Reward Sensitivity and Waiting Impulsivity: Shift towards Reward Valuation away from Action Control

02 Oct 2017

Background: Impulsivity and reward expectancy are commonly inter-related. Waiting impulsivity, measured using the rodent 5-Choice Serial Reaction Time (5-CSRT) task, predicts compulsive cocaine seeking and sign (or cue) tracking. Here we assess human waiting impulsivity using a novel translational task, the 4-CSRT, and the relationship with reward cues. Methods: Healthy volunteers (n=29) performed the monetary incentive delay task as a functional MRI study where subjects observe a cue predicting reward (cue) and wait to respond for high (£5), low (£1) or no reward. Waiting impulsivity was tested with the 4-CSRT. Results: For high reward prospects (£5 – no reward), greater waiting impulsivity on the 4-CSRT correlated with greater medial orbitofrontal cortex (OFC) and lower supplementary motor area (SMA) activity to cues. In response to high reward cues, greater waiting impulsivity was associated with greater subthalamic nucleus connectivity with OFC and greater subgenual cingulate connectivity with anterior insula but decreased connectivity with regions implicated in action selection and preparation. Conclusion: These findings highlight a shift towards regions implicated in reward valuation and a shift towards compulsivity away from higher level motor preparation and action selection and response. We highlight the role of reward sensitivity and impulsivity, mechanisms potentially linking human waiting impulsivity with incentive approach and compulsivity, theories highly relevant to disorders of addiction.