Automatic comparison of stimulus durations in the primate prefrontal cortex: the neural basis of across-task interference

Abstract

Rhesus monkeys performed two tasks, both requiring a choice between a red square and a blue circle. In the duration task, the two stimuli appeared sequentially on each trial, for varying durations, and, later, during the choice phase of the task, the monkeys needed to choose the one that had lasted longer. In the matching-to-sample task, one of the two stimuli appeared twice as a sample, with durations matching those in the duration task, and the monkey needed to choose that stimulus during the choice phase. Although stimulus duration was irrelevant in the matching-to-sample task, the monkeys made twice as many errors when the second stimulus was shorter. This across-task interference supports an order-dependent model of the monkeys' choice and reveals something about their strategy in the duration task. The monkeys tended to choose the second stimulus when its duration exceeded the first and to choose the alternative stimulus otherwise. For the duration task, this strategy obviated the need to store stimulus-duration conjunctions for both stimuli, but it generated errors on the matching-to-sample task. We examined duration coding in prefrontal neurons and confirmed that a population of cells encoded relative duration during the matching-to-sample task, as expected from the order-dependent errors.

Neural activity in macaque medial frontal cortex represents others’ choices

“…We have described a similar switch of selectivity in a non-social context in the lPFC 32 : activity of neurons recorded in both a duration discrimination task and a match-to-sample task, with a similar task structure, switched preferences for which stimulus, the first or the second, was the longest between tasks. As for the previous study, the presence of changes in coding schemes shows the coding flexibility of prefrontal cortex 33 .…”

Determining Monkey Free Choice Long before the Choice Is Made: The Principal Role of Prefrontal Neurons Involved in Both Decision and Motor Processes

“…Many studies have examined the function of PF in decision-making, most of which have focused on tasks in which the correct response depends on the comparison between sensorial events using disparate sensory systems and domains, demonstrating how PF cells participate in decision-making (Kim and Shadlen, 1999 ; Hoshi et al, 2000 ; Freedman et al, 2001 ; Brody et al, 2003 ; Genovesio et al, 2009 , 2011 , 2012 , 2015 ; Hussar and Pasternak, 2013 ; Roy et al, 2014 ; Marcos et al, 2016 ). However, few studies have explored the influence that any pre-existing activity of PF neurons has on decision-making, and moreover, they seem to have contradictory results.…”

Low dimensional dynamics for working memory and time encoding

“…The goal of the duration-discrimination task from Genovesio et al 30,47,48 is to compare the duration of two stimuli (S1 and S2) and select the stimulus that was presented for the longest duration. The RNN for this task has four inputs (S1, S2, go-cue for S1/S2 on left/right of screen, go-cue for S1/S2 on right/left of screen) and two outputs to indicate a hand response to either the right or left ( Figure M10).…”