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Chin-An Wang, Donald Brien, Douglas Munoz; Pupil size reveals preparatory processes in the generation of pro- and anti-saccades. Journal of Vision 2015;15(12):1310. doi: 10.1167/15.12.1310.
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The ability to generate flexible behaviors to accommodate changing goals in response to identical sensory stimuli is a signature inherited in humans and higher-level animals. In the oculomotor system, this function has often been examined using the anti-saccade task in which subjects are instructed, prior to stimulus appearance, to either look at the peripheral stimulus automatically (pro-saccade) or to suppress the automatic response and voluntarily look in the opposite direction of the stimulus (anti-saccade). Distinct neural preparatory activity has been well-documented between the pro-saccade and anti-saccade conditions, particularly in the superior colliculus (SC) and the frontal eye field (FEF), showing higher inhibition-related fixation activity in preparation for anti- compared to pro-saccades. Moreover, the level of preparatory activity related to motor preparation negatively correlated with reaction times. Pupil size is widely used to index cognitive and neural processing, a link between the SC and the pupil control circuitry has been suggested recently, showing pupil dilation evoked transiently by weak microstimulation of the SC. We hypothesize that preparatory signals in the SC should be reflected on pupil size through this pathway. Here, we examined pupil dynamics in humans during saccade preparation prior to the execution of pro- and anti-saccades. Pupil size was larger in preparation for correct anti-saccades, compared to either correct pro-saccades or erroneous pro-saccades made in the anti-saccade condition. Furthermore, larger pupil size prior to stimulus appearance accompanied saccades with faster reaction times. Overall, our results demonstrated that pupil size was modulated by saccade preparation, providing unique insight into the neural substrate coordinating cognitive processing, saccade preparation, and pupil diameter.
Meeting abstract presented at VSS 2015
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