Role of the amygdala in emotional memory. A case study

We report on the case of a 28-year old female (DP) with bilateral amygdalohippocampal abnormalities in MR imaging caused by suspected limbic encephalitis. DP developed a complex-partial epilepsy and secondary generalized seizures. T1-weighted MRI sequences two weeks after the onset of symptoms showed bilateral signal hyperintensities in both hippocampus and amygdala but no otherwise focal brain damage. Tc-99m-ECD SPECT demonstrated decreased tracer uptake in the right temporal region. DP suffered from complete retrograde amnesia for at least 3-4 years and gradually diminished memory for the last 10-15 years from earlier life periods only general events could be recalled which showed a prominent lack of specific details. Cueing provided by her family lead to a vague feeling of familiarity for childhood-events, whereas more recent-even highly affect-laden-episodes were not recognised at all. Besides comprehensive neuropsychological testing we administered 2 experimental tasks developed to examine emotional memory performance. DP is particularly impaired in recognition of emotionally charged stimuli, despite rating these items as highly emotional. Our data are consistent with previous studies of patients with bilateral amygdala-damage but additionally indicate that the blockade of the memory-enhancing effect of arousal due to lesions of the amygdala is evident even in patients with severe amnesia. The present results corroborate the hypothesis that the AC plays a critical role in paradigms where arousal enhances memory by affecting organization of memory.