Neuronal Signals in the Monkey Basolateral Amygdala during Reward Schedules

Abstract

The amygdala is critical for connecting emotional reactions with environmental events. We recorded neurons from the basolateral complex of two monkeys while they performed visually cued schedules of sequential color discrimination trials, with both valid and random cues. When the cues were valid, the visual cue, which was present throughout each trial, indicated how many trials remained to be successfully completed before a reward. Seventy-six percent of recorded neurons showed response selectivity, with the selectivity depending on some aspects of the current schedule. After a reward, when the monkeys knew that the upcoming cue would be valid, 88 of 246 (36%) neurons responded between schedules, seemingly anticipating the receiving information about the upcoming schedule length. When the cue appeared, 102 of 246 (41%) neurons became selective, at this point encoding information about whether the current trial was the only trial required or how many more trials are needed to obtain a reward. These cue-related responses had a median latency of 120 ms (just between the latencies in inferior temporal visual area TE and perirhinal cortex). When the monkey was releasing a touch bar to complete the trial correctly, 71 of 246 (29%) neurons responded, with responses in the rewarded trials being similar no matter which schedule was ending, thus being sensitive to the reward contingency. Finally, 39 of 246 (16%) neurons responded around the reward. We suggest that basolateral amygdala, by anticipating and then delineating the schedule and representing reward contingency, provide contextual information that is important for adjusting motivational level as a function of immediate behavior goals.