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Stephen Heinen, Jeremy Badler, Shun-nan Yang; Supplementary eye field (SEF) neurons encode rules, but don't make the decision. Journal of Vision 2006;6(6):692. doi: https://doi.org/10.1167/6.6.692.
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We previously showed that SEF neurons encode the trajectory of a moving target within the context of a rule in our ocular baseball task (Kim et al., 2005). Ocular baseball is a go/nogo task in which the player predicts whether or not a moving spot target will intersect a visible “strike zone.” The player's task is to use eye movements to pursue the target if it crosses the strike zone (“strike”), or remain fixated if it does not (“ball”). Here, we studied neuronal activity during behavioral error trials to ask if SEF neurons simply encode the trajectory of the target, or whether their activity is linked to the behavioral decision. Neurons were recorded from the SEF of monkeys while they played ocular baseball. To force errors, task difficulty was altered by varying the approach angle of the target. Surprisingly, 78% of the neurons correctly signaled the target trajectory (strike or ball) even on behavioral error trials, indicating that veridical information was available to the monkey, but it was ignored. Given the apparent sensory nature of the neurons, a second experiment was done to determine if SEF neurons truly encode the rule. Here, plate size was varied (16 or 8 deg) so that the same trajectory could either be a strike or a ball. Neurons in this experiment adjusted their firing rate accordingly, evidence that the SEF can truly encode the rule-based state of an object's trajectory.
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