Localizing the Neural Substrate of Reflexive Covert Orienting

The capture of covert spatial attention by salient visual events influences subsequent gaze behavior. A task irrelevant stimulus (cue) can reduce (Attention capture) or prolong (Inhi-bition of return) saccade reaction time to a subsequent target stimulus depending on the cue-target delay. Here we investigated the mechanisms that underlie the sensory-based account of AC/IOR by manipulating the visual processing stage where the cue and target interact. In Experiment 1, liquid crystal shutter goggles were used to test whether AC/IOR occur at a monocular versus binocular processing stage (before versus after signals from both eyes converge). In Experiment 2, we tested whether visual orientation selective mechanisms are critical for AC/IOR by using oriented “Gabor” stimuli. We found that the magnitude of AC and IOR was not different between monocular and interocular viewing conditions, or between iso- and ortho-oriented cue-target interactions. The results suggest that the visual mechanisms that contribute to AC/IOR arise at an orientation-independent binocular processing stage.