Elsevier

Biological Psychiatry

Volume 62, Issue 12, 15 December 2007, Pages 1388-1395
Biological Psychiatry

Original Article
A Functional Magnetic Resonance Imaging Study of Amygdala Responses to Human Faces in Aging and Mild Alzheimer’s Disease

https://doi.org/10.1016/j.biopsych.2006.11.013Get rights and content

Background

Neuropsychiatric symptoms are very common even in mild stages of Alzheimer’s disease (AD). The amygdala exhibits very early pathology in AD, but amygdala function in mild AD has received relatively little attention. The current study investigates functional alterations in the amygdala in aging and mild AD, and their relationships with neuropsychiatric symptoms.

Methods

Functional magnetic resonance imaging (fMRI) was used to examine and compare amygdala responses in 12 young and elderly controls and in 12 mild AD patients during viewing of neutral and emotional human facial expressions.

Results

Amygdala responses in the young and elderly did not significantly differ from each other. However, the AD group had significantly greater amygdala responses to both neutral and emotional faces relative to elderly controls. This group effect was maintained when amygdala volume, sex and age were included as covariates in the analysis. Furthermore, amygdala activity correlated with the severity of irritability and agitation symptoms in AD.

Conclusions

The amygdala in patients with mild AD is excessively responsive to human faces relative to elderly controls. These amygdala functional alterations may represent a physiologic marker for certain neuropsychiatric manifestations of AD.

Section snippets

Subjects

Thirty-six right-handed subjects were participants in the study: 12 healthy young adults (M = 24.2, SD = 2.0), 12 healthy elderly adults (M = 71.3, SD = 6.3), and 12 patients with probable mild Alzheimer’s disease (AD) (age: M = 71.8 years, SD = 9.6). There were 8 males, 4 females in each group. Healthy young subjects were recruited from the community. Healthy elderly subjects that were cognitively and affectively intact (see Supplemental Data) were recruited via the community or from an

Demographics

Table 1 presents these results. AD subjects performed significantly worse than the healthy elderly (t(22) = −5.89, p < .0001) and young (t(22) = −6.34, p < .0001) on the Mini Mental State Examination (MMSE), but there was no significant difference in MMSE scores between the young and elderly.

Postscan Ratings

No significant between the groups differences were present for successful recognition of the faces, but there was a trend for poorer performance in the AD group (vs. Elderly: (t(21) = −1.65, p < .11; vs.

Discussion

We demonstrate that mild AD is associated with alterations in amygdala responses to human faces with greater responses to both novel emotional and familiar neutral expressions compared with the healthy elderly. The amygdala results were regionally specific as the effects in the calcarine cortex were not significant. Yet, the calcarine cortex pattern was generally similar, possibly due to milder AD pathology in this region relative to the amygdala (Braak and Braak 1995, Cronin-Golomb et al 1991

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