Saccadic Inhibition – Sudden target offset upsets saccadic generation M Stemmler1, T Stemmler2 |
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1Experimental Psychiatry, Ruhr University Bochum, Germany |
| Saccadic inhibition describes the effect on saccadic generation toward a target by sudden onset of a distractor, effectively suppressing saccade generation 90-100 ms after distractor onset. Less well established is the effect of sudden disappearance of a target. Increasing stimulus duration should lead to a decrease in response latency and increase in performance, since stimulus energy increases as well. However sudden disappearance of target may inhibit saccadic responses altering response time distribution and thereby influence performance. Here we present results of a 2 AFC experiment, in which participants had to indicate via saccade the position of an animal contained in one of two natural scenes. Stimulus duration was varied between 5 ms, 65 ms, 125 ms, 185 ms and 400 ms. Surprisingly, even if increased stimulus duration permits more information access, participants become worse in performance but nonetheless response latencies apparently decreased. Closer inspection of response time distribution reveals an observable dip in saccadic generation 120 ms after stimulus extinction, making a simple speed accuracy tradeoff unlikely. It seems saccadic response is not only inhibited by sudden appearance of a salient object but also by a salient off signal arising from stimulus offset. |
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