Stimulus-specific recruitment of human amygdala neurons predicts episodic memory encoding success

Abstract

Controlling whether an experience is encoded into long-term memory and thus later remembered is a crucial aspect of memory. Here we examined single-neuron activity in the human brain while participants formed memories for novel visual stimuli and later retrieved them with confidence ratings. Category-selective amygdala neurons exhibited elevated firing during encoding of later remembered items relative to later forgotten items. This effect was predictive of the episodic aspect of the memory, was restricted to the preferred category of each cell, emerged earlier and was stronger in the amygdala compared to the hippocampus, and did not depend on stimulus valence and arousal. Successful memory formation was accompanied by enhanced spike-field coherence between the activity of amygdala category cells and hippocampal field potentials. These findings demonstrate that stimulus-specific recruitment of the amygdala predicts memory formation and suggest category cells in the right amygdala as a target for interventions to treat disorders affecting episodic memory in humans. The study shows that stimulus-specific neurons in the human amygdala determine which experiences become lasting memory, revealing a mechanism that predicts episodic memory formation and may guide future treatments for memory disorders.