Calling Dr. Doolittle

“Despite evidence that use of the impaired upper extremity has a positive effect on the neurophysiological consequences after stroke, recent studies in rats paint a very different picture. Restricting the unimpaired forelimb in rats with sensorimotor cortex lesions results in prevention of dendritic growth in the uninjured cortex, exaggeration of the neuronal injury, and more severe behavioral deficits.”

RJ Nudo. “Remodeling of cortical motor representations after stroke: implications for recovery from brain damage.”  Molecular Psychiatry (1997) 2, 188–191.

The observation above comes after the author’s brief discussion of Edward Taub’s “constraint-induced movement therapy,” a stroke rehabilitation technique that has proven quite successful in humans.

For the record, I am appalled by Taub’s research technique, which involved cutting afferent ganglia (transmitters of sensory information to the central nervous system) then forcing the monkeys to learn to use their disabled limbs.

Dante Alighieri would have found a spot for Taub.

Was all that cruelty necessary? Couldn’t any moderately impaired stroke patient have told Taub that affected limbs improve with use?

Time and again, I return to the “hard science” literature looking for insights about stroke recovery. I come away with models and brain maps, but little insight. Invariably, I retreat to experience.

How has my brain adapted to tissue loss? I suppose an MRI might tell me what neurons are firing where, but that information won’t help my penmanship or Frisbee toss. Effective rehabilitation requires writing and tossing. Lots of it.

Until someone can convince me that I am wrong, I will continue to understand the brain (and its attendant neural patterns) not as a thought creator, but (as rills left in a hillside’s soil provide evidence of a heavy rain) the result of thinking.

Tipping my hat to Taub, I have typed this post using only (well, almost only) my left (affected) hand.

Regarding this post’s title…  Dr. Doolittle talked to the animals. Dr. D was the original “dog whisperer.” When I was a child, he was also my favorite fictional character. Rather than monitoring the brains of maimed rats, Dr. D would have protected them. Had he arrived too late for that, he would have asked the poor critters how he might relieve their suffering.

Constraint-induced movement therapy

Constraint-induced movement therapy is a technique developed by behavioral neuroscientist Edward Taub. The idea is that, by forcing an attenuated limb to do real-world work, the brain will rewire itself to accomplish the task.

Taub was a center of controversy in the 1980s for his experiments on macaque monkeys during which he surgically cut the animals’ afferent (or sensory) nerve pathways so that information received by a limb could not reach the spinal cord and make its way to the brain. Taub observed that, despite the fact that the motor nerves had been left in tact, the monkeys would not use limbs they could not feel. Taub then came up with the idea of constraining the monkeys’ good limbs, thus leaving them little choice but to use their compromised ones, which they promptly did.

The monkeys’ actions disproved the long-standing theories developed by followers of Nobel laureate Sir Charles Sherrington (1857-1952), who held that all movement is a response to outside stimulus.  This idea dominated neuroscience for decades.

Though Taub’s monkey experiments were limited to afferent nerves, he also had the insight that individuals with traumatic brain injury (such as a stroke) might benefit from limb constraint.

That was a good idea, but it hardly required deafferenting monkeys. Every drummer and pianist knows the benefits of one-hand practice. It’s not that drummers and pianists constrain limbs, but they do work one hand at a time to focus on skill development. Such development (particularly hand independence) will occur much more slowly when only practicing both hands together.

I mentioned in an earlier post that just a few days after my stroke a physical therapy intern at Mass General Hospital had me try to comb my hair with my left hand. The effort was not very successful, but I understood her reasoning—force the arm to work and the brain will work to solve the task.

Was her attempt a good idea? Not for a patient with less determination, I suspect. Failure often leads to surrender. But for me, I mostly just thought the attempt was premature.  Too many skills were required to perform the requested task.

This was a lesson I had learned when trying to sight-read difficult music way over my head. (One sets off boldly, soon begins to sputter, then will either grind to a defeated halt or muddle through to the end for a dubious victory.) Performing is altogether different from sight reading, however. With sufficient tenacity one can generally learn to perform even fiercely difficult music (though not necessarily beautifully or gracefully), but the endeavor will take many months, or years.

Though the hair combing was a failure, I took it as just another difficult “sight reading” experience. A week or so later, while at Spaulding Rehabilitation Hospital, I began to eat my meals with left hand alone. Succeed or starve, I had decided.

It wasn’t pretty, especially with the liquids, but I am still alive. (When my night nurse brought in my meds and a glass of water she would cheerily announce, “Time for your evening bath.”) I have eaten every meal since with my left hand. (Often it is still not pretty.)

Stroke recovery is not “sight reading.” It requires tenacious practice with the goal of flawless performance

My own progress has been slow. At first, I compared my recovery to learning a 1964 percussion piece by Charles Wuorinen titled “Janissary Music,” which, come to think of it, I never did learn well enough to perform, despite a year working on it. (…perhaps that was a poor model upon which to base my recovery aspirations…)

Patients at Taub’s clinic undergo constraint-induced movement therapy for hours every day. Many patients experience considerable improvement. I have no interest in being a Taub patient, but I have considered constraining my right hand so as to force my left to do all the work all the time.  I don’t mind the frustration that could so easily be avoided (I wrote this post using only my left hand), but the time it takes to accomplish basic tasks (not to mention cleaning up the inevitable messes) is terrifically inefficient when trying to meet real-world expectations.