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B. J. White, R. A. Marino, S. E. Boehnke, L. Itti, J. Theeuwes, D. P. Munoz, Interactions between endogenous and exogenous neural activity in the superior colliculus, In: Proc. Society for Neuroscience Annual Meeting (SFN'07), Nov 2007.
Abstract: The oculomotor capture paradigm (Theeuwes et al. 1999) is an ideal tool to explore goal driven target selection without the contamination of visual transients on the goal related activity. Using this task, we explored neural correlates of the interaction between stimulus-driven and goal-driven oculomotor behavior in the superior colliculus (SC). Two monkeys were trained on the task in which one of six stimuli, equidistant from fixation, becomes a target singleton through an isoluminant color change in the remaining five items. Simultaneously, on half the trials an additional abrupt-onset distractor appeared either near or far from the saccade goal. The monkeys were required to make a saccade to the odd colored target. Behaviorally, the results were not unlike that found in humans. Correctly directed saccades showed longer latencies on distractor-present trials and shorter latencies when the eyes were overtly captured by the distractor. In addition, the proportion of errors to the abrupt-onset distractor and other non-target items was always greatest when the distractor appeared near the goal of the saccade. We recorded single unit activity in the intermediate SC and found that pretarget activity could predict whether the monkey would subsequently make an error. In addition, on correctly directed saccades where the abrupt-onset distractor appeared near the goal of the saccade, there was a suppression of the endogenous-related activity that was not evident in the remote distractor condition. This suppression was also correlated with the increase in saccade latency. The results are consistent with the hypothesis that endogenous and exogenous activity is combined in the intermediate SC, and compete through lateral interactions to guide oculomotor behavior.
Themes: Monkey Electrophysiology, Human Eye-Tracking Research
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