Altered default-mode network activation in mild cognitive impairment compared with healthy aging

Rapidly increasing aging of the world's population is causing a heightened prevalence of Alzheimer's disease (AD) and mild cognitive impairment (MCI). The global burden, caused by this, is tremendous. In order to slow down the progression of the disease and preserve quality of life as much as possible, early identification of subjects at risk is indispensable within this framework. In the present study, we combined independent component analysis and statistical parametric analysis to identify and compare the default-mode network (DMN) in healthy elderly and patients with MCI, with a special interest for hippocampal and lateral temporal involvement. Functional results indicated reduced cortical activation in the DMN for MCI patients, compared with age- and education-matched healthy elderly controls, mainly in the retrosplenial region/posterior cingulate cortex, left hippocampus, and bilateral inferior and middle frontal areas. Increased activation for patients was observed in the medial prefrontal and bilateral middle temporal/angular cortex. Lateral temporal involvement in the DMN was in both the elderly control samples, and the patient group detected and suggested a slightly increased activation, more right than left, in middle temporal areas in the MCI patients, compared with healthy elderly. Results are discussed with reference to the existing literature on early pathological changes in MCI and AD and subsequent compensation mechanisms in resting state and memory circuits.