Memory accuracy for pairing faces with objects and scenes dropped sharply after young adulthood, with middle-aged and older adults scoring similarly rather than declining steadily. Brain activity patterns that helped younger adults remember accurately were linked, in older adults, to more mix-up errors crossing between entirely different categories of items, such as mistaking a scene for an object.

New brain-imaging research suggests aging brains may be blending memories together instead of simply forgetting them. A study published in Cerebral Cortex scanned brains of adults aged 18 to 74 as they learned pairs of faces with objects and faces with scenes, rested, and then tried to recall correct pairings. Researchers tracked activity patterns in the hippocampus at three points: during learning, rest, and recall.

Younger adults showed clean patterns where brain activity overlap predicted accuracy. But among older adults, that overlap predicted cross-category mistakes, like linking a face to a scene when it had been paired with an object. Their brains were retrieving too broadly rather than not at all.

Researchers analyzed data from 61 participants after excluding some for excessive head movement. The final group included 17 younger adults (ages 18 to 30), 21 middle-aged adults (ages 50 to 60), and 23 older adults (ages 61 to 74).