Summary and Comment

In memory clinics and neurologists' offices, older adults frequent ask "Are my memory difficulties normal?" It is known all too well that changes in memory occur with age. Maguire and Frith set out to understand the neural correlates of these changes for remembering life events. They interviewed 12 younger subjects (average age, 32 years) and 12 older subjects (average age, 75 years) to identify memories of autobiographical events that were rich in detail and precision. They then asked the participants to retrieve these memories during functional MRI brain scans. As control tasks, participants also underwent scans while retrieving autobiographical facts unrelated to any particular event, memories of public events, and general knowledge. Compared with retrieval of these control tasks, retrieval of autobiographical events produced greater activation in the left hippocampus, medial frontal cortex, and retrosplenial cortex in both younger and older adults. Only older adults, however, showed additional activation of the right hippocampus during autobiographical event retrieval. This age-related difference in hippocampal activation was not present for the control tasks. The authors speculated that this extra activation in older adults may relate to their greater use of spatial processing in remembering autobiographical events compared with younger adults. Alternatively, they postulated that older adults may need the reserve capacity of the right hippocampus because the left hippocampus has undergone physiologic decline or because the left hippocampus has reached its capacity for memory traces due to the older adults' greater wealth of life experiences.

Comment: The finding of bilateral activation in older adults in situations where younger adults show unilateral activation fits in well with previous studies of memory, which have had similar results in frontal cortices for both encoding and retrieval of newly learned information (*Psychol Aging* 2002; 17:85). Future studies may help us to determine whether these differences represent changes in the mnemonic strategies of older adults, physiologic changes due to aging, or changes due to common pathologic conditions affecting older adults, such as small-vessel ischemic disease and the early pathology of Alzheimer's disease.

— AE Budson

in press, Journal Watch Neurology

Source: Maguire EA and Frith CD. Aging affects the engagement of the hippocampus during autobiographical memory retrieval. Brain 2003 Jul; 126: 1511-23.