When I first started treating stroke patients in the 1970’s, physicians and therapists believed that the brain was “hard wired” as soon as the“critical periods” of early childhood ended. As a result, some believed that therapy just provided patients with compensatory “tricks” or workarounds. Many professionals I worked with contended that the adult brain was essentially unchangeable, especially after a stroke.
What the Research Says
Neuroscience research over the past three decades has conclusively shown the exact opposite – the human brain is experience-dependent and actively changes throughout our lives. In fact, the human response to therapy, at its core, reflects the capacity of the brain to adapt to changes in the environment. Neuroscientists have found that this neuroplasticity is the most fundamental property of the human nervous system. Speech, physical, occupational, and psychological therapy work because therapists change brains. But is this also true of the brain that has suffered a stroke?
The good news, recent research says “yes.” A stroke doesn’t cause a decrease in the brain’s adaptability to experience, and it may actually increase the brain’s ability to stabilize weakened connections while forming new connections.
Damage From Stroke
A stroke causes two kinds of damage. The brain cells in the region where the stroke occurred die due to lack of oxygen. Many scientists are just starting to understand that there are other effects to the brain that are just as destructive. Both the brain cells in areas surrounding the stroke and brain cells in very remote regions may be dysfunctional.
The immediate problems that occur in surrounding and remote brain regions result from two other problems. First, when a neuron dies, the neurons that connected with that cell lose their connection. This causes those cells to either stop firing or fire in a maladaptive way. Second, cells in remote areas can be affected by the lowered brain metabolism and altered arterial blood supply that occur after a stroke. These destructive brain processes are referred to as diaschesis. Fortunately though, the brain also has automatic healing capacities that begin to correct this early damage – referred to as spontaneous recovery.
Spontaneous Recovery and the Role of Therapy
Functional spontaneous recovery involves three interdependent phases:
- Reversal of diaschesis, activation of cell genesis, and repair
- Change in the properties of existing neural pathways
- Neuroanatomical plasticity leading to the formation of new neural connections
Scientists have found that therapy is critical to this ability of the brain to heal during the spontaneous recovery stage. Therapy is so important during spontaneous recovery because the brain is so actively changing and dependent on experience, maladaptive changes can result from the wrong kind of stimulation.
Take for example, left-sided hemispatial neglect, a common symptom of a right hemisphere stroke. This neglect causes a patient to ignore information on the left side of space during reading, writing, eating, conversing, and motor acts. Over time, the more the patient ignores the left side of space the better the brain gets at that.
- During early stages of recovery, nurses and therapists may see that symptoms of the neglect continue to worsen and patients may begin to deny that there is any problem at all.
- Patients may even fail to recognize that they have a paralyzed limb on the neglected side.
- They often start to stare down and to the right ignoring people and barriers around them.
- Social relationships can falter; patients may feel more and more isolated and detached from the surroundings.
- Patients may state that no one has visited them or worked with them in therapy despite hours of intervention.
- They may also become less and less motivated to change.
The brain seeks to repair itself when the environmental demands signal to the brain that something is wrong with the transmission. So, by intervening early with therapy that encourages the patient to attend to the left side of space – the left side of a clock for telling time or the left side of a page for reading – and to pay attention to a person’s entire face during communication, we can ensure that the healing brain will receive more information on the importance of the left side of the world. As a result, the brain is more likely to reestablish connections that facilitate attention to the left side of space.
Benefits of Therapy Beyond the Spontaneous Recovery Period
It’s not just during spontaneous recovery that therapy is essential for constructive neuroplastic change. New research indicates that long after the spontaneous recovery period ends, the brain remains experience dependent and therapy can be beneficial. The human brain essentially gets better and better at what it can do easily, and worse and worse at what is difficult. That is, unless something or someone forces the brain to do the hard work of learning new skills or improving damaged ones – i.e., therapy.
Continued therapy enhances the two processes that are active in all normal learning: changes in the properties of existing neural pathways, and the formation of new neural connections. But after a stroke, these processes require a skilled therapist to determine “what” needs to be done, how often, and for how long. If tasks are too difficult, the patient may give up and stop trying. If the tasks are too easy, they will not push the brain to change. The best therapy pushes a patient with an 80-20% margin of success. A task that can be accomplished adequately about 80% of the time but remains a challenge 20% of the time seems to challenge the brain to change without discouraging or frustrating a patient.
Therapy changes brains after stroke by pushing patients to do the hard work of recovery. This in turn forces the brain to strengthen important existing connections and re-wire the brain where necessary to enable resumption of a lost function. Therapy can have beneficial effects for many months after spontaneous recovery ends.
- Bryck & Fisher (2012) Training the Brain: Practical Applications of Neural Plasticity From the Intersection of Cognitive Neuroscience, Developmental Psychology and Prevention Science. Am Psychol. 67(2): 87–100 Review as applied to perdiatrics
- Kerr, AL, Cheng, SY, Jones, TA (2011) - Experience-dependent neural plasticity in the adult damaged brain. Commun Disord. 44(5): 538–548
- Kleim, Jeffrey (2011) Neural plasticity and neurorehabilitation: Teaching the new brain old tricks. Journal of communication disorders, 44(5)
- Kleim, J. and Jones, T.A. (2008) Principles of experience-dependent neural plasticity. JSHR 51(1), S225-S239.
- Murphy & Corbett (2009) Plasticity during stroke recovery: from synapse to behaviour. Nature Reviews Neuroscience
- Pekna,M., Pekny, M., Nilsson,M.(2012) Modulation of Neural Plasticity as a Basis for Stroke Rehabilitation. Stroke 43: 2819-2828 Thorough review for all disciplines
- Takeuchi, N & Izumi, S (2013) Rehabilitation with Poststroke Motor Recovery: A Review with a Focus on Neural Plasticity. Stroke Research and Treatment. Volume 2013, Article ID 128641 Excellent review for PT and OT
- Warraich Z, Kleim JA. (2010) Neural plasticity: the biological substrate for neurorehabilitation. PM R. 2:S208 –S219.