Solving a Piece of the Paralysis Puzzle

Neuroscience research using lampreys holds promise for answering questions about human spinal cord injuries.

Paralysis caused by spinal cord injuries--such as that suffered by actor Christopher Reeve almost a decade ago--remains one of medical science's most vexing problems. Despite years of study of the relationship between such injuries and human mobility, physicians have had only marginal success in helping paralysis victims regain full use of their bodies. But promising research at the University of Maryland could point the way toward solving some of the key mysteries of paralysis.

Avis Cohen, a professor of neuroscience and cognitive science with a joint appointment in the Institute for Systems Research, expects a breakthrough will happen as she and other scientists learn more about the complex network of nerves, tissue and bone that make up the spinal cord itself.

To date, Cohen says, most paralysis research has focused only on the brain and its ability to send clear signals to the body to elicit motion. What scientists have not given sufficient attention to, she says, is the important role that the spinal cord plays in processing those signals and coordinating the movement of muscles within the body.

"What people fail to appreciate is the capacity of the spinal cord to do a lot on its own," Cohen says. "The spinal cord is actually quite a complicated and impressive structure. In this country, especially, we're just too focused on the brain and not giving enough credibility to this lower structure, the spinal cord, which is very smart and very capable."

Cohen's argument is bolstered by her work with lampreys, one of the Earth's oldest aquatic vertebrates. In her university laboratory, Cohen and her research associates study lampreys' spinal cords after they have been removed from the animals' bodies. "The lamprey's nervous system can be put in a dish and kept alive for days," she says.

Even when removed from the body, including muscles and brain, the lamprey's spinal cord continues to respond to stimuli by producing the motor signals that are seen during swimming--even though no movement is possible. "The spinal cord is perfectly happy in the dish, and it will swim for hours and hours," Cohen says. "It is responding without any information from the brain telling it what to do. It is responding instead to a simple chemical impulse."

The ease with which this can be done has opened a number of other research avenues for Cohen, including some that touch directly on questions about human paralysis. For example, she has found that lampreys with damaged or broken spinal cords can show a remarkable ability to recover swimming ability even though some types of brain signals fail to regenerate. But the success of the regeneration--whether it is functional or dysfunctional--depends on a variety of other factors, including environmental conditions like temperature as well as biochemical processes within the spinal cord itself.

In recent years, Cohen has begun working with a team of engineers to apply some of the principles of her research to silicon chips. If successful, the work could lead to the development of neural prosthetic devices that, when implanted in the body, help to stimulate neurons in the spinal cord by way of electronic impulses.

Cohen cautions that neural prosthetics may have a difficult time gaining acceptance by spinal cord injury patients, in part because of a strong bias toward solutions that don't involve artificial aids.

"People would rather have it work medically," she says. "There would be fear among patients" that the prosthetic device would make them feel like robots.

Nevertheless, Cohen says she is confident that a major breakthrough in treatment and rehabilitation of spinal cord injury patients is coming in the near future. "I hope to see it in my lifetime," she says. But, she cautions, "science has a way of putting landmines in the way of progress."
--Daniel Cusick