Behavioral/Systems/Cognitive The Locus Ceruleus Is Involved in the Successful Retrieval of Emotional Memories in Humans

Emotionalmemories arebetter remembered thanneutral ones. Theamygdala is involved in this enhancementnotonlybymodulating the hippocampal activity, but possibly also by modulating central arousal. Using functional magnetic resonance imaging, we analyzed the retrieval of neutral faces encoded in emotional or neutral contexts. Thepupillary sizemeasuredduring encodingwasused as amodulator of brain responses during retrieval. The interaction between emotion and memory showed significant responses in a set of areas, including the amygdala and parahippocampal gyrus. These areas responded significantlymore for correctly remembered faces encoded in an emotional, comparedwith neutral, context. The same interaction conducted on responsesmodulated by the pupillary size revealed an area of the dorsal tegmentumof the ponto-mesencephalic region, consistent with the locus ceruleus.Moreover, a psychophysiological interaction showed that amygdalar responses were more tightly related to those of the locus ceruleus when remembering faces that had been encoded in an emotional, rather than neutral, context. These findings suggest that the restoration of a central arousal similar to encoding takes part in the successful retrieval of neutral events learned in an emotional context. Key words: emotion; memory; locus ceruleus; amygdala; pupillary size; functional magnetic resonance imagin