Age-related changes in regional cerebral blood flow during working memory for faces

Young and old adults underwent positron emission tomography during the perf ormance of a working memory task for faces (delayed match-to-sample), in wh ich the delay between the sample and choice faces was varied from 1 to 21 s . Reaction time was slower and accuracy lower in the old group, but not mar kedly so. Values of regional cerebral blood how (rCBF) were analyzed for su stained activity across delay conditions, as well as for changes as delay i ncreased, Many brain regions showed similar activity during these tasks in both young and old adults, including left anterior prefrontal carter, which had increased rCBF with delay, and ventral extrastriate cortex, which show ed decreased rCBF with delay. However, old adults had less activation overa ll and less modulation of rCBF across delay in right ventrolateral prefront al cortex than did the young adults. Old adults also showed greater rCBF ac tivation in left dorsolateral prefrontal cortex across all WM delays and in creased rCBF at short delays in left occipitoparietal cortex compared to yo ung adults. Activity in many of these regions was differentially related to performance in that it was associated with decreasing response times in th e young group and increasing response times in the older individuals. Thus despite the finding that performance on these memory tasks and associated a ctivity in a number of brain areas are relatively preserved in old adults, differences elsewhere in the brain suggest that different strategies or cog nitive processes are used by the elderly to maintain memory representations over short periods of time. (C) 1998 Academic Press.