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Chin-An Wang, Douglas Munoz; Superior colliculus coordinates pupillary and saccadic responses. Journal of Vision 2017;17(10):740. doi: https://doi.org/10.1167/17.10.740.
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The appearance of a salient stimulus in the environment evokes a series of responses to orient the body for appropriate action. These responses include eye movements and pupil dilation that may be coordinated by the midbrain superior colliculus (SC). The role of the SC on saccade and pupil dilation has been separately established, but whether these responses are linked is still unknown. Here, we investigated the coordination between saccadic and pupillary responses through microstimulation of the SC with manipulating stimulation parameters and background luminance. Parameters of SC microstimulation are known to systematically modulate properties of evoked saccades. If the orienting responses are coordinated by the SC, the similar modulation should be observed in pupil size by varying stimulation train frequency and duration (frequency: 150-300 Hz; stimulation train duration: 25-100 ms). While requiring monkeys to maintain central fixation, we stimulated the intermediate SC layers. Varying train frequency and duration systematically modulated saccadic as well as pupillary responses. Importantly, the positive trial-by-trial correlation between two responses was observed within individual stimulation condition. Trials with larger saccadic responses had larger pupillary responses, and larger pupil responses were observed on trials with evoked saccades, compared to trials without evoked saccades. These results together suggest that the same output signals from the intermediate SC project to both pupil and saccade premotor circuits to initiate coordinated responses. Background luminance influenced pupillary but not saccadic responses, characterizing the pupil-specific modulation. Together, our results demonstrate coordinated orienting movements of saccade and pupil size through the SC, importantly extending an integrated role of the SC among various orienting movements.
Meeting abstract presented at VSS 2017
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