Researchers have mapped contrasting brain responses to rewards in attention deficit hyperactivity disorder and autism spectrum disorder, revealing that the same deep brain structures are involved but activate in opposite ways. The analysis, published in Molecular Psychiatry, pooled 29 neuroimaging studies and included 468 people with ADHD, 424 with ASD and 1,027 control participants, all scanned using functional magnetic resonance imaging while receiving monetary or social rewards.
Reward processing is a fundamental mechanism that guides learning and motivation. When a reward is received, brain networks evaluate its value and influence future behaviour. Atypical responses within these systems are a feature of several neurodevelopmental conditions.
Biological patterns differ in ADHD and ASD
In ADHD, the subcortical regions responsible for emotions and reward evaluation show abnormally high activity during reward delivery, particularly in the amygdala and putamen. This heightened response is associated with a strong pull towards immediate gratification and impulsive choices.
By contrast, individuals with ASD exhibit unusually low activity in the same subcortical areas when rewards are delivered, suggesting a reduced internal reinforcement from rewards, including social cues.
Beyond these deep brain structures, the two conditions diverge in the cortex. Those with ADHD show reduced activity in the prefrontal cortex and other regions involved in impulse control and decision making, while individuals with ASD display heightened activity in medial prefrontal regions that attribute subjective value to specific interests.
To better understand these differences, the researchers conducted a second analysis using an independent database of healthy brain scans to probe how the altered amygdala and putamen connect with the rest of the brain. They found that ADHD-related hyperactive regions were heavily linked to circuits governing motivation and emotional responses, whereas ASD-related hypoactive regions were more connected to social and cognitive networks.
Using a large database called Neurosynth to map the abnormal brain patterns onto cognitive functions, the team found that the ADHD hyperactive areas aligned with terms tied to intense emotions, while the ADHD hypoactive regions corresponded to attention and executive control. In ASD, hyperactive zones matched social and value-related processing, and hypoactive zones related to novelty and basic affective processing.
The researchers then examined how these maps align with known distributions of chemical messengers in the brain. They looked at dopaminergic and serotonergic receptors through positron emission tomography data. Dopamine is linked to immediate reward seeking, while serotonin helps regulate longer-term goals and impulse control.
They observed that ADHD’s hyperactive regions overlapped with areas densely populated by both dopamine and serotonin receptors, offering a neurochemical framework for impulsive behaviour driven by a highly responsive reward system coupled with weaker prefrontal control. In ASD, the overactive value-processing regions lay in areas with low serotonin transporter density, while underactive subcortical regions mapped to zones rich in dopamine and serotonin receptors, suggesting a general desensitisation to rewards.
Despite these illuminating patterns, the study notes several limitations. The meta-analysis pooled a moderate number of studies and grouped different reward types together, potentially masking distinctions between social and monetary rewards. There were not enough ASD-specific studies to separate reward types statistically, and the connectivity analyses relied on scans from healthy individuals rather than patients.
The authors conclude that directly mapping these networks in patient populations will be a crucial next step, and that future work should consider separating reward types to refine brain signatures further. The study was led by Chunhong Zhu, Mercy Chepngetich Bore, Xueke Wang, Ting Xu and Tingyong Feng of Southwest University in China.
