A classification task involving marking images of items as “new,” “old,” or “similar” to a prior set of images helps explain how and why older people have difficulty forming new memories and distinguishing similar objects from one another, Michael Yassa and his team at Johns Hopkins’ Krieger School of Arts and Sciences found.

Using MRI, Yassa observed how the brains of college students are more likely to show hippocampal activity in response to images of new items that are similar to prior items, but with subtle differences. Subjects in the 60-80 age group had more of a tendency to mark similar objects as “old” rather than “similar” or “new”.

“Pictures had to be very distinct from each other for an older person’s hippocampus to correctly classify them as new. The more similar the pictures were, the more the older person’s hippocampus struggled to do this. A young person’s hippocampus, on the other hand, treated all of these similar pictures as new,” Yassa explains.

Ref.: Michael Yassa et al., Age-related memory deficits linked to circuit-specific disruptions in the hippocampus, Proceedings of the National Academy of Sciences, April 15, 2011.