I have a friend who works in humanitarian aid and has raised her daughter in multiple countries. By the age of seven, her daughter was fluent in English, Spanish, Bosnian, Serbian, Albanian, and Tagalog. Why is it that kids "are like sponges" and seem to pick up foreign languages just by being exposed to them? The answer lies in neuroplasticity. Neuroplasticity is our brain's ability to develop new neuronal pathways and networks based on the input we provide it, that is to say, the experiences to which we expose ourselves.
We have known children to have this capability, especially within the first 7 years of their lives known as the "critical period". But what about adults? And older adults for that matter? It wasn't until relatively recently that we discovered the adult, and yes the older adult, brain has the capacity to change its neuronal structure (new neurons) and function (how they operate).
The Homunculus (now 3 times really fast)
Through the experimental graces of rats, monkeys, and even owls and raccoons, almost a decade of neuroscience research has taught us that specific brain regions are responsible for specific sensory processing (feeling) and motor responses (doing). For example, when you dip your toe into the cold ocean, the temperature receptors on the skin of your toe send signals up a neuronal highway to the very specific region in the brain responsible for sensations of that particular toe. Other nearby regions in the brain receive sensory information from other toes, or from the bottom of your foot, or your ankle, all the way up to the tippy top of your head. Likewise, if you wiggle that toe in the cold water (cause you LOVE cold water dipping like me!), there is a very specific part of your brain allocated to the movement of that toe that sends signals down a neuronal highway to wiggle that toe, or wiggle the other toes, or the foot, the ankle, or your entire body. Scientists discovered this over years of "mapping the brain". Stimulating one part of the brain, and noting which body part moved, which muscle contracted, allowed them to map the motor cortex. Or stimulating a part of the body, and noting which part of the brain activated, allowed them to map the somatosensory cortex. A pictorial summary of these maps, known as a homunculus, are below.
Neuroscientists Michael Merzenich, Jon Kaas, and Karl Lashley took this knowledge a step further and discovered that these maps are not set in stone or written in ink, but rather drawn in say...chalk. Meaning, that these maps can change! Lashley, while mapping the motor cortex of one particular monkey (let's call him Yek), discovered that Yek's sister, Nom, had a different motor map. When he compared Yek and Nom's motor maps to other monkeys of the same species, he found that all of their motor maps had significant variations. He also found that if he re-mapped Yek's motor cortex and compared that to a previous map of Yek's motor cortex, they were different! He concluded that these motor maps are adaptable and depend on how much a particular movement is performed. For example in humans, the motor map of the shoulder (located near the top of that homunculus) of a regular swimmer will be physically larger than that of someone who doesn't use their shoulder muscles as much, or will even be different in that same swimmer if they stop swimming. Can you imagine the size of Katie Ladecky's shoulder motor map???
Likewise, Merzenich and Kaas, while mapping the somatosensory cortex in monkeys noted that if you amputate one of the monkey's fingers, the somatosensory map of that finger will be taken over by the somatosensory maps of the remaining fingers. They also discovered that if you re-attached that finger, and encourage the monkey to use that finger in various activities, over time it will reclaim it's brain territory and establish it's somatosensory map once again! Tell me this isn't blowing your mind? Honestly, even as old news to a neuro-geek like myself, my mind continues to be re-blown as I write this.
Anyway...why am I, a physical therapist, concerned with all of this? Well, as a neurological physical therapist, this is the basis for helping people recover movement function after a brain injury, stroke, or vestibular condition. So, how do we do that?
How can I change my brain? Principles of neuroplasticity
Leveraging the findings of multiple studies in neuroplasticity, Kleim and Jones outlined ten principles of neuroplasticity that we, as physical therapists, use to help people rebuild their brain after injury. Click the arrows to learn more about each principle.
Use It or Lose It
Remember those monkey's that had one of their digits amputated? Unable to use that digit, the part of the brain responsible for the feeling and movement of that digit was lost and taken over by the other digits that were being used regularly. If you don't use a particular movement pattern or stop doing it you will lose it. So first thing in therapy, is simply to start doing the thing you want your body to do and to keep doing it.
Use It and Improve It
Specificity
Repetition Matters
Intensity Matters
Time Matters
Salience Matters
Age Matters
Transference or Generalization
Interference
“Nothing inspires more reverence and awe in me than an old man who knows how to change his mind.”
― Santiago Ramón Y Cajal ("Father of Neuroscience")
References
Kleim JA, Jones TA. Principles of experience-dependent neural plasticity: implications for rehabilitation after brain damage. J Speech Lang Hear Res. 2008 Feb;51(1):S225-39.