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Marc Zirnsak, Xiaomo Chen, Stephen Lomber, Tirin Moore; Representation of visual salience within the frontal eye field following reversible inactivation of parietal cortex. Journal of Vision 2016;16(12):13. doi: 10.1167/16.12.13.
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© ARVO (1962-2015); The Authors (2016-present)
The detection of salient stimuli is a key capacity of the primate visual system. It is widely believed that frontoparietal areas contribute to the computation of salience. For example, representations of salience have been demonstrated for neurons within parietal cortex and the frontal eye field (FEF). However, clear causal links between those representations and the emergence of salience are lacking. Here we investigate the effect of reversible inactivation of parietal cortex on the processing of salience by FEF neurons. We implanted two cryoloops within the intraparietal sulcus of a macaque to silence neuronal activity within nearby structures. Simultaneously, we recorded from FEF neurons and measured the responses to single stimuli, homogenous stimulus arrays, and pop-out arrays. Confirming the effectiveness of parietal inactivation, we observed behavioral biases consistent with deficits in humans exhibiting neglect and deficits observed in prior inactivation studies in monkeys. Specifically, eye movements were biased away from the contralateral hemifield. We observed this bias during a free-viewing task as well as during a two-target, free-choice task in which the monkey selects one of two targets presented in opposite hemifields with varying onset asynchronies. For the free-viewing task we observed a shift of the median number of fixations by 5 dva into the ipsilateral hemifield. In the free-choice task, inactivation biased choices away from the affected hemifield such that equal target choice probability was reached only when the contralateral target appeared 79 ms before the ipsilateral target. In addition, our recordings revealed a reduction in the selectivity to pop-out stimuli presented inside the receptive field of FEF neurons (-33% compared to pop-out stimuli presented outside the receptive field and -44% compared to homogenous stimulus arrays). In contrast, neuronal responses to single stimuli remained unchanged. These results suggest a dependence of visual salience signals within the FEF on parietal cortex.
Meeting abstract presented at VSS 2016
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