Newswise - When Your Brain Talks, Your Muscles Don't Always Listen

Newswise — Have your neurons been shouting at your muscles again? It happens, you know.

As we grow older, neurons--the nerve cells that deliver commands from our brains--have to “speak” more loudly to get the attention of our muscles to move, according to University of Delaware researcher Christopher Knight, an assistant professor in UD's College of Health Sciences.

“As a result of age-related changes in muscle and neurons, elderly people are often frustrated by poor control during precision tasks, and slowed physical responses contribute to more falls as people grow older,” Knight said.

Knight and co-author Gary Kamen, who directs the Exercise Neuroscience Laboratory at the University of Massachusetts, recently published the results of a study on motor-unit firing rates in the Journal of Applied Physiology, and Knight is now beginning a new project focusing on motor-control mechanisms in the elderly. Both studies are sponsored by the National Institutes of Health.

The ultimate goal of the research, Knight said, is to improve movement quality in older adults, as well as patients with disorders such as cerebral palsy or multiple sclerosis, or who are recovering from strokes.

Every move you make is made possible through a miraculous communications network involving the brain at the command center, the spinal cord, billions upon billions of nerve cells, and thousands of muscle fibers.

“Muscles are the driving force behind our movements,” Knight said. “Every time they get a command from the neurons, the muscle fibers contract. In the generation of muscular force, the smallest controllable unit consists of an individual neuron and the muscle fibers it stimulates. We believe that our research is very important to our understanding of motor-control mechanisms in general and impaired control in patient populations.”

Shedding light on the communication between neurons and muscles, and how it changes as we age, may lie right at our fingertips, according to Knight's research.

Using an experimental apparatus he and his students created in UD's Human Performance Lab, Knight has been examining muscular force on a very small scale in the index finger, specifically, the first dorsal interosseous muscle. Located between the index finger and the thumb, this muscle contains 120 “motor units”--in other words, 120 individual neurons, or nerve cells, and the muscle fibers they activate.

“It's a relatively simple muscle, so you get to see more of a one-to-one relationship between the activity of the neurons and the resulting muscular force,” Knight said....[MORE]