Abstract
The hippocampus plays a central role in the approach–avoidance conflict that is central to the genesis of anxiety. However, its exact functional contribution has yet to be identified. We designed a novel gambling task that generated approach–avoidance conflict while controlling for spatial processing. We fit subjects’ behavior using a model that quantified the subjective values of choice options, and recorded neural signals using functional magnetic resonance imaging (fMRI). Distinct functional signals were observed in anterior hippocampus, with inferior hippocampus selectively recruited when subjects rejected a gamble, to a degree that covaried with individual differences in anxiety. The superior anterior hippocampus, in contrast, uniquely demonstrated value signals that were potentiated in the context of approach–avoidance conflict. These results implicate the anterior hippocampus in behavioral avoidance and choice monitoring, in a manner relevant to understanding its role in anxiety. Our findings highlight interactions between subregions of the hippocampus as an important focus for future study.
Highlights
Approach–avoidance conflict arises when animals encounter probabilistic gains and losses within the same experience and are forced to balance the desire to seek reward with the impulse to avoid harm
Subjects faced many different combinations of colored backgrounds and numbers of activated tokens, and had to combine these 2 pieces of information to calculate the probability of an activated bomb (P(ActBomb)) on each trial. These gambles were further encountered in 2 experimental conditions The approach–avoidance (Ap/Av) condition (Fig. 1A, bottom left) invoked an approach–avoidance conflict, because increasing the number of tokens implied a greater magnitude of potential reward (+10 p/token) as well as a greater probability of a substantial loss
We examined hippocampal contributions to approach–avoidance conflict by developing a novel decision-making task that separated behavioral avoidance from the decision to gather more information
Summary
Approach–avoidance conflict arises when animals encounter probabilistic gains and losses within the same experience and are forced to balance the desire to seek reward with the impulse to avoid harm. Such conflict between approach and avoidance is thought to be central to the generation of anxiety, a state of high arousal and negative valence that is experienced in the absence of an immediate threat (Russell 1980; Davis and Shi 1999; Gray and McNaughton 2000; Calhoon and Tye 2015). Forward planning and information seeking may, to some extent, depend on shared neuronal mechanisms, it is unclear whether such hippocampal-dependent processes are more likely to be engaged in the context of approach–avoidance conflict (as suggested by Gray et al.)
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