Predictability Modulates Human Brain Response to Reward

TLDR

Certain stimuli such as food and drugs robustly activate reward regions. We investigate whether the predictability of sequential delivery of fruit juice and water modulates activity in human reward regions. Using fMRI, we measured activity in the nucleus accumbens and medial orbitofrontal cortex during delivery of the stimuli. Activity in reward regions was greatest when the stimuli were unpredictable, and preference for juice or water correlated with sensorimotor cortex activity rather than reward region activity, indicating that predictability modulates reward response while subjective preference is dissociated.

Abstract

Certain classes of stimuli, such as food and drugs, are highly effective in activating reward regions. We show in humans that activity in these regions can be modulated by the predictability of the sequenced delivery of two mildly pleasurable stimuli, orally delivered fruit juice and water. Using functional magnetic resonance imaging, the activity for rewarding stimuli in both the nucleus accumbens and medial orbitofrontal cortex was greatest when the stimuli were unpredictable. Moreover, the subjects' stated preference for either juice or water was not directly correlated with activity in reward regions but instead was correlated with activity in sensorimotor cortex. For pleasurable stimuli, these findings suggest that predictability modulates the response of human reward regions, and subjective preference can be dissociated from this response.