Contrasting Roles for Orbitofrontal Cortex and Amygdala in Credit Assignment and Learning in Macaques.
Bottom Line: Recent studies have challenged the view that orbitofrontal cortex (OFC) and amygdala mediate flexible reward-guided behavior.A second experiment confirmed the existence of signals for adaptive stay/shift behavior in lOFC and reflecting irrelevant reward in the amygdala in a probabilistic learning task.Our data demonstrate that OFC and amygdala each make unique contributions to flexible behavior and credit assignment.
Affiliation: Department of Experimental Psychology, University of Oxford, OX1 3UD, Oxford, UK; Department of Psychology, The University of Hong Kong, Pokfulam Road, Hong Kong. Electronic address: email@example.com.Show MeSH
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Mentions: Four monkeys performed the deterministic ODR task (experiment 1; Figure 1A); they had to discriminate which of two options led to a reward at the beginning of a session. The reward assignment reversed after the monkeys performed the 50th rewarded trial and then it reversed again after the 100th rewarded trial. The daily session stopped after the monkey performed 150 rewarded trials in total (Figure 1B). The animals encountered new stimuli at the beginning of each day of testing. On average, the monkeys performed 183.4 trials (81.8% correct) in each session and each monkey contributed four to six sessions in this dataset. To investigate the animals’ behavior, we split each session into three blocks (block 1: the initial learning period before any reversals; blocks 2 and 3: after the first and second reversal, respectively) and calculated the average accuracy of each trial as a function of its position in the block (trial 1, trial 2, trial 3, and so on; Figure 1C). The monkeys typically showed poor accuracy on early trials but they were consistently above 50% correct after the ninth trial of a block (t3 > 3.920, p < 0.030; Figure 1C). When block 1 and blocks 2 + 3 were analyzed separately, the first trials of block 1 had a higher accuracy (38%), due to random decisions, than comparable trials in blocks 2 + 3 (0%) due to post-reversal decisions (Figure S1). The average performance of each monkey is shown in Figure 1D. To illustrate performance on individual testing sessions, the data were smoothed by calculating a running average over five trials that stopped at the last four trials of a block to avoid inclusion of trials in different blocks within a given average. Figures 1E and 1F show monkeys’ performances in two example sessions.
Affiliation: Department of Experimental Psychology, University of Oxford, OX1 3UD, Oxford, UK; Department of Psychology, The University of Hong Kong, Pokfulam Road, Hong Kong. Electronic address: firstname.lastname@example.org.