The sooner the better: clinical and neural correlates of impulsive choice in Tourette disorder

Abstract

Reward sensitivity has been suggested as one of the central pathophysiological mechanisms in Tourette disorder. However, the subjective valuation of a reward by introduction of delay has received little attention in Tourette disorder, even though it has been suggested as a trans-diagnostic feature of numerous neuropsychiatric disorders. We aimed to assess delay discounting in Tourette disorder and to identify its brain functional correlates. We evaluated delayed discounting and its brain functional correlates in a large group of 54 Tourette disorder patients and 31 healthy controls using a data-driven approach. We identified a subgroup of 29 patients with steeper reward discounting, characterised by a higher burden of impulse-control disorders and a higher level of general impulsivity compared to patients with normal behavioural performance or to controls. Reward discounting was underpinned by resting-state activity of a network comprising the orbito-frontal, cingulate, pre-supplementary motor area, temporal and insular cortices, as well as ventral striatum and hippocampus. Within this network, (i) lower connectivity of pre-supplementary motor area with ventral striatum predicted a higher impulsivity and a steeper reward discounting and (ii) a greater connectivity of pre-supplementary motor area with anterior insular cortex predicted steeper reward discounting and more severe tics. Overall, our results highlight the heterogeneity of the delayed reward processing in Tourette disorder, with steeper reward discounting being a marker of burden in impulsivity and impulse control disorders, and the pre-supplementary motor area being a hub region for the delay discounting, impulsivity and tic severity.

Tourette syndrome research highlights from 2021

“…Another fMRI study focused on decisional impulsivity by using a delay-discounting task involving choosing between a small immediate reward or a larger delayed reward. 64 While they found no abnormal decisions in patients in comparison to a group of healthy controls, the authors identified a subgroup of patients with higher impulsivity. This group was also characterized by a higher burden of impulse-control disorders and a higher level of general impulsivity.…”

More widespread and rigid neuronal representation of reward expectation underlies impulsive choices

“…We interpret this across-subject result to reflect a lack of delayed discounting in response to risk cues in MI choosers and an inversion of risk estimation between LI and MI choosers. [81][82][83] Similar to reward, we see hemispheric differences between impulsivity groups, where MI choosers have greater encoding of risk in the left hemisphere, whereas LI choosers have greater encoding of risk in the right hemisphere. As our subject cohort has drug-resistant epilepsy, the electrode contacts are placed based solely on clinical considerations.…”

“…We interpret this across-subject result to reflect a lack of delayed discounting in response to risk cues in MI choosers and an inversion of risk estimation between LI and MI choosers. 81–83…”