Abstract
Decision making often requires weighing costs and benefits of different options that vary in terms of reward magnitude and uncertainty. Previous studies using pharmacological inactivations have shown that the basolateral amygdala (BLA) to nucleus accumbens (NAc) pathway promotes choice towards larger/riskier rewards. Neural activity in BLA and NAc show distinct, phasic changes in firing prior to choice and following action outcomes, yet, how these temporally-discrete patterns of activity within BLA-NAc circuitry influence choice is unclear. We assessed how optogenetic silencing of BLA terminals in the NAc altered action selection during probabilistic decision making. Rats received intra-BLA infusions of viruses encoding the inhibitory opsin eArchT and were well-trained on a probabilistic discounting task, where they chose between smaller/certain rewards and larger rewards delivered in a probabilistic manner, with the odds of obtaining the larger reward changing over a session (50-12.5%). During testing, activity of BLA&cenveo_unknown_entity_wingdings_F0E0;NAc inputs were suppressed with 4-7 s pulses of light delivered via optic fibers into the NAc during discrete task events: prior to choice or after choice outcomes. Inhibition prior to choice reduced selection of the preferred option, suggesting that during deliberation, BLA-NAc activity biases choice towards preferred rewards. Inhibition during reward omissions increased risky choice during the low-probability block, indicating that activity after non-rewarded actions serves to modify subsequent choice. In contrast, silencing during rewarded outcomes did not reliably affect choice. These data demonstrate how patterns of activity in BLA-NAc circuitry convey different types of information that guide action selection in situations involving reward uncertainty.
Significance Statement Amygdala projections to the nucleus accumbens form a neural circuit that has been implicated in guiding risk-related decision making, and dysfunction in this circuitry is thought to underlie aberrant decision making observed a variety of psychiatric illnesses. The present study used temporally-discrete optogenetic inhibition to identify how activity in amygdala inputs to the accumbens, during different phases of the decision process, promotes optimal decision making. These findings provide novel insight into the mechanisms through which these circuits contribute to normal and abnormal decisions involving reward uncertainty.
Footnotes
The authors declare no competing financial interests.
This work was supported by grants from the Canadian Institutes of Health Research (MOP 133579).
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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