An examination of the effects of stimulus type, encoding task, and functional connectivity on the role of right prefrontal cortex in recognition memory

Right anterior prefrontal cortex and other brain areas are active during me mory retrieval but the role of prefrontal cortex and how it interacts with these other regions to mediate memory function remain unclear. To explore t hese issues we used positron emission tomography to examine the effects of stimulus material and encoding task on brain activity during visual recogni tion, assessing both task-related changes and functional connectivity. Word s and pictures of objects were encoded using perceptual and semantic strate gies, resulting in better memory for semantically encoded items. There was no significant effect of prior encoding strategy on brain activity during r ecognition. Right anterior prefrontal cortex was equally active during reco gnition of both types of stimuli irrespective of initial encoding strategy. Regions whose activity, was positively correlated with activity in right a nterior prefrontal cortex included widespread areas of prefrontal and infer ior temporal cortices bilaterally. Activity in this entire network of regio ns was negatively correlated with recognition accuracy of semantically enco ded items. These results suggest that initial encoding task has little impa ct on the set of brain regions that is active during subsequent recognition . Right anterior prefrontal cortex appears to be involved in retrieval mode , reflected in its equivalent activity across conditions differing in both stimulus type and encoding task, and also in retrieval effort, shown by the negative correlation between its functional connectivity and individual di fferences in recognition accuracy. (C) 2001 Academic Press.