Dissociating Planning and Working Memory Processes Within The Human Lateral Frontal Cortex

ALBERT LEE; FACUNDO MANES; DANIEL BOR; TREVOR ROBBINS; ADRIÁN OWEN

New Orleans

Encuentro; Neuroscience Annual Meeting 2000; 2000

Society For Neuroscience

Neuroimaging studies and investigations in neurosurgical patients with frontal-lobe excisions have demonstrated that tests of cognitive planning and working memory recruit overlapping regions of the lateral frontal cortex. In part, this correspondence may reflect similarities in the requirements of the tasks employed; for example, many standard planning tasks, such as the Tower of London test, also make significant demands on aspects of working memory. In this PET study, we compared a number of novel tasks that were designed to emphasize either cognitive planning, working memory, or a combination of the two. As expected, both types of task activated widely overlapping regions within the dorsolateral and ventrolateral frontal cortices when compared to a matched visuomotor control condition. However, when the experimental tasks were compared directly, clear distinctions were observed. Specifically, increasing the planning load while minimizing working memory demands yielded greater blood flow changes in the mid-dorsolateral frontal cortex. In contrast, increasing the requirement to retrieve items from working memory yielded greater activation in regions of the ventrolateral frontal cortex. Corroborative data from neurosurgical patients with damage to the frontal cortex will be presented and the results discussed in terms of current models of lateral frontal-lobe organisation.