Dr. Eric Wassermann sat in the middle of the lab at the National Institute of Mental Health as Dr. Mark George placed a magnetic coil against his head. The two had been at the drawing board all day, attempting to map the brain’s complicated inner workings onto the smooth surface of Wassermann’s skull.
These trial-and-error experiments marked the beginning of their attempts to use brain stimulation as an alternative therapy for neurological conditions. In their research, Wassermann and George had stumbled upon the formula for a revolutionary medical treatment — one which relied on the idea of neuroplasticity.
For nearly two decades, neuroscientists believed that human brain development plateaued at the age of 25, following steady growth during adolescence. While early MRI studies popularized this idea, many researchers now argue that those findings were oversimplified. Instead, modern neuroscience emphasizes the brain’s lifelong “neuroplasticity,” or its ability to adapt, recognize and form new neural connections in response to learning, experience, injury and environment.
Dr. Lara Boyd, the brain behavior lab director at the University of British Columbia, and Wassermann, a leading researcher at the National Institute of Mental Health, both affirm that understanding and leveraging brain plasticity could revolutionize treatment for mental injuries and conditions. Their respective research demonstrates that the brain is never a fixed environment — instead, it’s a highly dynamic system capable of structural change well into adulthood. By showing that targeted interventions like brain stimulation can physically alter neural pathways, their work shifts the medical paradigm from symptom management to rehabilitation. Beyond medicine, neuroplasticity has also gained traction in self-improvement efforts.
In the first few years of life, a child’s synapses — the connections between neurons that facilitate communication in the nervous system — grow from about 2,500 to 15,000 per neuron, enabling rapid learning and injury recovery. Inevitably, the brain becomes less malleable in adulthood, but modern research on this process shows that adults can still facilitate change through learning new, challenging skills — or through technologies designed to stimulate the brain directly.
One prominent brain stimulation technique is Transcranial Magnetic Stimulation (TMS). A technician places an electromagnetic coil against the patient’s head, generating magnetic pulses that pass through the brain and create tiny, localized electrical currents. These currents help restore communication between parts of the brain that might not be working properly, making it easier for patients to think, feel, and function normally. The therapy is non-invasive and is commonly used to treat patients with treatment-resistant conditions, as well as those who cannot tolerate certain medication side effects. TMS encourages the brain to form new connections, allowing it to develop healthier patterns of activity that can support lasting improvements in mental health. In 2008, the FDA approved TMS as a treatment for depression, and the therapy has since evolved to treat a wider range of conditions, including obsessive-compulsive disorder and migraines.
Neuroplasticity is a vital property of the brain, but it can operate in both negative and positive ways. For those with depression, neuroplasticity can reinforce harmful habits or thinking processes. The brain adapts to make any repeated process more efficient, which includes long-term stress and depression. This effect can make the brain rigid and hinder synaptic growth in newer, healthier neural pathways. TMS harnesses that same neuroplastic quality, instead using it to create a channel out of this engraved emotional state by facilitating growth in underdeveloped pathways through forced stimulation.
Wassermann, who pioneered many fundamental techniques of TMS and collaborated on the first clinical use of TMS in the treatment of depression, said that growing any particular neural pathway requires practice. For TMS therapy to have lasting effects, it has to be paired with a behavioral component, like talk therapy.
“It’s kind of like using TMS as a boost to increase the representation of a muscle in the motor cortex, something you could do by practice alone, but maybe this makes it a little easier,” Wassermann said.
This technique is rooted in Hebb’s Law — the idea that when two neurons are activated simultaneously, the connection between them strengthens. Neurologist Clara Shatz famously summarized this mechanism as nerves that “fire together, wire together.”
Pairing TMS with other therapies can directly apply Hebb’s principles by physically forcing certain neural networks to fire simultaneously. This treatment approach differs from traditional antidepressants, which adjust the levels of neurotransmitters throughout the entire body. A stimulation approach represents a neurologist’s view of the brain, while psychiatrists have historically focused on modifying brain chemistry through medication to influence mood and behavior.
“One of the things I’m proudest of is having contributed to a synthesis of those views, getting the psychiatrists to think more in circuit terms, and getting neurologists more interested in emotional behavior,” Wassermann said.
Despite decades of research, scientists are still working to understand exactly how neuroplasticity operates within the brain. Studies and conclusions involving neuroplasticity remain fluid because the brain is an extremely dynamic environment with countless interacting systems, making the process difficult to define fully.
Boyd simplified neuroplastic change into three main categories: chemistry, structure and function. According to Boyd, the fastest and easiest thing for humans to do is change our brain chemistry, which happens when our nerve cells interact by sending chemical signals.
“When we’re learning something or forgetting something, we are changing the excitability of neurons by changing the amount of chemicals that are available,” she said. “That is why we think this is the formation of a short-term memory.”
To form longer-term memories that can be recalled, structural change is necessary, Boyd said. This involves their neurons growing new connections, which happens when the number of branches on a neuron increases.
To rehabilitate stroke victims, Boyd’s lab focuses on structural and functional changes, combining targeted stimulation with repetitive movement to encourage the brain to rebuild pathways more effectively. This rehabilitation model, similar to Wassermann’s, relies on the “fire together, wire together” philosophy.
The main obstacle Boyd presented in using brain stimulation therapy is determining what makes certain treatments effective for specific people. While TMS currently works for about 60% of patients, there is no established biomarker to determine who falls under the 40% where it is ineffective. Fine-tuning diagnoses would enable patients to skip the trial-and-error process entirely. By identifying genetic or structural indicators beforehand, clinicians could map out custom neural targets from day one.
“There’s a window after a stroke where your brain is really neuroplastic,” Boyd said. “If we mess around giving you the wrong therapy, we not only have wasted your time and money, but we may have missed a real opportunity and you’re not going to recover as well as you might have otherwise.”
Similarly, with stroke victims, variability in the brain applies to a new field known as educational neuroscience. Everyone is capable of learning, as every brain is plastic — but that happens through varying timelines and methods. In traditional learning models, educators apply standardized, uniform methods to all students. However, rigid curricula often fail to accommodate the diverse range of cognitive profiles found in a single classroom.
“I find it very frustrating because you have very bright kids who are wasting their time and a subset of individuals who are labeled as dumb or unable,” Boyd said.
Actively fostering neuroplasticity enables the brain to reroute and build neural connections more easily, offsetting overall cognitive decline. Enhanced plasticity can also improve mental health by breaking negative thought patterns and promoting emotional adaptability.
Everyday activities such as exercise, socialization and sleep all provide sensory input and rewire the brain. Challenging activities are most effective at increasing plasticity because they prompt significant cognitive load: a state of mental strain where the brain is pushed past its comfort zone, forcing it to adapt. To manage this strain, researchers look to the Challenge Point Framework. This behavior model suggests matching the difficulty of an activity with the learner’s current skill level to optimize information retention and promote structural change with minimal frustration. This framework highlights why self-directed, progressive learning can be so impactful.
Sophomore Finley Jones began to pick up a variety of hobbies during the COVID-19 pandemic, like juggling, solving Rubik’s Cubes and translating nautical flags to pass the time. Jones said she now feels the most at ease when she puts her energy towards learning something new.
“My favorite part of learning a new skill is when I can do it in the background,” Jones said. “Sometimes it’s hard to focus all my energy on something, and it’s good to know firsthand that things get easier with practice.”
Since the pandemic, Jones said learning new tasks has only become quicker and easier — by tackling a variety of skills, she is training her brain’s capacity for change.
Jones’s experience illustrates the reality of modern neuroscience: by consistently engaging in varied, high-effort cognitive challenges, individuals can intentionally prime their brains for greater flexibility. This baseline of adaptability is exactly what clinical tools like TMS aim to artificially jumpstart in underperforming brains.
Ultimately, neuroplasticity research reveals that the brain is not a finished structure, but an organ constantly rewriting itself in response to experience, effort and environment. That possibility carries enormous promise for medicine, education and mental health, but researchers caution against treating any scientific explanation as complete. Wassermann noted that many early TMS breakthroughs happened before scientists fully understood whether the treatment worked at all. In many ways, the discovery came before the theory. As neuroscience advances, that uncertainty may be one of the field’s greatest strengths. The brain remains a highly dynamic domain, and understanding it requires scientists to stay just as flexible as the organ they study.
“If we are just going to assume our mechanistic theory for how something works is correct, it can propagate bad ideas and lead down blind alleys,” Wassermann said. “Just because something worked, doesn’t mean it worked the way you think it did.”
