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Brian J. White, Karl R. Gegenfurtner, Dirk Kerzel; Effects of structured backgrounds on the latency of saccadic eye movements. Journal of Vision 2005;5(8):585. doi: 10.1167/5.8.585.
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It has been suggested that remote distractors increase saccadic latency by increasing the firing rate of collicular fixation neurons near the time of target onset, and that the distributed network of these cells might extend as much as 10 deg from the foveal center. Since then several studies have pointed to the superior colliculus as the substrate behind an inhibited saccadic response due to non-target stimulation covering a large portion of the visual field (i.e., a display change). We examined this further by presenting a spatially continuous form of non-target stimulation (a patch of random noise) of various sizes while observers made a saccade to a simultaneously presented peripheral Gabor-target (4 c/deg, 4, 7 or 10 deg, left or right of fixation). A small patch (2.3 × 2.3 deg) of centrally displayed random noise produced a significant increase in saccadic latency consistent with the remote distractor effect. In contrast, a large patch (36 × 36 deg) did not increase latency despite the fact that it also provided raw stimulation to the region representing the fixation zone. This finding is inconsistent with several studies that show an inhibited saccadic response following a large transient onset. We also found a steady decrease in saccade latency as patch size increased from 1.6 × 1.6 deg to 4.5 × 4.5 deg. This confirms that non-target stimulation of the region representing the fixation zone is not in itself sufficient to produce the increase in latency typically found with remote distractors. The results are consistent with the idea that only a spatially confined object leads to a discharge of collicular fixation neurons.
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