Prefrontal cortex mediation of cognitive enhancement in rewarding motivational contexts

Jimura, Koji; Locke, Hannah; Braver, Todd S. · 2010 · OpenAlex-citations

DOI: 10.1073/pnas.1002007107

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Summary

This study investigates how motivational incentives, specifically monetary rewards, influence cognitive control and working memory performance, and how these effects vary based on individual personality traits. The authors address the gap in understanding the neural mechanisms and individual differences that optimize motivation-linked cognitive enhancement. Guided by the Dual Mechanisms of Control (DMC) framework, which distinguishes between proactive (sustained, anticipatory) and reactive (transient, stimulus-driven) control modes, the research tests whether rewarding contexts shift cognitive strategies toward proactive control in the lateral prefrontal cortex (lPFC). The researchers conducted an experiment with 31 participants who performed a demanding working memory task during functional magnetic resonance imaging (fMRI) scanning. The design included two motivational contexts: a rewarding context (R+) where monetary bonuses were contingent on performance, and a non-rewarding context (R-). Within the R+ context, trials varied in reward value (high, low, or none). The study utilized a mixed blocked/event-related fMRI design to dissociate sustained (block-wise) activation from transient (trial-by-trial) activation. Individual differences in trait reward sensitivity were assessed using a composite index derived from standard personality assessments. Behavioral results showed that reaction times were significantly faster in the R+ context compared to the R- context, particularly on non-rewarded trials. This contextual performance enhancement was positively correlated with participants' trait reward sensitivity. Neuroimaging data revealed that the R+ context induced a shift in right lPFC activation dynamics: sustained activation increased significantly, while late-trial transient activation decreased. This pattern indicates a shift from reactive to proactive control. Crucially, this neural shift was not driven by trial-by-trial reward fluctuations but was purely contextual. Highly reward-sensitive individuals exhibited the strongest increase in sustained lPFC activity and an additional early-trial transient boost, corresponding to enhanced anticipatory maintenance of task goals. The study concludes that the cognitive benefits of motivational incentives are mediated by a shift toward proactive control in the lPFC. Mediation analysis confirmed that the relationship between reward sensitivity and improved performance was statistically mediated by this specific pattern of neural activation (increased sustained and early transient activity, decreased late transient activity). The findings suggest that individuals high in reward sensitivity preferentially adopt a resource-demanding proactive strategy in rewarding contexts, which globally optimizes performance, including on trials that do not offer immediate reward. This provides evidence that motivational salience translates into optimal cognitive strategy through dynamic changes in prefrontal cortex activation.

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• executive function