Changes in brain connections occur very early in Alzheimer’s disease

Although much is known about brain alterations in symptomatic Alzheimer’s disease (AD), less is known about brain network changes early in the disease process. In a study published in Psychiatric Research: Neuroimaging last year, researchers found that the left parietal region, an area of ​​the brain that is also affected in symptomatic AD, becomes exceptionally prominent in the brain connections of people with preclinical AD.

There are two main reasons for our lack of knowledge about brain changes in early AD: firstly, because it is difficult to accurately predict who will have AD in the near future, and secondly, because Time-consuming investigative methods were often used. In a recent study conducted at the University of Tsukuba, researchers used a relatively quick method to study changes in the brain networks of a specific population at very high risk for AD.

The research team recruited elderly people who did not yet have dementia but who carried the apolipoprotein E4 gene, which increases the risk of AD and the accumulation of beta-amyloid (the main protein that accumulates in the brain of patients with AD). The researchers used a technique called positron emission tomography to identify amyloid buildup – which they believed to be a sign of early AD – in each person’s brain, and studied changes in the brain network throughout the brain. using magnetic resonance imaging. Both imaging methods are clinically advantageous because they are relatively common and quick to perform. The researchers then examined whether there was a relationship between amyloid accumulation and a range of brain network parameters.

Although we looked at many different possible relationships, we only found one that was significant. When there was more beta-amyloid accumulation, the left parietal region had greater intermediate centrality, which is a measure of a region’s influence on information transfer.”

Professor Tetsuaki Arai, lead author of the study

This result indicates that, in people with preclinical AD, the left parietal region becomes more prominent in the brain network. Notably, however, the authors found no relationship between amyloid accumulation and any other AD-related brain measure.

“Together, these results suggest that changes in the brain network occur very early in AD, before the development of large-scale brain structural and cognitive changes,” says lead author Professor Miho Ota. “In the future, these alterations could be used to diagnose very early AD.”

In addition to possible diagnostic use, these results may be useful in selecting subjects for clinical drug trials and in evaluating the effectiveness of treatments. This is important because many treatments aim to prevent Alzheimer’s disease in people who have not yet developed symptoms, and it can be difficult to identify these people.

This research was supported by an unrestricted research grant provided by Itoen, Tokyo, Japan.

Source:

Journal reference:

Ota, M. et al. (2022) Structural correlations of the brain network with amyloid load in older adults at risk for Alzheimer’s disease. Research in psychiatry: Neuroimaging. doi.org/10.1016/j.pscychresns.2021.111415.

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