DISSOCIATION OF WORKING-MEMORY FROM DECISION-MAKING WITHIN THE HUMAN PREFRONTAL CORTEX

We tested the hypothesis that cognitive functions related to working m emory (assessed with delay tasks) are distinct from those related to d ecision making (assessed with a gambling task), and that working memor y 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 memo ry and (2) a gambling task designed to measure decision making. VM sub jects with more anterior lesions (n = 4) performed defectively on the gambling but not the delay task. VM subjects with more posterior lesio ns (n = 5) were impaired on both tasks. Right DL/M subjects were impai red on the delay task but not the gambling task. Left DUM subjects wer e not impaired on either task. The findings reveal a cognitive and ana tomic double dissociation between deficits in decision making (anterio r VM) and working memory (right DL/M). This presents the first direct evidence of such effects in humans using the lesion method and undersc ores the special importance of the VM prefrontal region in decision ma king, independent of a direct role in working memory.