Impact of amygdala functional connectivity on cognitive impairment in Alzheimer's disease.

The functional connectivity (FC) of the amygdala in Alzheimer's disease (AD) and its relationship to cognitive impairment is still not well established. Thus, we examined resting-state FC changes in the amygdala among 21 patients with AD dementia (ADD) and 34 individuals with amnestic mild cognitive impairment (aMCI), compared to 33 individuals with subjective cognitive impairment (SCI), to provide insights into the association between amygdala FC and cognitive decline in different clinical stages of Alzheimer's disease. We conducted seed-to-voxel FC analysis, focused on two cognitive functions, episodic memory, and face recognition, and examined the correlations between changes in FC of the amygdala and cognitive test scores. We demonstrated that the left amygdala exhibits progressive disruption in FC, especially with the frontal regions in aMCI and ADD. We further identified that this disrupted FC in the left amygdala showed significant positive correlations with cognitive test scores from the MCI stage onward. Our results indicate that FC changes in the left amygdala may serve as an early marker of AD and this FC pattern of amygdala influence detrimentally affects episodic memory and face recognition functions. These findings highlight that the amygdala may be a critical anatomical region for detecting the early stages of AD.