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Jessica Heeman, Stefan Van der Stigchel, Jan Theeuwes; Bimodal latency distribution and distractor effects in Express Saccades in humans.. Journal of Vision 2016;16(12):854. doi: 10.1167/16.12.854.
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© ARVO (1962-2015); The Authors (2016-present)
It is well known that under specific conditions, saccades can be made with extremely short latencies (about 110 to 130 ms). These so-called Express Saccades (ES) have been observed in animals showing two separate peaks in the saccade latencies distributions. Up till now, separate peaks in the distribution have not been observed in human observers. In two experiments we investigated the saccade latency distribution while examining two well-known target-distractor interactions. We examined the Global Effect (GE) which occurs when a distractor is presented in close proximity of the target. Typically, saccades tend to land at a location between target and distractor. In addition we examined the Remote Distractor Effect (RDE), an effect which describes the longer saccade latencies when a distractor is presented further away from a target. In both experiments participants made saccades to a sudden onset target. In some trials the target was accompanied by a distractor close or remote from the target. A gap-paradigm ensured a high percentage of low latency saccades. In Experiment 1, participants were given a 100% valid cue and a warning tone to indicate the impending target and its location and qualitative feedback on the response time. In Experiment 2 the timing was identical but we presented no cue, no warning toine and neutral feedback was provided. The paradigm triggered high percentages of ES. Extraordinarily, the latency distribution in Experiment 1 showed two distinct, separate peaks. This suggests that, as has been suggested based on animal studies, a separate process that results in ES is involved in the processing of early visual information in human observers. In addition, results show a GE and a RDE, even for the fastest visually triggered saccades. This indicates that endogenously prepared ES are not immune to exogenous influences and are moderated by early visual input.
Meeting abstract presented at VSS 2016
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