Abstract
Emotional material tends to be better retrieved in memory than neutral material. This emotional enhancement of memory may be related to the attentional effects of the amygdala's response to emotional stimuli. Because early neuropathological changes in Alzheimer's disease involve the amygdala and the hippocampus, it has been suggested that this effect is impaired in patients. However inconsistent results have been reported. The goal of our study was to evaluate the effects of emotion on picture recognition in patients affected by Alzheimer's disease, and to explore the link between this effect and the degree of amygdalar and hippocampal atrophy. Mild Alzheimer's disease patients (n = 15) and control participants (n = 20) performed an Old/New recognition task using pictures of negative, neutral, and positive emotional valence. Automated segmentation of their high-resolution T1 MRI scans was performed in order to obtain amygdalar and hippocampal volumes. Correlation analyses were then performed between volumetric data, memory, and the emotional effect on memory. An effect of emotion on memory was found for control participants (with positive items being better recognized than neutral and negative ones), with no correlation between this effect and medial temporal volumes, and a significant correlation between overall recognition scores and hippocampal volumes. Conversely, no emotional effect on memory was found across the group of patients; however, significant correlations were found between the loss of this effect and amygdalar and hippocampal volumes. These results tend to confirm a link between the loss of emotional effect on memory and neuropathological change in medial temporal structures during the course of Alzheimer's disease.