Brain connectivity changes in progression towards dementia

Alzheimer’s disease is the most common form of dementia, affecting approximately 10% of individuals aged above 65. Most scientists agree that early detection and prevention of the disease would be more effective than trying to cure dementia. In this study, we found that increased connectivity in a specific network of the brain was associated with a progression towards dementia.

The main aim of the study was to identify longitudinal changes in brain networks at rest in patients with mild cognitive impairment (MCI; stage between the expected cognitive decline of normal aging and the more serious decline of dementia, characterized by problems with memory, language, thinking or judgment) and to relate these functional changes to clinical progression (i.e., progression towards dementia or not).

Functional connectivity was assessed in a group of 44 patients with MCI over 1.2 years (three sessions using functional MRI) and cognitive testing were performed over 3 years (i.e., five sessions). We tracked the evolution of functional connectivity between and inside brain networks to assess changes in brain connectivity and compared it with a group of clinically normal older adults. Difference in functional connectivity was observed longitudinally and for the final recording session, where MCI patients who progressed towards dementia during their cognitive follow-up had significantly higher connectivity compared to MCI without dementia, specifically within the default mode network (a network associated with self-directed thoughts or introspection, as shown in the figure). In addition, the rate of changes in connectivity was significantly associated with the rate of cognitive decline.

Further research using multimodal brain imaging would be useful to appraise the distinct predictive role of brain connectivity compared to other biomarkers in Alzheimer’s Disease.

Malotaux V, Dricot L, Quenon L, et al. Default-mode network connectivity changes during the progression towards Alzheimer's dementia: A longitudinal functional MRI study. Brain Connect 2022; doi: 10.1089/brain.2022.0008. Link to the paper here

Default-mode network (represented in red)

Default mode network (represented in red)

Published on October 18, 2022