Training the brain to learn a new dominant hand

I began working with stroke patients, who often have, as one of their more common difficulties, trouble using their hands. And one of the things that I became very interested in is how people compensate for loss of hand function on one side by being forced to use the other side. One of the common ways of rehabilitating stroke patients who have such a unilateral hand impairment is to try and force them to use the impaired side. It's called "constraint-induced movement therapy." We looked at amputees as an example of just what can be achieved if one is forced to only use a single hand for years or even decades. We focused our efforts on amputees who had lost their right dominant hand, because these individuals provided a window into just what's possible in terms of compensating with a non-dominant hand. And we chose drawing because we had some ways to quantify drawing. We could have people draw on a digitizing tablet and record the speed and accuracy with which they performed. And I think a very exciting result that we obtained was that on average, our group of individuals who had lost their right dominant hand more than 20 years ago were performing as accurately and as quickly as right –handed individuals of similar age and similar gender. And I think that's very telling, and it suggests that with enough practice, it's possible to have your non-dominant hand acquire these precision movement control that you normally have a big advantage with when you're performing with your dominant hand. The second part of the study was to ask what are the brain mechanisms that are involved in this kind of compensation. And what we were able to show is that the areas that used to experience sensations coming in from that amputated right hand and that used to send signals out to control movements of that right hand began to serve the functions of that left hand. In other words, right-handed individuals forced to use the left hand for a long time were using not only the areas of the brain that receive sensory information from and control movements of that left hand, but were able to take advantage of the areas that used to be devoted to the use of their dominant hand.

Another sort of interesting parallel here is when stroke patients have an impairment of either hand, but gradually get the functions back into that hand, what we see is that it looks like they are using both sides of the brain. So in other words very similar to our amputees who are compensating with their non-dominant hand, stroke patients as the function comes back to that initially impaired hand seem to start to use both sides somewhat as well.

We want to understand better how our finding might generalize to other behaviors, other functions of the hand. And we also work with some people who are former amputees, individuals who have had a transplant of a hand. So, lost a hand and years or decades later received a transplant, much like someone might receive a kidney or a lung transplant. There are only 50 or so of these individuals in the world now, but we are very privileged to have the opportunity to look at how their brains adapt and compensate. Lee Lassiter is the lead technologist in the Brain Imaging Center, and runs the MRI as part of Frey's research. "The scanner we have here at the Brain Imaging Center is three-tesla, that is twice the strength of what normal clinical scanners," he said. "That helps with the clarity of our images."