Age differences in behavior and PET activation reveal differences in interference resolution in verbal working memory

Older adults were tested on a verbal working memory task that used the item -recognition paradigm. On some trials of this task, response-conflict was c reated by presenting test-items that were familiar but were not members of a current set of items stored in memory. These items required a negative re sponse, but their familiarity biased subjects toward a positive response. Y ounger subjects show an interference effect on such trials, and this interf erence is accompanied by activation of a region on left lateral prefrontal cortex. However, there has been no evidence that the activation in this reg ion is causally related to the interference that the subjects exhibit. In t he present study, we demonstrate that older adults show more behavioral int erference than younger subjects on this task, and they also show no reliabl e activation at the same lateral prefrontal site. This leads to the conclus ion that this prefrontal site is functionally involved in mediating resolut ion among conflicting responses or among conflicting representations in wor king memory.