UBC Theses and Dissertations
Optogenetic dissection of temporal dynamics of amygdala-striatal interplay during risk/reward decision making Bercovici, Debra Ann
Assessing costs and benefits associated with different options that vary in terms of reward magnitude and uncertainty is an adaptive behaviour which allows us to select an optimal course of action. Previous studies using reversible pharmacological inactivations have shown that the basolateral amygdala (BLA) to nucleus accumbens (NAc) pathway plays a key role in promoting choice towards larger, riskier rewards. Neural activity in the BLA and NAc show distinct, phasic changes in firing prior to action initiation and following action outcomes. Yet, how temporally precise patterns of activity within BLA-NAc circuitry influence choice behaviour is unclear. We assessed how optogenetic silencing of BLA projection terminals in the NAc altered action selection during probabilistic decision making. Rats that received intra-BLA infusions of an AAV encoding for the inhibitory opsin eArchT were well-trained on a probabilistic discounting task, where they chose between a smaller/certain reward and a larger/riskier reward, with the probability of obtaining the larger reward changing from 50% to 12.5% across two separate blocks of trials. During testing, discrete 4-7 second pulses of light were delivered via fiber optic ferrules into the NAc to suppress activity within BLA terminals during specific task events; during the period prior to choice or during the outcome immediately following a choice. Silencing activity of BLA inputs to the NAc prior to choice reduced selection of the more preferred option, suggesting that at this time, activity within this pathway biases choice towards more preferred rewards. Silencing during reward omissions increased risky choice during the low-probability block, indicating that activity in this circuit after non-rewarded actions serves to modify subsequent choice behaviour. In contrast, silencing during rewarded outcomes did not reliably affect choice behaviour. Collectively these data demonstrate how patterns of activity in BLA-NAc circuitry convey different types of information that guide optimal action-selection in situations involving reward uncertainty.
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