Remembering One Year Later: Role of the Amygdala in Retrieving Consolidated Emotional Memories

Although there is general agreement that the amygdala plays an important role in the encoding of emotional memories, the role of this brain region during the retrieval of emotional memory is unclear. According to one view, the amygdala plays a role during encoding but not during retrieval of consolidated emotional memories. To investigate this issue, we used event-related fMRI to measure brain activity in female participants during the encoding and retrieval of emotional and neutral pictures. During encoding, participants were scanned while rating the emotional content of the pictures. One year later, the same participants were scanned again during a recognition task that included studied pictures mixed with new distractors. Consistent with the idea that emotion can enhance memory, recognition accuracy was better for emotional than for neutral pictures. The main finding of the retrieval fMRI data was that the left amygdala was more activated during successful retrieval (hits minus correct rejections) of emotional pictures than during successful retrieval of neutral pictures. Interestingly, this activation overlapped with an amygdalar activation that was identified during encoding using subsequent memory analyses (remembered minus forgotten). In other words, the same amygdalar region was associated with successful encoding as well as with successful retrieval of emotional memories. This is the first direct evidence that the amygdala is involved in emotional memory both during encoding and during retrieval.