By Pesach Benson • September 23, 2026
Jerusalem, 23 September, 2026 (TPS-IL) — A brain system that normally helps keep behavior flexible may be turned against itself by cocaine, Israeli scientists have found. The discovery could help explain how compulsive and repetitive behaviors emerge and points researchers toward a specific brain mechanism that can be manipulated to interrupt them.
The study, led by PhD students Ben Jerry Gonzales and Itay Shalom under the supervision of Prof. Ami Citri of the Hebrew University of Jerusalem’s Edmond and Lily Safra Center for Brain Sciences and Institute of Life Sciences, identifies a balance between two neural pathways that appears to determine whether behavior remains flexible or becomes locked into repetition.
“Cocaine does not appear to create an entirely new behavioral program,” Gonzales, a co-first author, said. “It takes control of a circuit the brain already uses for natural actions and pushes behavior toward persistent repetition.”
The study, published in the peer-reviewed journal Current Biology, traced the effect to a brain circuit involved in selecting movements, particularly those involving the mouth and tongue.
The study focused on the striatum, a brain region involved in selecting actions from moment to moment. Disruptions in this process have been associated with repetitive and rigid behaviors in conditions including Tourette syndrome, Parkinson’s disease and drug-induced movement disorders.
To examine these changes, the team developed STEREO, a deep-learning system that uses artificial intelligence to identify and track natural behaviors directly from video. The technology allowed the researchers to monitor an animal’s full behavioral repertoire rather than manually recording individual actions.
“We wanted to capture behavior as an observer actually sees it: grooming, licking, exploring, but this was impossible to score manually,” Shalom, a co-first author, said. “STEREO allowed us to watch how the animals’ entire behavioral repertoire progressively narrowed until one type of action came to dominate.”
After repeated cocaine exposure, the animals’ varied and exploratory behavior gradually narrowed toward repetitive actions. They increasingly spent time licking the floor and walls of their enclosure, behaviors rarely observed without cocaine.
Tracing the Brain Circuit
The researchers traced this change to the ventrolateral striatum, or VLS, a region involved particularly in movements of the mouth and tongue. The VLS contains two major neural pathways, known as the direct and indirect pathways, which have opposing effects on action selection.
Activating the indirect pathway immediately interrupted the cocaine-induced repetitive behavior and caused the animals to shift toward alternative actions. When the stimulation stopped, the repetitive behavior rapidly returned.
Suppressing the same pathway had the opposite effect, making it harder for the animals to switch behaviors and producing longer bouts of repetitive action.
The direct pathway showed the opposite pattern. Reducing its activity weakened cocaine-induced repetitive behavior, while activating it in the absence of cocaine was sufficient to produce rigid, repetitive actions resembling those seen after drug exposure.
The findings suggest that cocaine-induced behavioral rigidity results from an imbalance between two opposing pathways within a normal action-selection system. Rather than simply identifying a brain region associated with repetitive behavior, the study demonstrates that manipulating the balance between these pathways can alter the behavior itself.
The researchers said the findings provide a specific brain mechanism for further investigation as a potential target for restoring behavioral flexibility. The STEREO system also Offers a new way to study repetitive behavior in greater detail.
In the longer term, the findings raise the possibility of treatments aimed at restoring the brain’s ability to switch between behaviors rather than simply suppressing repetitive actions. However, the researchers cautioned that whether the same circuit mechanism can be targeted safely and effectively in humans remains to be determined.
