For decades, physicians and scientists generally believed that the prognosis for most brain problems was grim. The mainstream view in neuroscience and medicine today is that the living brain is actually “neuroplastic”-meaning that its “circuits” are constantly changing in response to what we actually do. This new “plastic” understanding has major practical implications for how we treat brain problems and maintain brain health. And it has led to some surprising discoveries.
Recent studies have found that exercise can reduce the symptoms of degenerative diseases such as Parkinson’s-a disease that causes patients to gradually lose control of their muscles. Parkinson’s treatment has primarily focused on medication, with exercise as something of a distant runner-up. A study in 2011 published in the journal Neurology bythe Mayo Clinic reviewed the available evidence about exercise and Parkinson’s, in animals and humans. Vigorous exercise for purposes of the study, included walking, swimming and “physical activity sufficient to increase heart rate and the need for oxygen.” The results showed that exercise deserved a “central place” in the treatment of Parkinson’s. A 2014 randomized study of Parkinson’s patients at the University of Iowa, led by researcher Ergun Uc, found that walking three times a week for 45 minutes for six months improved patients’ mood and Parkinsonian movement symptoms; the exercise also decreased their fatigue. Though the patients were on anti-Parkinson’s medication, the improvements could not be attributed to medication alone.
Parkinson’s patients are caught in a tightening noose. They may be helped by fast walking, but fast walking is precisely what they can no longer easily do. And the Parkinson’s patient who cannot walk does not “stay still”-his disease gets worse. Because our plastic brains are “use it or lose it” organs, when walking becomes more difficult, walking less will cause whatever walking circuits the patient still has to wither from disuse. When people with dormant brain circuits try to walk, they fail, “learn” that they can’t walk and stop trying. This is called “learned nonuse,” a phenomenon first seen in human beings who have suffered a stroke-caused by a blood clot or a bleed that cuts off the blood supply and oxygen to brain tissue and killing it.
We have known for more than a century that, after a stroke, the brain enters a state of shock: Neurons die, chemicals leak out of some cells and harm others, inflammation is very active, and blood flow around the dead tissue is interrupted. All of these events disrupt functioning not just where the stroke occurred but throughout the brain. The period typically lasts six weeks or longer.
Physicians once treated such dire problems by waiting six weeks to see what mental functions their stroke patients still had. Since conventional medical wisdom held that the brain couldn’t “rewire” itself or develop new connections, physicians just wanted to discover which cognitive abilities remained after the shock wore off. The rehabilitation that patients underwent merely attempted to reawaken whatever circuits had been spared.
But the plasticity of the brain provides better options. Edward Taub, a neuroscientist at the University of Alabama at Birmingham who discovered “learned nonuse,” has had striking results with patients who have lost the use of limbs from strokes and haven’t gotten better with conventional rehabilitation. He puts the patient’s good arm in a sling (so they can’t use it), for instance, and then incrementally and intensively trains the paralyzed or partially paralyzed arm.
Brain-scan studies show that when patients recover, neurons adjacent to the injury begin to take over from the damaged or dead neurons. More recently, the approach has worked with stroke patients who can no longer speak and with movement problems from multiple sclerosis, cerebral palsy and even movement problems that occur after radiation to the brain for cancer. Learned nonuse seems to occur in response to many brain problems, so dormant circuits, waiting to be revived, are far more common than has been generally appreciated.
Among the most exciting new neuroplastic treatments are those that deal with “the noisy” brain-that is, neurons that fire out of sync or at the wrong rates in conditions like multiple sclerosis and Parkinson’s disease, but also in traumatic brain injuries, learning disorders, conditions on the autism spectrum and some cases of chronic pain. A range of noninvasive methods has yielded radical improvements in all these diseases, allowing scientists and clinicians to “resynchronize” the noisy brain. Our brains work on patterns of electrical energy, and we can change the patterns of brain-firing with sensory input. When you hear a loud pounding beat, for instance, your neurons fire in sync to that frequency, a process called “entrainment.”
Using sound frequencies passed into the ears (which convert patterns of sound energy into patterns of electrical energy), it has been possible to cure some learning disorders and developmental delays, as well as to radically improve the lives of some autistic children. Scientists and doctors using mild forms of electricity to turn on touch receptors in the tongue have been able to reduce the symptoms of MS, Parkinson’s and brain injuries-and even to cure some strokes.
Clinical work in Toronto and studies at Harvard and in Israel have shown that low-intensity lasers applied to the back of the neck can diminish stroke and brain-injury symptoms. And new forms of “conscious walking” that allow Parkinson’s patients to learn to use healthy parts of their brains to take over from damaged areas can sometimes get them moving again.
The basic neuroplastic principle of “use it or lose it” and the benefit of forming new brain connections through intensive learning also apply to people without brain problems. Physical exercise produces some new cells in the memory system, but mental exercise preserves and strengthens existing connections in the brain, giving a person a “cognitive reserve” to fend off future losses and to perfect skills.
Brain exercises developed by the neuroscientist Dr. Merzenich have been evaluated in a National Institutes of Health study, published by George Rebok of the Johns Hopkins School of Medicine and colleagues in the Journal of the American Geriatrics Society. People who did the brain exercises-called Brain HQ-showed benefits 10 years later. They didn’t just improve on the brain exercises; their cognitive function improved in everyday life. Earlier studies showed that the exercises increased a person’s mental sharpness, so they could process information with the speed and accuracy they had when they were 10 years younger. We still have a lot to learn about the brain and its powers of recovery, of course. But increasingly we have the evidence to conclude that our brains have much more dynamic potential than we ever thought possible.
The above has been adapted from The Brain’s Way of Healing by Dr. Norman Doidge, University of Toronto and Columbia University and reported in the Wall Street Journal, 2015.
Paul Block, MD, FACP, FCCP