Temporal discounting in adolescents and adults with Tourette syndrome

Abstract

Tourette syndrome is a neurodevelopmental disorder associated with hyperactivity in dopaminergic networks. Dopaminergic hyperactivity in the basal ganglia has previously been linked to increased sensitivity to positive reinforcement and increases in choice impulsivity. In this study, we examine whether this extends to changes in temporal discounting, where impulsivity is operationalized as an increased preference for smaller-but-sooner over larger-but-later rewards. We assessed intertemporal choice in two studies including nineteen adolescents (age: mean[sd] = 14.21[±2.37], 13 male subjects) and twenty-five adult patients (age: mean[sd] = 29.88 [±9.03]; 19 male subjects) with Tourette syndrome and healthy age- and education matched controls. Computational modeling using exponential and hyperbolic discounting models via hierarchical Bayesian parameter estimation revealed reduced temporal discounting in adolescent patients, and no evidence for differences in adult patients. Results are discussed with respect to neural models of temporal discounting, dopaminergic alterations in Tourette syndrome and the developmental trajectory of temporal discounting. Specifically, adolescents might show attenuated discounting due to improved inhibitory functions that also affect choice impulsivity and/or the developmental trajectory of executive control functions. Future studies would benefit from a longitudinal approach to further elucidate the developmental trajectory of these effects.

Differences in Discounting Behavior and Brain Responses for Food and Money Reward

“…To address this concern, we conducted additional analyses after excluding food and monetary trials with payoffs occurring after 6 and 12 months. Although these supplementary analyses confirmed the results of previous studies ( Schüller et al, 2021 ) and our results obtained from the complete dataset, it remains uncertain whether participant behavior would have differed, had they been confronted with individually tailored food items and more realistic prices. Especially for highly delayed rewards, higher-priced food is more likely to be discounted than lower-priced food.…”

“…These findings underscore the importance of considering scaling of individual differences in time insensitivity/sensitivity to reliably capture superior features of discounting behavior with Bayesian modeling ( Ebert and Prelec, 2007 ). Schüller et al (2021) have chosen a comparable approach and found that discounting money over shorter delays (up to 6 months compared with 1 year in our study) is also better captured by exponential as compared with hyperbolic discounting, which supports the validity of our findings even though our task included exceptionally long delays (e.g., 6 and 12 months). Despite convincing results of our model comparison, the parameter recovery of the winning model was only successful for k , as a measure of impulsivity, but not s, a factor of time sensitivity.…”

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

“…Abnormal reward processing, in particular, greater reward sensitivity, has been suggested to be a behavioural marker of TD [ 1 ]. However, only two studies previously investigated delay discounting of reward in TD, using a task similar to that used in the present study, also showing steeper reward discounting, but only for large rewards and only for adolescents suffering from TD [ 9 , 10 ]. In addition, as one of the previous study, we reported no significant effect of ADHD or OCD co-morbidities [ 10 ].…”

“…However, only two studies previously investigated delay discounting of reward in TD, using a task similar to that used in the present study, also showing steeper reward discounting, but only for large rewards and only for adolescents suffering from TD [ 9 , 10 ]. In addition, as one of the previous study, we reported no significant effect of ADHD or OCD co-morbidities [ 10 ]. However, we found that connectivity between the right pre-SMA and the ventral striatum was related to both delay discounting and attentional impulsivity assessed with the BIS-11.…”

“…The first one was performed on a small sample of young persons with pure TD and no medication and showed a steeper delay discounting in TD patients in comparison to a control group only for rewards of large magnitude [ 9 ]. The second was carried out on both TD adolescents and adults using a computational approach and revealed temporal discounting only for adolescents’ patients in comparison to a matched control group which was not correlated to tics severity or co-morbidities [ 10 ]. Thus, it remains unclear whether abnormal reward processing in TD spreads beyond the reinforcement learning in adults with TD, if it is associated with specific clinical features and especially what are its functional brain correlates.…”