Dissociation Of Working Memory from Decision Making within the Human Prefrontal Cortex

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Abstract
We tested the hypothesis that cognitive functions related to working memory (assessed with delay tasks) are distinct from those related to decision making (assessed with a gambling task), and that working memory and decision making depend in part on separate anatomical substrates. Normal controls (n= 21), subjects with lesions in the ventromedial (VM) (n= 9) or dorsolateral/high mesial (DL/M) prefrontal cortices (n= 10), performed on (1) modified delay tasks that assess working memory and (2) a gambling task designed to measure decision making. VM subjects with more anterior lesions (n= 4) performed defectively on the gambling but not the delay task. VM subjects with more posterior lesions (n= 5) were impaired on both tasks.RightDL/M subjects were impaired on the delay task but not the gambling task.LeftDL/M subjects were not impaired on either task. The findings reveal a cognitive and anatomic double dissociation between deficits in decision making (anterior VM) and working memory (right DL/M). This presents the first direct evidence of such effects in humans using the lesion method and underscores the special importance of the VM prefrontal region in decision making, independent of a direct role in working memory.