The neural system that bridges reward and cognition in humans: An fMRI study

TLDR

The study builds on the idea that the medial frontal pole monitors reward value during cognition and that deactivation of limbic regions may gate emotional signals to enhance performance. The authors aimed to test whether motivational and cognitive processes are linked by a specific neural system that maximizes efficiency. Six healthy adults performed n‑back working‑memory tasks with varying monetary rewards while undergoing fMRI to map brain activation. Results revealed that higher cognitive load and reward both increased activity in dorsolateral and lateral frontopolar prefrontal regions (especially in the 3‑back task) and in the medial frontal pole, while simultaneously decreasing activation in ventral and subgenual prefrontal areas, indicating a balance between cortical engagement and limbic inhibition during demanding cognitive processing.

Abstract

We test the hypothesis that motivational and cognitive processes are linked by a specific neural system to reach maximal efficiency. We studied six normal subjects performing a working memory paradigm ( n- back tasks) associated with different levels of monetary reward during an fMRI session. The study showed specific brain activation in relation with changes in both the cognitive loading and the reward associated with task performance. First, the working memory tasks activated a network including the dorsolateral prefrontal cortex [Brodmann area (BA) 9/46] and, in addition, in the lateral frontopolar areas (BA 10), but only in the more demanding condition (3-back task). This result suggests that lateral prefrontal areas are organized in a caudo-rostral continuum in relation with the increase in executive requirement. Second, reward induces an increased activation in the areas already activated by working memory processing and in a supplementary region, the medial frontal pole (BA 10), regardless of the level of cognitive processing. It is postulated that the latter region plays a specific role in monitoring the reward value of ongoing cognitive processes. Third, we detected areas where the signal decreases (ventral-BA 11/47 and subgenual prefrontal cortices) in relation with both the increase of cognitive demand and the reward. The deactivation may represent an emotional gating aimed at inhibiting adverse emotional signals to maximize the level of performance. Taken together, these results suggest a balance between increasing activity in cortical cognitive areas and decreasing activity in the limbic and paralimbic structures during ongoing higher cognitive processing.