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Stephen Heinen, Joel Ford, Shun-nan Yang; Cognitive expectation and repetitive priming contribute to probabilistic encoding in frontal cortex. Journal of Vision 2009;9(8):387. doi: 10.1167/9.8.387.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work demonstrated that lateral intraparietal cortex (LIP) neurons encode the probability that a given stimulus set predicts an appropriate response (Yang & Shadlen, 2007). Similarly, neurons in the supplementary eye field (SEF) probabilistically encode stimulus configurations that predict appropriate responses in a go-nogo smooth pursuit task (Heinen et al., 2008). While these neurons might calculate stimulus probabilities to form a cognitive expectation of the appropriate response, a low-level memory of recent trials (priming) could alternatively explain the result. Here, we test between these alternatives. Single neurons were recorded from the SEF in monkeys performing the ocular baseball smooth pursuit task (Kim et al., 2005). In “strike” trials, the monkey pursued targets that intersected a visible zone (plate). In “ball” trials, the monkey maintained fixation when the target did not intersect the plate. Three conditions were used, one where a block contained only strike trials or only ball trials - it allowed both the expectation and priming alternatives. In another, strikes and balls were randomized, nulling expectation, but allowing priming. Finally, strikes and balls were alternated, nulling repetitive priming, but allowing expectation. Neurons were most active during the first condition when either strategy was allowed. Activity in the other two conditions was similar, but lower than in the first condition, consistent with both expectation and priming contributing to their response. Direct assessment of activity modulation by previous trials validated the priming result. The results suggest that SEF neurons encode stimulus probabilities which signal appropriate behavior using both a cognitive expectation and a transient memory of previous trials.
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