Abstract
Prosaccades are stimulus-driven eye movements that bring the fovea onto an area of interest. In contrast, antisaccades involve inhibiting a stimulus-driven prosaccade (i.e., response suppression) and inverting a target's spatial location (i.e., vector inversion) to mirror-symmetrical space. Previous work indicates that prosaccades are mediated via absolute visual information; however, it is possible that the top-down nature of antisaccades renders responses supported via a statistical summary representation (SSR) akin to that supporting perceptual judgments (Gillen and Heath, 2014: Vis Res). To that end, we examined whether pro- and antisaccades are differentially influenced by the weighting of target eccentricities within a stimulus-set. Participants completed pro- and antisaccades to visual targets (eccentricities of 10.5°, 15.5° and 20.5°) with and without a delay (i.e. 2,000 ms). Importantly, responses were completed in blocks wherein target eccentricities were presented with equal frequency (i.e., the control condition), and when the 10.5° (proximal weighting condition) and 20.5° (distal weighting) targets were presented five times as often as the other eccentricities. If a SSR is used to support motor output then saccade amplitude should be biased in the direction of the most frequently presented target within a stimulus-set. Results showed that prosaccades were refractory to the weighting condition manipulations, whereas no-delay antisaccades (but not their delay counterparts) showed amplitudes biased in the direction of the most frequently presented target. Accordingly, our results provide some evidence that the top-down nature of antisaccade renders endpoints specified via a SSR – visual information that is functionally distinct from prosaccades.Acknowledgments: Supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant