Abstract
Visual acuity is best in the fovea and declines in the peripheral retina. Eye movements are used to project interesting objects onto the fovea, to acquire high-acuity information. Consistently, it has been shown that eye movement latencies are reduced if participants have to perform a perceptual task at the saccade target (Montagnini & Chelazzi, 2005). So far it is unknown if this facilitation is a general effect of the task, or if it depends on the gain in information by the eye movements. Here we tested if saccade latencies are sensitive to pre-saccadic peripheral visibility, post-saccadic foveal visibility or the ration of the two, which is the information gain. Observers had to foveate peripherally appearing plaid stimuli consisting of a vertical and a horizontal component and judge the orientation of the vertical component. We varied the contrast ratio of the two components while the overall contrast remained constant. To independently manipulate peripheral and foveal visibility, we changed the plaid during the saccade. Both, peripheral and foveal visibility could either be above or below previously determined individual thresholds. As a control, we measured saccade latencies without any perceptual task with varying contrast ratios. Perceptual performance followed the pattern intended by the manipulation. Without perceptual task, latencies were not influenced by the contrast ratio of the plaid. Consistently with previous reports, latencies were reduced by about 40 ms with perceptual task, even when a fast saccade was maladaptive because peripheral visibility was higher than foveal visibility. While foveal visibility did not affect latencies, there was a tendency towards reduced latencies with poor peripheral visibility. These results indicate that perceptual tasks generally facilitate eye movements, independently of peripheral and foveal visibility. This suggests that eye movement latencies are not equally modulated by informational gain as by motivational gain (Milstein & Dorris, 2007).
Meeting abstract presented at VSS 2015