Abstract
Performance on a secondary perceptual task improved when a large, random dot cinematogram (RDC) provided an alternative pursuit drive to a foveal target (Heinen et al., 2011). We hypothesized that the improvement occurred because the RDC released attention from the foveal target, implying that perception and pursuit share attentional resources. Physiological evidence demonstrates that mechanisms for the saccadic and pursuit systems overlap. Given this, we asked whether the saccadic and pursuit systems also share attentional resources. Observers pursued a small, foveal stimulus surrounded by four parafoveal target dots, and made a saccade to the target that was brightened and enlarged at a random time during the pursuit trial. The pursuit stimulus and parafoveal targets were presented alone or embedded in a large RDC moving at the same velocity. Saccade latency was shorter with the RDC present, suggesting that its benefit is not specific to the perceptual task in our earlier study. To test whether the RDC released foveal attention, we manipulated directly attention on the pursuit stimulus. Observers discriminated a brief color change applied to the pursuit stimulus 130 ms before the saccade target appeared, a time when attention to a briefly presented stimulus peaks (Nakayama & Mackeben, 1989). This eliminated the saccade latency reduction afforded by the RDC, presumably because the color change focused attention back on the fovea. However, if the color change occurred 350 ms before the saccade target appeared (when attention to a briefly presented stimulus subsides) latencies returned to the values seen with the RDC without the color change. The results suggest an RDC can release attention from foveal pursuit to facilitate saccade execution, evidence that attention for saccades and pursuit of foveal stimuli is shared.
Meeting abstract presented at VSS 2012