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bioRxiv · 10.1101/725648

Hippocampal-amygdala interactions mediate uncertainty-dependent resistance to extinction following fear conditioning

Morris, J. S.·Windels, F.·Sah, P.
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Abstract

The partial reinforcement extinction effect (PREE) is a paradoxical learning phenomenon in which omission of reinforcement during acquisition results in more persistent conditioned responding in extinction. Here, we report a significant PREE with an inverted-U, entropy-like distribution against reinforcement probability following tone foot shock fear conditioning in rats, which was associated with increased neural activity in hippocampus and amygdala as indexed by p-ERK and c-fos immunolabelling. In vivo electrophysiological recordings of local field potentials (LFPs) showed that 50% reinforcement was associated with increases in the frequency and power of tone-evoked theta oscillations in both the subiculum region of hippocampus and in basolateral amygdala (BLA) during both acquisition (Day 1) and extinction (Day 2) sessions. Tone-evoked LFPs in 50% reinforced animals also showed increases in coherence and bidirectional Granger Causality between hippocampus and amygdala. The results support a Bayesian interpretation of the PREE, in which the phenomenon is driven by increases in the entropy or uncertainty of stimulus contingencies, and indicate a crucial role for hippocampus in mediating this uncertainty-dependent effect.

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Morris, J. S., Windels, F., Sah, P.. 2019-08-05. Hippocampal-amygdala interactions mediate uncertainty-dependent resistance to extinction following fear conditioning. https://doi.org/10.1101/725648

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