Reward modulation of prefrontal and visual association cortex during an incentive working memory task

Cognitive performance differs with motivation, but little direct evidence exists regarding the neural mechanisms of the influence of reward motivation on working memory (WM). We tested the effects of motivation on the top-down control in visual WM. Encoding relevant stimuli for maintenance, while suppressing inappropriate inputs is considered a core process in cognition. Prior functional magnetic resonance imaging (fMRI) results demonstrated that stimulus-specific visual association cortex serves as a marker of activation differences for task-relevant and task-irrelevant inputs, such that enhanced activity occurs when attention is directed to relevant stimuli and suppressed activity occurs when attention is directed away from irrelevant stimuli [Gazzaley, A., Cooney, J., McEvoy, K., Knight, R.T., and D'Esposito, M. J. Cogn. Neurosci. 17, 507-517]. We used fMRI to test whether differential WM performance, indexed by lowered response times on a delayed-recognition task, was associated with amplification of enhancement and suppression effects during stimulus encoding within visual association cortex. Our results indicate that enhancement and suppression are amplified for trials with the highest reward level relative to non-rewarded trials for a scene-selective cortical region. In a face-selective region, similar modulation of enhancement for the highest reward level relative to non-rewarded trials was found. Prefrontal cortex also showed enhanced activity during high reward trials. Overall these results reveal that reward motivation can play a pivotal role in driving performance through top-down signaling in frontal regions involved in WM, as well as visual association regions selective to processing the perceptual inputs of the items to be remembered.