Motor Learning and Neural Plasticity: Healthy discontent is the prelude to progress
One of the great things about health care is that there is always another question. There is always a patient or client that makes you stop and think, “What am I going to do here?” It is the natural course of problem solving profession to seek new understanding and methods. Mahatma Ghandi phrased it eloquently: Healthy discontent is the prelude to progress.
One of the relatively recent areas of understanding is the principle of neuroplasticity. It is recent in the sense that research is continuously learning more about the brain’s capability. The concept of neuroplasticity has become well known across the broader public sphere courtesy of the Norman Doidge’s 2010 best-selling book “The Brain That Changes Itself”. To quote the sleeve: An astonishing new scientific discovery called neuroplasticity is overthrowing the centuries-old notion that the adult human brain is fixed and unchanging. It is, instead, able to change its own structure and function, even into old age.
So, what do we know about neuroplasticity and how does it apply to motor learning in a therapeutic sense?
Motor learning is defined as “a set of processes associated with practice or experience leading to a relatively permanent change in the capability for movement”. If we want to explain this concept a slightly different way we can turn back to the 1800’s and quote American lecture and poet Ralph Waldo Emerson: “That which we persist in doing becomes easier for us to do, not that the nature of the thing itself is changed, but that our power to do it increased”.
Across this key concept of motor learning is neural plasticity: the brains ability to repair itself using sensory input for new learning. The neurons have the ability to change their structure and function in response to a variety of internal and external pressures (Kleim & Jones, 2008). This includes behavioural training. It is a change in the nervous system that occurs in response to experience. This experience can be accounted for by age, disease, lack of use or use (i.e. for the purpose of this discussion – therapy). These are all forms of experience that can lead to change.
It is important to remember that in the same way new and positive patterns can be learned, so can inappropriate adaptive patterns, if sensory input is damaged (Kleim & Jones, 2008). These inappropriate (and often inefficient) patterns form after a change in regular function. This is why early rehabilitation is so important after stroke and other injury. Teaching positive patterns early on minimises the risk of developing inappropriate compensatory adaptive patterns (Kleim & Jones, 2008).
We know that the brain has the mechanisms to encode experience and learn new behaviours. This is the way a damaged brain can relearn lost behavior in response to rehabilitation. So how do we ‘tap’ into this extraordinary phenomenon in the speech pathology clinical framework?
If we look at Kleim’s 10 Principles of ‘Experience Dependent Neuroplasticity’, we can see how to optimise the brain’s capacity for new learning:
1. Use it or lose it
This is a basic concept; a lack of use can lead to a degradation of function.
2. Use it and improve it
Neural pathways in the brain can be enhanced by training. Certain types of training can actually reorganise representations in the cortex.
3. Specificity
The exact nature of the training determines the nature of the plasticity. Changes in neural function and responsiveness may occur just in the function specifically targeted.
4. Repetition matters
Sufficient repetition of a newly learned/relearned behaviour is often required to lead to lasting neural change.
5. Intensity matters
5. Intensity mattersInducing plasticity requires sufficient intensity. It should be noted however that certain medical conditions might require special consideration as to intensity levels. High levels of intensity in conditions that lead to early fatigue (e.g. Motor neuron disease) may lead to maladaptive behaviours (fatigue and muscle damage).
6. Time matters
Therapy that targets neural restructuring should work anytime. However, there may be windows of time where treatment is particularly effective.
7. Salience matters
The therapy and training must be sufficiently salient to induce plasticity. Therapy should be meaningful. Learning may be enhanced when the movement is purposeful and specific to the behaviour being trained.
8. Age matters
Therapy based plasticity occurs more readily in younger brains, however adult brains are capable of learning, relearning and neuroplastic adaption.
9. Transference
Improvements and plasticity post training in one area may lead to or encourage other simultaneous or subsequent plasticity.
10. Interference
Therapy and subsequent plasticity in one skill may interfere with the ability and performance of another.
(Kleim & Jones, 2008).
Last year, in a conversation with a dentist, he refuted the notion that he ‘fixed’ peoples teeth. He said “I’m just screws and bolts; the body does all the work”. I believe the same principle largely applies to speech therapy rehabilitation. We provide the structure and framework (‘the gym’) and the changes in neural plasticity and capacity is enabled through this structure.
Neural plasticity is a remarkable capability of the human body, not only for relearning after brain damage, but also for learning in the intact brain. Kleim summarises the potential of this relatively new understanding in the broader field of rehabilitation: “The growing understanding of the nature of brain plasticity raises optimism that this knowledge can be capitalized upon to improve rehabilitation efforts and to optimize functional outcome” (Kleim & Jones, 2008).
References
Duffy, J. R. (2005). Motor speech disorders: Substrates, differential diagnosis, and management. St. Louis, MI: Elsevier Mosby.
Kleim, J. A., & Jones T. A. (2008). Principles of experience-dependent neural plasticity: Implications for rehabilitation after brain damage. Journal of Speech, Language, and Hearing Research, 51, 225–239.
