There's Hope for Some Stroke Victims: CI Therapy
The account of Michael Bernstein’s recovery and Edward Taub’s experiments on monkeys, showing how the brain's capacity to reshape itself can be put to use to help some stroke victims, is one of many fascinating chapters in the book The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science, by Norman Doidge (London: Penguin Books, 2008).
The main thesis of the book, now finally accepted by the scientific world after half a century of research, is that the brain can rewire itself by forming new neuronal connections -- in response to brain injury, for instance. This is known as neuroplasticity. Due to new approaches harnessing the brain’s neuroplastic capacity, there’s finally treatment for many brain injuries where traditional approaches offered little hope and help.
Dr. Bernstein's stroke recovery
Like many before him, Dr. Bernstein had a stroke at fifty-four that affected much of his motor cortex, and found himself paralyzed on the left side of his body. Traditional physical therapy didn’t help much. He could barely use his left hand, and had to use a cane. A formerly ambidextrous man, who could perform a surgery with his left hand, he was now incapable to bring food to his mouth using the affected hand. He also couldn’t drive.
All of which brought him to the Taub Therapy Clinic, into a program of constraint-induced (CI) (movement) therapy (CI therapy). After two weeks of intensive CI therapy Dr. Bernstein could write with his affected hand again.
Hiking can become an option again after a serious stroke
Image source: Pixabay
The man who led the way to make it possible is Dr. Edward Taub, neuroscientist, Professor of Psychology at the University of Alabama at Birmingham.
While he was a graduate student at Columbia and then at New York University, Edward Taub veered away from the prevailing behaviorist leanings in psychology. He found a job as a research assistant in a neurology lab and soon he was working there to show that the ability of a monkey to use a deafferented arm was not lost for good. As he demonstrated that, he also refuted one of the major theories in neuroscience.
But first, a few words about deafferentation. It is a surgical procedure that cuts sensory nerves that relay information via impulses to the spine and the brain.
Sir Charles Scott Sherrington (a 1932 Nobel Prize winner), who used deafferentation
Sir Charles Scott Sherrington
Source: Wikimedia Commons
as early as 1895, upheld the idea that our movement is always due to spinal reflexes.
What Sherrington showed in an experiment he devised together with F.W. Mott was that a monkey whose arm was deafferented not only didn’t feel anything in that arm, but also stopped using it. He then offered in support of the fact that the deafferented monkey wasn’t moving his arm the idea that movement is generated by spinal reflexes. As Norman Doidge points out, it soon became an all-encompassing theory: all movement is based on reflexes, and all behavior on environmental stimuli.
It held water . . . until Edward Taub came along.
What Edward Taub showed, with the help of neurosurgeon A.J. Berman, in one of his firsts deafferentation experiments, was that monkeys can be made to use their deafferented arms again. He achieved that by constraining the movement of the good arm. Acting on an intuition and an easy but powerful experiment, he broke new ground in neuroscience, invalidating as he did so Sherrington’s theory.
He also started thinking more and more about the role of the brain in helping the monkey use the deafferented arm or a stroke victim the affected arm.
He forged ahead step by step devising new experiments on monkeys. He first deafferented both arms. The monkeys started using them in order to survive, as he intuited. Then he deafferented the spinal cord. The monkeys now had no spinal sensory reflexes. Still they were able to use their limbs. That was the end of Sherrington’s theory.
From deafferented monkeys to stroke victims
While strokes are different than sensory nerves cut off, as they affect the brain rather than the circuit of sensory impulses from the limbs to the spinal cord, Taub’s experiments to disprove Sherrington’s theory led him to a powerful insight regarding possible treatment for stroke victims.
Maybe, he thought, due to spinal shock, taking some two to six months to wear off, the brain learns not to use the deafferented arm on account of trying to initiate movement and not being able to achieve moment because of impaired neuronal function. Of course this results in a smaller and less active motor map of the affected area as the brain learns not to use that arm.
Taub went back to his experiments where he deafferented the monkeys' arms, only this time he put the bad arm in a sling so that the monkey wouldn’t learn that he couldn’t use that arm (due to spinal shock). Sure enough, shortly after removing the restraint after three months, the monkey was able to use the deafferented arm.
Then he moved on to testing whether he could teach a monkey to use a deafferented arm years after it has learned nonuse. Against many odds, this experiment gave encouraging and life-lasting results as well.
What did this mean for stroke victims?
It meant that they suffered not only on account of their brain injury but also because the brain learns not to use the affected side while it is in cortical shock. This learned nonuse, as Taub calls it, can sometimes impact the function in the affected limbs more than the brain damage itself.
It all led to CI therapy
Constraint-induced therapy for stroke victims was the result of this whole series of insights and experiments. For more about Edward Taub’s career and the many hurdles he had to overcome (involving scandals, courtrooms, financial difficulties, and yes, professors and colleagues who were not ready to let go of paradigms they had built their careers on), read Norman Doidge's book The Brain That Changes Itself. This is just one of the many wonderful stories in there.
To learn more about CI therapy, see the CI pages maintained by the Department of Psychology at the University of Alabama at Birmingham.