Key Points Amygdala damage in humans reduces the memory-enhancing benefits of emotional arousal on consolidation processes and on attentional focusing during encoding. Memories for stressful and emotionally arousing events benefit from moderate doses of adrenaline and cortisol released acutely at the time of encoding. These effects have been linked to amygdala function in human and non-human animal studies. By contrast, chronic stress or high levels of acute stress hormones impair memory retrieval and hippocampal function, as exemplified by post-traumatic stress disorder. Encoding of emotionally arousing events recruits amygdala activity and elicits greater functional interactions between the amygdala and medial temporal lobe memory regions, which result in enhanced long-term memory. The interactions between the amygdala and medial temporal lobe memory regions extend to retrieval of remote memories, including those from the remote personal past. Emotional memories are retrieved with an accompanying sense of recollection rather than familiarity, an effect that depends on co-activation of the amygdala and hippocampus. The prefrontal cortex also has a role in the encoding and retrieval of emotional events and shows regional specialization for arousal and valence effects on memory. Across various species, the acquisition of conditioned fear depends on the integrity of the amygdala and its interactions with the thalamus and cortical structures. The extinction of fear behaviour requires a suppressive influence of the prefrontal cortex on amygdala function, and contextual cues processed by the hippocampus can reinstate extinguished fears. These cortical control mechanisms over emotional learning are thought to contribute to relapse of fears and phobias in anxiety disorders.
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