Researchers at Sweden’s Karolinska Institutet have discovered a brain circuit that triggers repetitive, compulsive actions in mice—even when they have access to natural rewards like food or social interaction. The findings, published in Science Advances, could deepen understanding of conditions such as obsessive-compulsive disorder and addiction.
Animals and humans alike can get locked into repetitive behaviors, but the underlying brain mechanisms have been unclear. The new study shows that a particular neural pathway can switch behavior into a kind of “repeat mode,” causing mice to carry out the same actions again and again, even after the reward has disappeared.
Optogenetics Uncovers a Repetitive-Behavior Circuit
The team examined a circuit stretching from the nucleus accumbens—a key part of the brain’s reward network—to a hypothalamic region linked to the lateral habenula, which processes negative experiences. Using optogenetics, a technique that allows researchers to control neurons with light, they activated this pathway and triggered a negative internal state in the mice. This, in turn, produced repetitive actions such as digging and sniffing, despite the presence of food and other rewards.
“We’ve pinpointed a brain pathway that can push behavior into a repetitive state. This gives us a clearer picture of how compulsive actions develop and may shed light on disorders like OCD and addiction,” says Konstantinos Meletis, a neuroscience professor at Karolinska Institutet, who led the work with assistant professor Daniela Calvigioni.
Repeated Circuit Activation Shifts Behavior Toward Compulsion
The researchers found that repeatedly activating the circuit connecting the nucleus accumbens and the hypothalamus gradually produced a negative internal state that made the mice favor repetitive actions over basic needs. When they blocked the downstream segment of the pathway—from the hypothalamus to the habenula—the compulsive behaviors stopped.
“This offers a fresh perspective on how the brain can elevate certain actions above others, even when they serve no purpose or provide no reward,” Meletis explains.
The findings come from a set of experiments in which the team used genetic techniques to label and follow specific neurons, tools to record brain activity, optogenetics to manipulate neural firing, and a range of behavioral tests. Together, these approaches allowed the researchers to connect compulsive-like behaviors to defined neural pathways.
Read the original article on: Medical Xpress
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