Neuronal activity in the human amygdala and hippocampus enhances emotional memory encoding

Abstract

SummaryEmotional events are often easier to recall, and comprise our most valuable memories. Here, as subjects performed a memory task in which they recalled emotional stimuli more readily than neutral stimuli, we used direct brain recording and stimulation in the hippocampus and amygdala to identify how the brain prioritizes emotional information for memory encoding. High-frequency activity (HFA), a correlate of local neuronal spiking, increased in both hippocampus and amygdala when subjects successfully encoded emotionally arousing stimuli. Direct electrical stimulation applied to these regions during encoding decreased HFA and selectively impaired retrieval for emotional stimuli. Finally, depressed subjects’ memory was biased more by valence than arousal, and they exhibited a congruent increase in HFA as a function of valence. Our findings thus provide evidence that emotional stimuli up-regulate activity in the amygdala–hippocampus circuit to enhance memory for emotional information, and suggest that targeted modulation of this circuit alters emotional memory processes.