The Relation between Amygdala Atrophy and Other Selected Brain Structures and Emotional Agnosia in Alzheimer Disease
Abstract
The amygdala and other structures of the limbic system are responsible for the analysis of signals carrying an emotional charge. The affection of the limbic system by a neurodegenerative process may cause a change in emotional perception or even emotional agnosia.
The article evaluates the relation between in vivo measured volumes of the amygdala, hippocampus, anterior cingular cortex, temporal lobe pole and emotional agnosia in patients with Alzheimer's disease as compared with the control population. Material and method: 26 patients with Alzheimer's disease and 17 members of the control group were subject to a magnetic resonance exam and a neuropsychological exam including an emotion recognition test using facial expression.
Magnetic resonance volumetry was used to measure the amy-gdala, hippocampus, anterior cingular cortex and temporal pole volumes. Results: All regional volume values obtained by the measurement and the results of neuropsychological tests were significantly worse in patients with AD as compared with the control group.
Comparison of regional volumes with the results of the emotion recognition test showed significant corre-lation between: left amygdala volume and the capacity to recognise joy (r = 0.54, p < 0.01) and sadness (r = 0.49, p < 0.05), right amygdala volume and the capacity to recognise fear (r = 0.34, p < 0.05) and sadness (r = 0.56, p < 0.01), the volume of both hippocampi and the capacity to recognise anger (r = 0.55 / right, and r = 0.58 / left, p < 0.01). Conclusion: The relation observed between a lower amygdala volume and a reduced capacity to recognise some emotions in patients with AD corroborates the hypothesis that emotional agnosia in AD patients is linked with atrophy of the amygdala and other limbic system structures.