background Memory facilitation for emotional events has clear advantages in adaptive behaviour. An enhancement of emotional memory for negative information or reduction of memory for positive information has mainly been associated with depression.
aim To give an overview of two recent imaging studies investigating the neural underpinnings of emotional memory (bias) in healthy subjects.
method Event-related functional magnetic-resonance imaging was performed on healthy participants using on a full-factorial, within-subjects repeated-measures design to examine how mood (happy and sad) affects memory (recalled of forgotten) for valenced stimuli (positive, negative and neutral words). In the second study a similar experimental set-up was used to investigate the effect in genetic variation of noradrenergic transmission on neural underpinnings of emotional memory during sad mood-induction.
results In the first study, imaging results show amygdala and hippocampal engagement for global mood and subsequent recall effects, respectively. Mood-congruent memory effects were additionally characterised by increased activity during encoding of negative words in the orbitofrontal cortex (ofc) for congruent and inferior-frontal gyrus (ifg) for incongruent processing. The second study showed that the common deletion variant of the gene that codes for the alpha2b-adrenoceptor (adra2b) was related to enhanced activity in the amygdala and inferior frontal gyrus during successful emotional memory formation, but not retrieval.
conclusion In the healthy state amygdala and hippocampus next to prefrontal regions are involved in successful formation of emotional memories. Additionally, different pre-frontal processes facilitate the match between mood and stimulus valence at the time of learning of emotional information. Genetic variation in noradrenergic transmission affects the neural underpinnings of emotional memory formation independent of mood state.