Organization of working memory within the human prefrontal cortex: a PET study of self-ordered object working memory

The prefrontal col tex plays a critical role in working memory, the active maintenance of information for brief periods of time for guiding future mot or and cognitive processes. Two competing models have emerged to account fo r the growing human and non-human primate literature examining the function al neuroanatomy of working memory. One theory holds that the lateral fronta l cortex plays a domain-specific role in working memory with the dorsolater al and ventrolateral cortical regions supporting working memory for spatial and non-spatial material, respectively. Alternatively, the lateral frontal cortex may play a process-specific role with the more dorsal regions becom ing recruited whenever active manipulation or monitoring of information in working memory becomes necessary. Many working memory tasks do not allow fo r direct tests of these competing models. The present study used a novel se lf-ordered working memory task and positron emission tomography to identify whether dorsal or ventral lateral cortical areas are recruited during a wo rking memory task that required extensive monitoring of non-spatial informa tion held within working memory. We observed increased blood flow in the ri ght dorsolateral. but not ventrolateral, prefrontal cortex. Increases in bl ood flow in the dorsolateral region correlated strongly with task performan ce. Thus, the results support the process-specific hypothesis. (C) 2000 Els evier Science Ltd. All rights reserved.