It’s a concept that would have been thought impossible fifty years ago. Back then, scientists believed the brain’s structure was fixed and unchangeable after early childhood. But because of advances in brain stimulation and imaging technology, such as magnetic brain stimulation and functional magnetic resonance imaging (fMRI), it’s become clear that the brain is supple and adaptable, capable of reorganizing itself throughout life and creating new neural pathways to adapt to its needs.
This incredible adaptability is called neuroplasticity, says Dr. Robert Chen, senior scientist at the Krembil Research Institute in Toronto and a neurologist at the Toronto Western Hospital.
“Neuroplasticity is the ability of the brain to change, in response to things like memory and learning,” says Dr. Chen. “Children’s brains are often more plastic, but in the past people didn’t appreciate how plastic the adult brain is. We now appreciate that much more than we used to.”
Repeating a behaviour or learning something new causes the brain to grow more connections among neurons and to reconfigure neural pathways. In other words, whether we’re learning to walk, mastering a musical instrument or becoming fluent in a second language, our “plastic” brains change as we learn new skills.
“Plasticity is also a way for people to recover from a stroke or other types of brain injury from diseases,” notes Dr. Chen. When a neural pathway is blocked because of damage, neuroplasticity helps the brain find and strengthen other, alternate pathways.
But if the brain is so naturally plastic, can it be coaxed into changing by stimulating it in a particular way? And could boosting neuroplasticity in people with neurodegenerative diseases or brain injuries help them regain abilities they’ve lost?
These are the questions that Dr. Chen is working on answering. By harnessing the power of neuroplasticity through brain stimulation, he hopes to improve the lives of stroke patients and people with debilitating movement disorders like Parkinson’s disease and dystonia.
In Parkinson’s, deterioration of nerve cells in the brain produces a vital brain chemical called dopamine. Patients experience tremors, stiff muscles and problems with balance and movement. In dystonia, the cause is thought to be a problem in the basal ganglia, the area of the brain responsible for initiating muscle contractions. People with dystonia experience involuntary muscle contractions and spasms.
Dr. Chen’s lab is currently investigating the therapeutic use of repetitive transcranial magnetic stimulation (rTMS), a non-invasive and painless way of stimulating the brain.
“With rTMS, we apply a magnetic pulse on the top of the head and the magnetic waves penetrate the scalp,” explains Dr. Chen. “We can tweak it with different parameters, using strong or weak stimulation. But I think even more important is the pattern. We deliver trains of pulses to the brain, and the effects depend on the pattern and the frequency of these pulses.”
Dr. Chen says brain stimulation can “change the balance” of neural pathways. In the short term, it allows the brain to use pathways that were already there, but weren’t working.
“In the longer term, we think that there is also potential for the generation of new pathways,” he says.
At Dr. Chen’s lab, they are experimenting with different patterns of rTMS to discover which are most beneficial to patients. For example, one method, called theta burst stimulation, consists of three bursts of pulses repeated every 200 milliseconds. They are also investigating combining rTMS with other, more invasive brain stimulation techniques, like deep brain stimulation (DBS). In DBS, an electrode is surgically implanted to deliver electrical stimulation directly to specific areas of the brain.
“When combining the deep brain stimulation with the magnetic stimulation, we are able to induce brain plasticity, but we have to time these pulses precisely,” says Dr. Chen.
Patterns can depend on an individual’s particular disorder or symptoms. In some cases, like stroke or Parkinson’s, researchers are working to restore or increase plasticity, while in other cases, such as in dystonia, they are trying to modulate or reduce plasticity gone rogue.
“Certain patterns of brain stimulation tend to make the brain even more excitable, and certain patterns of stimulation tend to make the brain less excitable,” says Dr. Chen.
Dr. Michelle Ploughman is the Canada Research Chair in rehabilitation, neuroplasticity and brain recovery at Memorial University in St. John’s, N.L.. Her lab is also exploring the power of neuroplasticity, in the context of stroke patients and people with multiple sclerosis.
She explains that after an insult to the brain such as a stroke, there is a “window of neuroplasticity” of about 12 weeks. During this time, the body naturally produces a burst of neurotrophins – proteins that support dendritic branching, or the creation of new connections between synapses.
“You have about 12 weeks to maximize the recovery that’s available,” says Dr. Ploughman. “So you want to make sure that you get the rehabilitative treatment at that time that helps the right networks connect.”
Exercise and rehabilitation therapy can help promote dendritic branching, says Dr. Ploughman, but her lab is looking for other ways to boost neuroplasticity in that crucial post-stroke period. Like Dr. Chen, Dr. Ploughman and her colleagues are studying brain stimulation techniques like rTMS. They are also exploring the potential of drugs to boost neuroplasticity.
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“There were studies in Europe and the US about using the drug fluoxetine, which is Prozac, an antidepressant,” she says. “The theory is that it increases one of these neurotrophins called brain-derived neurotrophic factor. The other thing is stem cells – maybe there’s potential for stem cells that perhaps could be modified to increase their production of neurotrophins.”
Dr. Ploughman says that the answer may ultimately be found in a combination of multiple interventions.
“For example, the ideal treatment in the future might be a stem cell transplant, accompanied by brain stimulation and rehabilitative treatment at the same time.”
Dr. Ploughman says they are also exploring the benefits of boosting neuroplasticity in people with multiple sclerosis (MS). In MS, the disease attacks myelin, the protective covering of the nerves, causing inflammation and damage. Symptoms can include extreme fatigue, lack of coordination, weakness, vision problems, impaired sensation and cognitive impairment.
While the use of drugs to help people with MS have improved over the years, Dr. Ploughman says they are excited to take what they’ve learned from stroke and “cross-pollinate” – apply that knowledge to help young people with MS recover their lost abilities. Dr. Ploughman’s lab isn’t testing brain stimulation as a treatment for people with MS. Not yet, she says.
“But you can easily see how you could say, ‘Why don't we just jump from one highway to the next – learn from what we’ve done in stroke and test it?’”
When it comes to measuring the efficacy of brain stimulation in boosting neuroplasticity, Dr. Chen says that study results have been very promising. In a recent multi-centre study, researchers employed both real stimulation and placebo stimulation, treating Parkinson’s patients in daily sessions of rTMS for two weeks. They found that there was an improvement in the movement of patients with the real stimulation as compared to the placebo group.
“It’s still early days,” notes Dr. Chen. But he foresees a future where patients could come in regularly for rTMS treatments. (rTMS is currently Health Canada-approved to treat patients with depression, but not yet for movement disorders.)
“I don’t think [stimulation] is going to replace medication. But there are limits to medication, and many problems we cannot solve,” says Dr. Chen.
“We will have to do more testing, but I’m hoping that if we can develop this further, it has great potential to further improve [patients’ lives].”
This content was produced by The Globe and Mail's Globe Edge Content Studio, in consultation with an advertiser. The Globe's editorial department was not involved in its creation.