Ability to integrate diverse forms of information in current thought, or wo
rking memory, is essential for human reasoning and problem solving. We used
functional imaging to identify brain regions preferentially involved in ma
intaining integrated versus unintegrated information in working memory. For
equal amounts of verbal and spatial information, activation of prefrontal
cortex was greater for maintaining integrated rather than unintegrated repr
esentations. Posterior brain regions showed the opposite pattern. These res
ults demonstrate frontal-lobe specialization in maintaining working-memory
representations that integrate verbal and spatial information. The role of
prefrontal cortex in integrating multiple forms of information in working m
emory may underlie its unique contribution to high-level cognition that dem
ands flexible mental representations.