Researchers used high-powered functional magnetic resonance imaging (fMRI) to map changes in the brain neurocircuitry of 27 people who lost, and then regained, the use of their hands after suffering brain damage because of cerebral palsy, multiple sclerosis or stroke.
Brain images were taken as the study participants opened and closed their hands every three seconds.
In healthy people, about 80 percent of the neurological activity controlling hand motion is in the primary motor cortex, an area of the brain at the crown of the head.
In this group of people, nerve firing in the primary motor cortex was reduced on average to about 60 percent.
However, other areas of the brain took over processing hand motion, including neurological networks located next to the motor cortex and in the nearby "helper" motor cortex, an area that normally handles more complicated actions, such as swallowing.
In contrast to healthy people, the people with brain damage had increased neurological activity in the primary motor cortex located in the brain hemisphere on the same side of the body as the hand being moved, instead of in the brain hemisphere on the opposite side of the body.
The study found that, in some of the people with brain damage, the cerebellum also helped control hand motion. The cerebellum, also called the "little brain" is located at the base of the brain and is typically involved in coordinating movement, getting instructions from the motor cortex and feedback from the limbs.
The study was presented April 1 at the American Academy of Neurology's annual meeting in Honolulu.
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