Adults With Alzheimer's Risk Factors Show Subtle Alterations in Brain Networks Despite Normal Cognition

A study in the Journal of Alzheimer's Disease explores how a known genetic risk factor for late-onset Alzheimer's disease (AD) impacts memory and brain function in cognitively intact older adults with a family history of the disorder, reports Medical Xpress . The researchers probed the gene apolipoprotein E (APOE), which has three allelic variants — e2, e3, and e4. Of these variants, previous studies demonstrated that adults with a single APOE e4 (+APOEe4) gene are more likely to develop AD. The new study applied functional magnetic resonance imaging to investigate whether carrying a +APOEe4 genotype changed brain activity during memory task performance in older adults who may be at risk of AD. "It turns out that the +APOEe4 variant . . . doesn't directly affect memory performance or brain activity in cognitively intact older adults," said McGill's Sheida Rabipour. "Rather, +APOEe4 seems to influence the brain regions and systems that older at-risk adults activate to support successfully remembering past events." Older adults with APOEe4 use different brain regions, such as the parietal cortex, to support successful memory encoding, while those who lack APOEe4 utilize traditional memory-related brain regions, like medial temporal lobes and prefrontal cortex, for the same process. The implication is that +APOEe4, when examined to the exclusion of family history, has a subtle effect on the correlation between brain activity and memory performance.