Hippocampal and anterior cingulate cortex volumes in amnestic and non-amnestic mild cognitive impairment.

摘要

Mild Cognitive Impairment (MCI) is a syndrome thought to fall between cognitively normal aging and dementia. Although much research has investigated the structural neuroimaging correlates of amnestic MCI, little research has been done on the imaging correlates of non-amnestic MCI. Even less research has examined the anterior cingulate cortex (ACC), a region important in executive functions (EFs), in these patients. This study attempted to address this gap by examining hippocampal and ACC volumes among amnestic and non-amnestic MCI patients and cognitively normal controls. Those with amnestic MCI were expected to have smaller hippocampal volumes than controls and those with non-amnestic MCI, while those with non-amnestic MCI were expected to have smaller ACC volumes than controls or those with amnestic MCI. Fifty-seven participants, 21 cognitively normal controls, 20 with amnestic MCI, and 16 with non-amnestic MCI, were recruited. Contrary to hypotheses, mixed-model analyses of variance revealed no significant differences among the diagnostic groups in ACC or hippocampal volumes. These results suggest that the ACC is not involved in MCI or that it is affected only in later disease stages. The executive dysfunction seen in some cases of non-amnestic MCI may be due to atrophy in other brain regions associated with EF or may be due to white matter changes in these regions. However, the study's small, highly educated sample and the possibility that amnestic MCI patients also exhibited executive dysfunction may also have impacted results. Future research should longitudinally examine MCI patients with and without executive dysfunction to determine the role of the ACC and other brain regions involved in EF and should also investigate the correlation between neuropsychological test scores and volumes in these brain regions.