Impairment and compensation coexist in amnestic MCI default mode network.

Mild cognitive impairment (MCI) is the transitional, heterogeneous continuum from healthy elderly to Alzheimer's disease (AD). Previous studies have shown that brain functional activity in the default mode network (DMN) is impaired in AD patients. However, altering DMN activity patterns in MCI patients remains largely unclear. The present study utilized resting-state functional magnetic resonance imaging (fMRI) and an independent component analysis (ICA) approach to investigate DMN activity in 14 amnestic MCI (aMCI) patients and 14 healthy elderly. Compared to the aMCI patients, the healthy elderly exhibited increased functional activity in the DMN regions, including the bilateral precuneus/posterior cingulate cortex, right inferior parietal lobule, and left fusiform gyrus, as well as a trend towards increased right medial temporal lobe activity. The aMCI patients exhibited increased activity in the left prefrontal cortex, inferior parietal lobule, and middle temporal gyrus compared to the healthy elderly. Increased frontal-parietal activity may indicate compensatory processes in the aMCI patients. These findings suggest that abnormal DMN activity could be useful as an imaging-based biomarker for the diagnosis and monitoring of aMCI patients.

Qi Z ，Wu X ，Wang Z ，Zhang N ，Dong H ，Yao L ，Li K ... -  《-》

Functional connectivity of the fusiform gyrus during a face-matching task in subjects with mild cognitive impairment.

Bokde AL ，Lopez-Bayo P ，Meindl T ，Pechler S ，Born C ，Faltraco F ，Teipel SJ ，Möller HJ ，Hampel H ... -  《-》

Default-mode network activity distinguishes amnestic type mild cognitive impairment from healthy aging: a combined structural and resting-state functional MRI study.

Bai F ，Zhang Z ，Yu H ，Shi Y ，Yuan Y ，Zhu W ，Zhang X ，Qian Y ... -  《NEUROSCIENCE LETTERS》

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

Bai F ，Watson DR ，Yu H ，Shi Y ，Yuan Y ，Zhang Z ... -  《-》

Cognitive reserve modulates task-induced activations and deactivations in healthy elders, amnestic mild cognitive impairment and mild Alzheimer's disease.

Cognitive reserve (CR) reflects the capacity of the brain to endure neuropathology in order to minimize clinical manifestations. Previous studies showed that CR modulates the patterns of brain activity in both healthy and clinical populations. In the present study we sought to determine whether reorganizations of functional brain resources linked to CR could already be observed in amnestic mild cognitive impairment (a-MCI) and mild Alzheimer's disease (AD) patients when performing a task corresponding to an unaffected cognitive domain. We further investigated if activity in regions showing task-induced deactivations, usually identified as pertaining to the default-mode network (DMN), was also influenced by CR. Fifteen healthy elders, 15 a-MCI and 15 AD patients underwent functional magnetic resonance imaging (fMRI) during a speech comprehension task. Differences in the regression of slopes between CR proxies and blood-oxygen-level dependent (BOLD) signals across clinical groups were investigated for activation and deactivation areas. Correlations between significant fMRI results and a language comprehension test were also computed. Among a-MCI and AD we observed positive correlations between CR measures and BOLD signals in task-induced activation areas directly processing speech, as well as greater deactivations in regions of the DMN. These relationships were inverted in healthy elders. We found no evidence that these results were mediated by gray matter volumes. Increased activity in left frontal areas and decreased activity in the anterior cingulate were related to better language comprehension in clinical evaluations. The present findings provide evidence that the neurofunctional reorganizations related to CR among a-MCI and AD patients can be seen even when considering a preserved cognitive domain, being independent of gray matter atrophy. Areas showing both task-induced activations and deactivations are modulated by CR in an opposite manner when considering healthy elders versus patients. Brain reorganizations facilitated by CR may reflect behavioral compensatory mechanisms.

Bosch B ，Bartrés-Faz D ，Rami L ，Arenaza-Urquijo EM ，Fernández-Espejo D ，Junqué C ，Solé-Padullés C ，Sánchez-Valle R ，Bargalló N ，Falcón C ，Molinuevo JL ... -  《-》