β-amyloid (Aβ) and cerebrovascular disease burden have divergent effects on longitudinal default mode network and executive control network functional connectivity (FC) changes in amnestic mild cognitive impairment (MCI) and subcortical vascular MCI, according to a study published online in Neurology.

Joanna Su Xian Chong, Ph.D., from the Duke-National University of Singapore Medical School, and colleagues examined 30 patients with amnestic MCI and 55 with subcortical vascular MCI with baseline Pittsburgh Compound B (PiB)-positron emission tomography scans and longitudinal magnetic resonance imaging (MRI) scans. Participants were followed clinically for up to four years with annual MRI.

The researchers observed a correlation for Aβ burden with longitudinal default mode network FC declines and an association for cerebrovascular burden with longitudinal executive control network FC changes. The patients were categorized as PiB+ and PiB−; PiB+ patients showed longitudinal declines in default mode network FC, while longitudinal executive control network FC increases were seen for patients with subcortical vascular MCI. This pattern was also seen in direct comparisons between the groups without mixed pathology: amnestic MCI PiB+ patients showed steeper longitudinal declines in default mode network FC, while steeper longitudinal executive control network FC increases were seen for subcortical vascular MCI PiB− patients.

"Our results suggest that longitudinal changes in default mode network and executive control network FC reflect the underlying pathology and may be used to track early changes in Alzheimer disease and cerebrovascular disease," the authors write.

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