A UC Riverside-led team mapped a pathway linking the cortex, brainstem and spinal cord that helps control voluntary hand and arm movements. The study, published in the Proceedings of the National Academy of Sciences, shows signals travel not only directly from cortex to spinal cord but also through relay centers in the brainstem and the topmost spinal segments.
The researchers used fMRI to measure activity during controlled hand tasks in mice and humans. In mice, animals were trained to press a small lever with their forepaw while researchers recorded brain and brainstem activity. Human volunteers squeezed a device with varying force inside the scanner.
Scans revealed two regions of the medulla that were consistently active and strongly connected with sensorimotor parts of the cortex. The same regions appeared in both species, and the study shows that cervical spinal segments C3 and C4 act as a relay between the brainstem and the lower spinal cord that activates hand muscles. The findings point to a multi-stage pathway and suggest new targets for rehabilitation after stroke.
Difficult words
- cortex — outer layer of the brain for thinking and movement
- brainstem — part of the brain connecting to the spinal cord
- spinal cord — bundle of nerves inside the spine controlling movement
- medulla — lower part of the brainstem with vital control
- relay — a place or neuron that passes signals on
- sensorimotor — relating to both sensory and movement functions
- cervical — relating to the neck or upper spine area
- rehabilitation — treatment and exercises to recover lost abilities
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could knowing this multi-stage pathway help people recover movement after a stroke?
- Why do you think the researchers studied both mice and human volunteers?
- What kinds of rehabilitation exercises or therapies might use information about brainstem and cervical relays?
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