Using Auditory and Visual Stimuli to Investigate the Behavioral and Neuronal Consequences of Reflexive Covert Orienting

Centre for Neuroscience Studies, Canadian Institutes of Health Research Group in Sensory-MotorSystems, Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada Submitted 6 November 2003; accepted in final form 17 December 2003 Reflexively orienting toward a peripheral cue can influence subsequent responses to a target, depending on when and where the cue and target appear relative to each other. At short delays between the cue and target [cue-target onset asynchrony (CTOA)], subjects are faster to respond when they appear at the same location, an effect referred to as reflexive attentional capture. At longer CTOAs, subjects are slower to respond when the two appear at the same location, an effect referred to as inhibition of return (IOR). Recent evidence suggests that these phenomena originate from sensory interactions between the cue- and target-related responses. The capture of attention originates from a strong target-related response, derived from the overlap of the cue- and target-related activities, whereas IOR corresponds to a weaker target-aligned response. If such interactions are responsible, then modifying their nature should impact the neuronal and behavioral outcome. Monkeys performed a cue-target saccade task featuring visual and auditory cues while neural activity was recorded from the superior colliculus (SC). Compared with visual stimuli, auditory responses are weaker and occur earlier, thereby decreasing the likelihood of interactions between these signals. Similar to previous studies, visual stimuli evoked reflexive attentional capture at a short CTOA (60 ms) and IOR at longer CTOAs (160 and 610 ms) with corresponding changes in the target-aligned activity in the SC. Auditory cues used in this study failed to elicit either a behavioral effect or modification of SC activity at any CTOA, supporting the hypothesis that reflexive orienting is mediated by sensory interactions between the cue and target stimuli. Address for reprint requests and other correspondence: D. Munoz, Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada (E-mail: doug{at}eyeml.queensu.ca ).