Have you ever found yourself stuck in a loop—repeating an action or thought without understanding why? While this experience is relatively common in daily life, it can also be exaggerated in neurological and psychiatric disorders such as autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD). Shedding light on the brain’s internal decision-making mechanisms, a groundbreaking study by Prof. Xin Jin’s team reveals how our brains choose between repeating an action and switching to a new one. This discovery offers promising new insights for treating a range of brain disorders and deepens our understanding of decision making in the brain.
Two Brain Circuits Drive Behavioral Flexibility
Our daily lives are full of micro-decisions—like deciding whether or not to keep scrolling on our phones, or to stop and take a lunch break. Though these choices seem mundane, behind them lies a sophisticated system of behavioral control in the brain. At the core of this system are two complementary neural circuits identified by Prof. Jin’s team: a repetition circuit, and a switching circuit. The repetition circuit, which connects the motor cortex to the dorsolateral striatum (M1-DLS), helps maintain habits and behavioral stability. Whereas, the switching circuit, which runs from the prefrontal cortex to the dorsomedial striatum (PrL-DMS), enables us to break routines and adapt to changing circumstances.
Intriguingly, researchers found that these circuits don’t function in isolation. In fact, the switching circuit can actively suppress the repetition circuit. This one-way inhibitory relationship allows the brain to override habitual behavior when flexibility is needed—forming the neural basis for adaptive decision-making.
A Mechanism for Autism and OCD
With disorders like ASD and OCD, repetitive behaviors and rigid thinking can interfere with daily functioning and social interaction. To investigate the relationship between adaptive decision-making and neurodivergent disorders, Prof. Jin’s team developed a model comparing switching mechanism alterations on a specific gene region for three subject groups: a control group, a Shank3 KO group, and a third group where a DMS intervention was performed on the Shank3 altered region. The results were striking: when the switching circuit was altered, it amplified repetitive behaviors and the mice displayed representative autism-like traits such as excessive self-grooming and repetitive actions.
The team traced the issue to a divergence in the PrL-DMS pathway, which is responsible for facilitating behavioral transitions. Remarkably, when researchers used molecular techniques to restore expression of the key Shank3 gene in the DMS region, the mice showed significant behavioral changes, away from repetitive expression. This provides compelling evidence that targeted neuromodulation or gene therapy could help alleviate repetitive, stereotyped behaviors in human patients.
Broader Implications for Neuroscience and AI
Beyond its clinical implications, this study deepens our understanding of the brain’s internal “behavioral switching system” and could inform future treatments for both motor and psychiatric disorders. Moreover, the mechanisms uncovered by Prof. Jin’s team may inspire advances in artificial intelligence, particularly in enhancing reinforcement learning algorithms and creating more adaptive decision-making systems.
The study, titled “Complementary corticostriatal circuits orchestrate action repetition and switching”, was published in the interdisciplinary journal Science Advances.
Journal Reference:
Zhang, B., Geddes, C.E., & Jin, X*. (2025). Complementary corticostriatal circuits orchestrate action repetition and switching. Science Advances, 11(21), eadt0854.
>> To read the article in Chinese at the School of Life Sciences, East China Normal University, click here.