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

TLDR

The study tested whether working memory and decision making rely on distinct cognitive processes and anatomical substrates. Participants included 21 controls and 19 patients with ventromedial or dorsolateral/high mesial prefrontal lesions who completed delay‑task working‑memory tests and a gambling decision‑making task. Lesions in anterior ventromedial cortex impaired decision making but spared working memory, posterior ventromedial lesions impaired both, right dorsolateral/high mesial lesions impaired working memory only, and left dorsolateral/high mesial lesions had no deficits, demonstrating a double dissociation and highlighting the ventromedial region’s role in decision making independent of working memory.

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. Right DL/M subjects were impaired on the delay task but not the gambling task. Left DL/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.