Irvine, Calif., March 7, 2018 — As we get older, it’s not uncommon to experience “senior moments,” in which we forget where we parked our car or call our children by the wrong names. And we may wonder: Are these memory lapses a normal part of aging, or do they signal the early stages of a severe disorder such as Alzheimer’s disease? Currently, there’s no good way to tell.

University of California, Irvine-led researchers, however, have found that high-resolution functional magnetic resonance imaging of the brain can be used to show some of the underlying causes of differences in memory proficiency between older and younger adults.

The study, which appears today in the journal Neuron, involved 20 young adults (ages 18 to 31) and 20 cognitively healthy older adults (ages 64 to 89). The participants were asked to perform two kinds of tasks while undergoing fMRI scanning – an object memory task and a location memory task. Because fMRI looks at the dynamics of blood flow in the brain, investigators were able to determine which parts of the brain the subjects were using for each activity.
In the first task, participants viewed pictures of everyday objects and were then asked to distinguish them from new pictures. “Some of the images were identical to ones they’d seen before, some were brand-new and others were similar to ones they’d seen earlier – we may have changed the color or the size,” said Michael Yassa, director of UCI’s Center for the Neurobiology of Learning & Memory and the study’s senior author. “We call these tricky items the ‘lures.’ And we found that older adults struggle with them. They’re much more likely than younger adults to think they’ve seen those lures before.”

The second task was nearly the same but required subjects to determine whether the location of objects had been altered. Here, older adults fared quite a bit better than in the prior task.

“This suggests that not all memory changes equally with aging,” said lead author Zachariah Reagh, who participated in the study as a graduate student at UCI and is now a postdoctoral fellow at UC Davis. “Object memory is far more vulnerable than spatial, or location, memory – at least in the early stages.” Other research has shown that problems with spatial memory and navigation do manifest as individuals progress toward Alzheimer’s disease.

Importantly, by scanning the subjects’ brains while they underwent these tests, the scientists were able to establish a cerebral mechanism for that deficit in object memory.

They found that it was linked to a loss of signaling in a part of the brain called the anterolateral entorhinal cortex. This area is already known to mediate communication between the hippocampus, where information is first encoded, and the rest of the neocortex, which plays a role in long-term storage. It’s also an area severely affected in people with Alzheimer’s disease.

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