The amygdala's contribution to memory--a study on two patients with Urbach-Wiethe disease

The consequences of primary amygdaloid damage on memory performance are described in terms of neuropsychological, CT, MRI and PET results of two patients, a brother and a sister. Both had circumscribed, bilaterally symmetrical damage confined to the amygdaloid region, while the hippocampal formation and other brain structures were intact. PET-imaging furthermore revealed an overall decrease in glucose metabolism which was particularly apparent at the cingular and thalamic levels. Although neither patient was amnesic, both showed memory impairments in selective tests. In one patient these impairments were more pronounced and they were accompanied by marked affective-emotional fluctuations. Our results suggest that the amygdaloid region is a bottle-neck structure that confers an affective flavour to memories, thereby enhancing the probability of their long term storage.