Reward Learning and Dopamine Release in Adults with 22q11DS

Abstract

Background

22q11.2 deletion syndrome (22q11DS) is a genetic disorder caused by a microdeletion on chromosome 22q11.2 and associated with an increased risk for psychosis. A dysfunctional motivational reward system is thought to be one of the salient features in psychosis caused by abnormal dopamine functioning. It is unknown whether patients with 22q11DS have a dysfunctional reward system.

Methods

This study aims to investigate reward learning in 22q11DS. The study included 10 adults with 22q11DS (age: 33.1 years, 60% female) and 10 age-gender-matched healthy controls (HC, age: 39.7 years, 60% female). A single infusion 18F-fallypride PET scan was acquired during which all subjects performed a version of the learning phase of the Probabilistic Stimulus Selection Task for reward learning (RL), modified to deliver social feedback.

Results

IQ-scores were significantly lower in the 22q11DS group (P < .001) compared to HC. The 22q11DS group both earned significantly less money (P < .05) and performed worse during the RL-task (P < .05) than HC. However, the learning curve for the RL-task was the same for both groups. IQ-scores were a significant positive predictor for earnings (P < .05) and performance (P < .05), but not for the learning curve.

Conclusions

These preliminary results indicate that people with 22q11DS are capable of learning at the same speed as HC, however they are less susceptible for reward than HC because their overall performance during RL is worse than HC. This lower reward sensitivity could be a result of haplo-insufficiency of COMT in 22q11DS and consequently abnormal prefrontal dopamine functioning.

Disclosure of interest

The authors have not supplied their declaration of competing interest.