Cortical asymmetries in normal, mild cognitive impairment, and Alzheimer's disease.

There are functional and structural neocortical hemispheric asymmetries in people with normal cognition. These asymmetries may be altered in patients with Alzheimer's disease (AD) because there is a loss of neuronal connectivity in the heteromodal cortex. The purpose of this study is to test the hypothesis that individuals with amnestic mild cognitive impairment (aMCI), mild AD, and moderate to severe AD have progressive reductions in thickness asymmetries of the heteromodal neocortex. Right-handed elderly volunteers including normal cognition (NC), aMCI, and AD underwent 3-D volume imaging for cortical thickness. Although the cortical asymmetry pattern observed in normal cognition brains was generally maintained in aMCI and AD, there was a progressive decrease in the degree of asymmetry, especially in the inferior parietal lobule. A reduction of neocortical asymmetries may be a characteristic sign that occurs in patients with AD. Future studies are needed to evaluate whether this loss is specific to AD and if measurements of asymmetry can be used as diagnostic markers and for monitoring disease progression.