Differential response patterns in the striatum and orbitofrontal cortex to financial reward in humans: a parametric functional magnetic resonance imaging study

Abstract

Responses to monetary reward in humans have been assessed in a number of recent functional imaging studies, and it is clear that the neuronal substrates of financial reinforcement overlap extensively with regions responding to primary reinforcers, such as food. Money has the practical advantage of being an objectively quantifiable reinforcer. In this study, we exploit this advantage using a parametric functional magnetic resonance imaging design to look at the patterns of responding to systematically varying reward values. Twelve healthy volunteers were scanned during performance of a rewarded target detection task, in which the reward value varied between task blocks. We observed three distinct patterns of responding in different regions. Amygdala, striatum, and dopaminergic midbrain responded to the presence of rewards, regardless of value. In contrast, premotor cortex showed a linear increase in response with increasing reward value. Finally, medial and lateral foci of orbitofrontal cortex responded nonlinearly, such that response was enhanced for the lowest and highest reward values relative to the midrange. These results suggest functional distinction in response patterns within a distributed reward system.

Figures

Fig. 1.

Blood oxygenation level-dependent (BOLD) responses in the striatum (A), midbrain (B), and amygdala (C) that showed an all-or-nothing response to reward. The mean adjusted response (no units) of ventral striatum to different reward values is shown inD, demonstrating the all-or-nothing response pattern. BOLD responses are thresholded at p < 0.001 uncorrected, but regional responses survive Bonferroni correction when the small volume procedure (Worsley et al., 1996) is used.

Fig. 2.

BOLD responses in the premotor cortex (A) that showed linear increase in response to increasing reward. The mean adjusted response (no units) of premotor cortex to different reward values is shown in B, demonstrating the linear response pattern. BOLD responses are thresholded at p < 0.001 uncorrected.

Fig. 3.

BOLD responses in the medial (BA 10;A) and lateral (BA 47; B) OFC that showed a U-shaped response to reward value. The mean adjusted responses (no units) of the two OFC foci to different reward values are shown inC and D, demonstrating the response pattern corresponding to an orthogonalized second-order polynomial expansion. BOLD responses are thresholded at p < 0.001 uncorrected, but regional responses survive Bonferroni correction when the small volume procedure (Worsley et al., 1996) is used.