Time-dependent neural arbitration between cue associative and episodic fear memories

Nature Communications volume  15, Article number: 8706 (2024 ) Cite this article

After traumatic events, simple cue-threat associative memories strengthen while episodic memories become incoherent. However, how the brain prioritises cue associations over episodic coding of traumatic events remains unclear. Here, we developed an original episodic threat conditioning paradigm in which participants concurrently form two memory representations: cue associations and episodic cue sequence. We discovered that these two distinct memories compete for physiological fear expression, reorganising overnight from an overgeneralised cue-based to a precise sequence-based expression. With multivariate fMRI, we track inter-area communication of the memory representations to reveal that a rebalancing between hippocampal- and prefrontal control of the fear regulatory circuit governs this memory maturation. Critically, this overnight re-organisation is altered with heightened trait anxiety. Together, we show the brain prioritises generalisable associative memories under recent traumatic stress but resorts to selective episodic memories 24 h later. Time-dependent memory competition may provide a unifying account for memory dysfunctions in post-traumatic stress disorders.

Traumatic events impact human memories in multiple ways1,2. On one hand, threatening events strengthen associative learning to link aversive outcomes with predictive cues in the environment3,4. For example, emotionally neutral cues—such as a bicycle—acquire a threatening value after they are experienced in a traumatic vehicle accident. The cues can then evoke fear-like responses in anticipation of the associated threat, which become prolonged and exaggerated in patients suffering from post-traumatic stress disorder (PTSD)5,6.

Leave a Comment