Corticospinal transmission in human subjects

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The corticospinal pathway is the major route from the brain to the spinal cord for the control of voluntary movement in people. Little is known about how transmission through this pathway might alter with activity. It is known that, elsewhere in the brain, connections between nerve cells can be made stronger or weaker by specific patterns of activity and it is thought that such changes underlie learning and memory. We propose that similar changes might happen in the spinal cord at the connection between the nerve cells which carry signals from the brain and the nerve cells which carry the signals out to the muscle. This project will demonstrate that the connections in the pathway from the brain to the muscle can be strengthened or weakened in a controlled way by imposed patterns of activity. In addition, we know that after voluntary contractions, there are dramatic changes in the way signals in this pathway are transmitted to muscles. After brief strong voluntary contractions, muscle responses are immediately reduced. After longer contractions in which the muscles become fatigued, the reduction is followed by an increase in responses which can last many minutes. Thus, this project will also study changes in the pathway from the brain to the muscle after natural activity. The effects of changes induced by artificial or natural activity on the control of voluntary movement will also be investigated. Understanding how activity drives changes in the pathway that controls voluntary movement is important for all situations that involve learning motor tasks. These include normal development and learning of motor skills, as well as rehabilitation after all kinds of nerve or muscle injury. It is also important in understanding motor changes that occur when activity is altered by disorders like spinal cord injury or stroke. Improved understanding of the processes occuring should allow improvement in rehabilitation therapies.