Focused arm and hand training after stroke promotes recovery and alters brain maps is one mouthful of a title. However it is important to walk down this ‘neuroplasticity research history’ with you because the work of key researchers has laid an important foundation from which we continue to benefit. Read this title again. ‘Focused’ means not one hour per day but many hours per day; ‘Skilled’ means that the training employs real world activities that require progressively more difficult movements; ‘Promotes recovery’ means that we see re-emergence of lost abilities-not improvements in the skill of the opposite limb or unaffected muscles (not compensations); and ‘Alters brain maps’ means that this treatment helps rewire or sculpt brain circuits.
[A word about stroke research and terminology: I will often refer to neuroplasticity in stroke because this is the field that has made the most advances in neuroplasticity research. Stroke is a loss of blood supply to a specific brain region. This loss of blood supply or ’ischemia‘ (is key mee yah) can be caused by a clot or a blockage or a bleed. This in turn leads to a group of brain cells dying- an ‘infarct’. In fact ischemia and infarct are common in other brain insults such as trauma, infection, surgical intervention to remove tumours, and dementia. ]
Now let’s get back to the story… which is a story about the critical work on our topic by Dr. Randolph Nudo at the University of Kansas Medical Center published in a number of high profile research journals in the mid-1990’s. Of particular importance is the 1996 paper in Science: ‘Neural substrates for the effects of rehabilitative training on motor recovery after ischemic infarct.’
Nudo developed a precise method to map the regions of the brain responsible for movement of the hand and arm in monkeys. It involved opening the skull of the monkey (craniotomy) and using a microscopic-sized needle to apply an electrical impulse to the surface of the brain. This intra-cortical microstimulation (ICMS) technique was used to observe the animal’s limb movement with stimulation and derive a detailed map of areas of the brain responsible for movement of the fingers (digits), forearm, arm and shoulder (Read some of the posts on brain mapping for a refresher like Penfield: Brain mapping pioneer). After mapping the hand and arm regions in monkeys, Nudo and colleagues would then cauterize a tiny artery that supplied the hand brain map to cause a small ischemic infarct (a stroke but also a brain injury) and paralysis of the monkey’s digits. In the first part of his study, animals were returned to their group cage where they moved about, groomed and socialized but with noticeable deficits in the affected limb. Nudo simply observed the animal’s natural recovery and then remapped the brain a few months later. What he found was that the former hand and digit map was ‘taken over’ by forearm and shoulder brain regions (Read the post on Brain Map Robbery for relevant background). The animals did not recover hand function.
In part 2 of his study, instead of allowing the animals to recover on their own in their cages, he developed two rehabilitation strategies. One involved the monkey wearing a jacket for most of the day that constrained the use of its good arm to force it to use its weaker arm and hand for its daily activities. The second rehabilitation strategy involved using the same jacket but supplementing that with daily training. This training involved providing food pellets in progressively smaller bowls. The monkey had to reach through its cage bars to retrieve the food pellet. As it
accomplished the task in larger bowls, the pellets were provided in smaller bowls. This forced the monkey to use the tips of its fingers to get the pellet rather than just scooping it up.
So what happened? Nudo and colleagues found that when animals were remapped using the ICMS technique, only the jacket and training together prevented loss of the hand brain map. This most intense rehabilitation paradigm resulted in the best recovery.
These results raise some interesting questions.
Do the findings in monkeys apply to the human condition?
This was a very small brain injury to a discrete area; does it apply to more extensive brain injury?
Do people receiving rehabilitation after brain injury receive training this intense?
Could the same approach of ‘forced use’ and intensive training apply to other impairments after brain injury like those in
cognitive processing and language?