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UC San Diego researchers were among the scientists to generate a map of connectivity from a part of the brain responsible for many motor and behavioral functions, which may grant greater insight on treating brain abnormalities, it was announced Monday.

The cluster of neurons known as the basal ganglia is a central hub for regulating those functions. But when signaling in the basal ganglia is weakened or broken, debilitating movement and psychiatric disorders can emerge, including Parkinson’s disease, Tourette’s syndrome, attention deficit hyperactivity disorder and obsessive-compulsive disorder.

In Monday’s issue of the journal Neuron, researchers at UCSD, Columbia University’s Zuckerman Institute and their colleagues charted a map of brain connectivity from a part of the basal ganglia, an area known as the substantia nigra pars reticulata, or SNr.

The findings offer a blueprint of the area’s architecture that reveal new details and a “surprising” level of influence connected to the basal ganglia, the researchers said.

The research spearheaded by Lauren McElvain — an assistant project scientist at UCSD — and carried out in the neurophysics laboratory of Professor David Kleinfeld at UCSD, and the laboratory of Zuckerman Institute Principal Investigator Rui Costa, establish an understanding of the position of the basal ganglia in the hierarchy of the body’s motor system. According to the researchers, the newly identified pathways emerging from the connectivity map could potentially open additional avenues for intervention of Parkinson’s disease and other disorders tied to the basal ganglia.

“With the detailed circuit map in hand, we can now plan studies to identify the specific information conveyed by each pathway, how this information impacts downstream neurons to control movement and how dysfunction in each output pathway leads to the diverse symptoms of basal ganglia diseases,” McElvain said.

With support from the National Institutes of Health’s Brain Research through Advancing Innovative Neurotechnologies Initiative, the researchers developed the blueprint working in mice.

Previous work emphasized the basal ganglia architecture is dominated by a closed-loop with output projections connecting back to input structures. The new study reveals the SNr broadcasts even to lower levels of the motor and behavior system. This includes a large set of brainstem regions with direct connections to the spinal cord and motor nuclei that control muscles via a small number of intervening connections.

“The new findings led by Dr. McElvain offer an important lesson in motor control,” said Kleinfeld, a professor in the division of biological sciences and division of physical sciences. “The brain does not control movement though a hierarchy of commands, like the `neural networks’ of self- driving cars, but through a scheme of middle management that directs motor output while informing the executive planners.”

According to the researchers, the SNr neurons projecting to the low levels of the motor system have branched axons that simultaneously project back up to the brain regions responsible for higher-order control and learning. In this way, the connectivity of SNr neurons links operations across high and low levels of the brain.

–City News Service

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