How Different Pathways in the Brain Work Together to Control Movement

A pioneering study by Professor Jin Xin's team has provided new insight into the brain's motor control system and its potential link to movement disorders such as Parkinson’s disease and obsessive-compulsive disorder. Published in the international journal eLife, the research uncovers an asymmetric, parallel connectivity pattern between the cortex and the basal ganglia.

From simple gestures to complex, coordinated actions, our brains orchestrate every movement we make. At the center of that coordination system are the brain’s cortical-basal ganglia circuits, which integrate signals from the cortex to guide behavior. However, identifying the precise mechanism through which the cortex regulates the distinct pathways of the basal ganglia has posed an ongoing challenge for researchers.

Using advanced viral tracing and optogenetics, a technique in which genes for light-sensitive proteins are introduced into neurons to precisely monitor and control their activity using light, Professor Jin and his team successfully revealed the asymmetric projections from cortical neurons to the two major pathways in the striatum—the direct (D1) and indirect (D2) pathways—within the basal ganglia.

While past studies have shown that cortical regions send excitatory signals to the striatum, where D1 and D2 SPNs are evenly distributed,  Professor Jin's team has uncovered that the projections from the cortex to these pathways utilize an intricate and parallel system of asymmetric communication to regulate movement, with the direct pathway being primarily driven by its corresponding cortical neurons, while the indirect pathway receives more balanced input that simultaneously influences both pathways.

These results provide concrete evidence that supports a revised framework for understanding how disruptions in the basal ganglia pathways can impact motor abnormalities, opening up new avenues for potential therapies and treatment strategies for disorders like Parkinson's, obsessive-compulsive disorder and autism spectrum disorder.