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Poster C139 in Poster Session C - Friday, August 9, 2024, 11:15 am – 1:15 pm, Johnson Ice Rink
Orthogonal representations of sensory evidence and possible actions in macaque dorsolateral prefrontal cortex
Eric Kenji Lee1, Tian Wang1, Nicole Carr1, Vivian Moosmann2, Pierre Boucher1, Chandramouli Chandrasekaran1 (); 1Boston University, 2Furtwangen University
In decision-making, possible actions are often available before or after evidence for what to do is known. However, how these two pieces of information—possible actions and evidence for actions—are represented is unknown. We investigated the geometry of flexible decision-making by both recording from the prefrontal cortex of a monkey and analyzing an RNN performing the same two decision-making tasks. In each task, the goal was the same: discriminate the predominant color of a red-green checkerboard and touch the corresponding target. In one task, targets appeared before the checkerboard and in the other task, the order was reversed. Crucially, we examined the same neurons and RNN units in both tasks allowing us to jointly examine them. RNN dynamics yielded a prediction of the decision-making geometry: task variables are represented orthogonally whereas action choice output is non-orthogonal. We uncovered similar dynamical structures in the brain: after appearance of the first stim./targ., evidence and targ. config. were encoded within orthogonal subspaces of activity which then gave way to a subspace aligned action choice plane. Lastly, we show this orthogonality of task variable representation might be produced by a single-cellular mechanism in which neurons segregate into populations with selectivity for one of two task variables, but not both. Conversely, subspace alignment is the result of the same action neurons being active in both tasks.
Keywords: decision-making prefrontal cortex neural dynamics electrophysiology