Context-Dependent Human Extinction Memory Is Mediated by a Ventromedial Prefrontal and Hippocampal Network

TLDR

In fear extinction, an animal learns that a conditioned stimulus no longer predicts a noxious stimulus, creating a new CS–noUCS memory trace that competes with the initial fear memory, and recall of extinction memory is facilitated by contextual stimuli present during extinction training. The study aimed to demonstrate that CS‑evoked activation of the ventromedial prefrontal cortex and hippocampus is context dependent after extinction. The results show that CS‑evoked VMPFC–hippocampal activity and its positive correlation are context dependent, supporting a network that mediates context‑dependent recall of extinction memory.

Abstract

In fear extinction, an animal learns that a conditioned stimulus (CS) no longer predicts a noxious stimulus [unconditioned stimulus (UCS)] to which it had previously been associated, leading to inhibition of the conditioned response (CR). Extinction creates a new CS–noUCS memory trace, competing with the initial fear (CS–UCS) memory. Recall of extinction memory and, hence, CR inhibition at later CS encounters is facilitated by contextual stimuli present during extinction training. In line with theoretical predictions derived from animal studies, we show that, after extinction, a CS-evoked engagement of human ventromedial prefrontal cortex (VMPFC) and hippocampus is context dependent, being expressed in an extinction, but not a conditioning, context. Likewise, a positive correlation between VMPFC and hippocampal activity is extinction context dependent. Thus, a VMPFC–hippocampal network provides for context-dependent recall of human extinction memory, consistent with a view that hippocampus confers context dependence on VMPFC.