Abnormal resting-state functional connectivity of posterior cingulate cortex in amnestic type mild cognitive impairment.

Amnestic type mild cognitive impairment (aMCI) refers to a transitional stage between normal aging and Alzheimer's disease (AD). Whilst posterior cingulate cortex (PCC) is believed to have a key role in a default network and be involved in the pathophysiology of AD, few studies have investigated whole-brain functional connectivity of PCC during resting state, or investigated the relationship between abnormal functional connectivity and disturbance in cognitive function in aMCI patients. Resting-state functional connectivity analysis was used to examine the temporal correlation between PCC and whole-brain regions in 30 aMCI patients and 26 well-matched controls. Further analysis involved evaluation of possible relationships between functional connectivity measures and cognitive function. Regions of decreased functional connectivity were identified in aMCI patients, most notably in temporal cortex, whilst significantly increased functional connectivity was mainly in frontal cortex. In addition, functional connectivity of PCC and temporal cortex was associated with the performance of neuropsychological tests in aMCI patients. This would be consonant with the recruitment of compensatory mechanisms and the process of offset functional impairments appearing as neuropathologic develops, and resting-state connectivity disturbance of PCC-temporal cortex may be a central role in cognitive deficit in aMCI patients.