to a visual search paradigm, adopted from Ahissar & Hochstein (1993; 1995). Previous experiments had only one visual stimulus per trial; therefore we will investigate the strength of both initial and learned audiovisual effects on a visual search task targeting an odd element amongst an array of distractors. In addition, TIPL sessions will be varied over conditions to test separately for plasticity of crossmodal spatial and specificity (orientation) effects. This will be done by varying location of training, and by training a subset of subjects on one of the two target orientations, respectively. Preliminary results suggest that innate audiovisual connections aid short-term facilitation in a spatially specific manner, in agreement with single-stimulus discrimination results.