Researchers have identified a potential new biomarker for Alzheimer’s disease, according to a new study published in the journal NeuroImage: Clinical. The biomarker in question is functional connectivity, or the way in which different regions of the brain communicate with one another. While previous studies had shown that there is often a decrease in local connectivity in the brains of Alzheimer’s patients, the current study goes further in examining connectivity between different regions of the brain, and how this connectivity is affected by the presence of a genetic risk factor for Alzheimer’s, namely the APOE ε4 allele.
The researchers used data from the Alzheimer’s Disease Neuroimaging Initiative, focusing on participants who had been assessed for symptom severity, and underwent both T1-weighted and resting-state functional MRI at phases 2 and 3 of the study. Participants were divided into two groups based on whether or not they were APOE ε4 carriers, and participants with ε2 alleles were excluded. Ultimately, the researchers were left with a group of 235 participants (120 APOE ε4 carriers and 115 non-carriers) for analysis.
To measure functional connectivity, the researchers used a technique that involved mapping individual participants’ cortical functional networks, which were matched with an atlas of 116 cortical regions of interest (ROIs). Connections between different ROIs were classified as being either within-network or between-network, depending on whether they connected two ROIs in the same or different networks, respectively.
The researchers found that APOE ε4 carriers had significantly lower connectivity compared to APOE ε4 non-carriers, both within and between networks. They also found that lower within-network connectivity was associated with more severe symptoms, as measured by cognitive impairment scores. The researchers suggest that this connectivity measure could provide a new biomarker for Alzheimer’s disease, which is not only more informative than previous biomarkers, but could also be used to identify people at risk of Alzheimer’s before the onset of symptoms.
