Neuroplasticity in Clinical Practice

Original Author - User:Dinu Dixon

Top Contributors - Stacy Schiurring, Dinu Dixon, Jess Bell and Kim Jackson  

Introduction

Neuroplasticity, also known as neural plasticity or brain plasticity, is the "capacity of neurons and neural networks in the brain to change their connections and behavior in response to new information, sensory stimulation, development, damage, or dysfunction."

It is a normal and ongoing process that occurs across the human lifespan in response to both internal and external stimuli. The concept of neuroplasticity is commonly associated with neurological injuries, but it is integral to paediatric development, learning and skill acquisition, and frequently used rehabilitation interventions. Not all neuroplasticity can be seen as positive or beneficial to human function and ability. Understanding the mechanisms of neuroplasticity is paramount for rehabilitation professionals and will lead to more effective and efficient therapy and improved patient outcomes.

This article provides an overview of the mechanisms of neuroplasticity, discusses the principles of experience-dependent plasticity, and explores the connection between neuroplasticity and motor learning.

Mechanisms of Neuroplasticity

"Neuroplasticity denotes the inherent ability of the brain to adapt with macro-scale changes in response to altered environmental demands. Within this framework, plasticity is an adaptive process triggered by a prolonged mismatch between the functional supply the brain can momentarily provide and the experienced demands the environment currently poses ..." - Wenger and Kühn (2021)

The scientific and medical communities have recognised neuroplasticity's transformative potential, leading to a paradigm shift in neurorehabilitation that focuses on harnessing the brain's ability to reorganise for functional recovery. This can be seen in patients recovering from neurological conditions such as cerebral vascular accident (CVA, stroke), Parkinson's (PD), and spinal cord injury (SCI). There are various mechanisms that drive plasticity. Understanding the different forms of plasticity can be beneficial when selecting therapeutic interventions for a specific diagnosis.

Synaptic Plasticity

Synaptic plasticity is the ability of synapses, the connections between neurons, to strengthen or weaken over time in response to increases or decreases in their activity. This phenomenon is crucial for various brain functions, including learning and memory, and allows the brain to adapt based on experiences and environmental changes. There are two important mechanisms for synaptic plasticity.

1. Long-term potentiation (LTP): occurs when a synapse is repeatedly stimulated, resulting in a sustained increase in the strength of the synaptic response. This means that the postsynaptic neuron becomes more responsive to the neurotransmitter released by the presynaptic neuron.
2. Long-term depression (LTD): the counterpart to LTP. LTD involves a long-lasting decrease in synaptic strength, usually resulting from low-frequency stimulation of the presynaptic neuron. It helps refine and prune synaptic connections, allowing the brain to adapt and reorganise itself by eliminating weaker synapses.

Structural Plasticity

Structural plasticity refers to the brain's ability to change its physical structure in response to experiences, learning, and environmental demands. Unlike synaptic plasticity, which involves changes in the strength of existing synaptic connections, structural plasticity involves the growth and reorganisation of neural circuits, including the formation and elimination of synapses, dendrites, and even entire neurons.

Structural plasticity is vital for cognitive functions, including learning, memory, and recovery from neurological injuries. It enables the central nervous system (CNS) to adapt to new experiences and environments by physically reshaping its architecture. This form of plasticity has significant implications for rehabilitation strategies following neurological injuries and for developing treatments for cognitive disorders. Enhancing structural plasticity could lead to improved recovery outcomes and better cognitive performance. Key components of structural plasticity include the following.

• Dendritic growth and remodelling: the growth of new dendritic branches allows for more synaptic connections and enhances the capacity for information processing. Learning and memory have been shown to induce dendritic remodelling - i.e. dendrites can become more complex in response to new experiences, reflecting increased synaptic connections.
• Synaptogenesis: the process of forming new synapses between neurons. Synaptogenesis occurs during learning and development, allowing the brain to establish new pathways for communication. It can be influenced by various factors, including enriched environments, physical exercise, and exposure to novel stimuli.
• Synaptic pruning: the elimination of weaker or unnecessary synapses. This process is crucial for refining neural circuits and is particularly prominent during critical periods of development, such as childhood and adolescence. Pruning helps maintain the efficiency of neural pathways by reducing excess connections and focusing resources on the most relevant pathways.
• Neurogenesis: the formation of new neurons. In specific brain regions, like the hippocampus, new neurons can be generated throughout adulthood. These new neurons can integrate into existing circuits, enhancing learning and memory capabilities.
• Axonal growth and regeneration: a response to neural damage that allows for the potential regeneration of axons after a neurological injury. While this ability is limited in humans, it can help restore lost functions after brain injury or stroke.

Functional Plasticity

Functional plasticity refers to the brain's ability to adapt and reorganise its functions in response to changes in activity, experience, or injury. This process allows different areas of the brain to take on new roles or compensate for lost functions, thereby maintaining cognitive and physical abilities.

Understanding functional plasticity is important in developing effective rehabilitation strategies after brain injuries. Therapies can be designed to encourage the brain to reorganise and compensate for lost functions, using methods like targeted exercises or cognitive training. Functional plasticity also plays a vital role in learning new information and skills. It underlines the importance of practice and engagement in enhancing cognitive abilities. There are two main mechanisms of functional plasticity.

1. Neural network adaptation: when one area of the brain is less active, neighbouring regions can become more engaged, adapting to support the lost functions. This involves strengthening existing connections and forming new ones.
2. Compensatory strategies: the brain may develop alternative pathways to achieve specific tasks. For instance, if a motor function is impaired, other areas might become more active to help compensate for that loss.

Experience-Dependent Plasticity

Experience-dependent plasticity is the process by which synaptic connections are strengthened or weakened in response to specific experiences. Unlike other forms of plasticity that may be more innate or developmental, experience-dependent plasticity is directly influenced by an individual's unique interactions with their environment.

Experience-dependent plasticity is vital in recovery from brain injuries or strokes. Rehabilitation therapies can be designed to harness this plasticity by engaging patients in targeted exercises that promote the reorganisation of neural pathways and recovery of lost functions. There are two main mechanisms behind experience-dependent plasticity.

1. Synaptic strengthening: repeated exposure to certain stimuli or tasks can enhance the synaptic connections associated with those experiences. For example, practising a musical instrument leads to increased connectivity in brain regions involved in auditory processing and motor control.
2. Synaptic pruning: experiences can also lead to the elimination of unused or less efficient synaptic connections. This process helps refine neural circuits, making them more efficient by focusing resources on the most relevant connections.

Principles of Experience-Dependent Plasticity

A landmark article published by Kleim and Jones in 2008 outlines ten principles of experience-dependent plasticity. This list is based off decades of neuroscience research on how the brain learns and recovers following neurological injury. Understanding these principles can help rehabilitation professionals create more effective care plans that leverage the brain’s capacity for experience-dependent plasticity, ultimately leading to better patient outcomes.

"Neural plasticity is believed to be the basis for both learning in the intact brain and relearning in the damaged brain that occurs through physical rehabilitation." - Kleim and Jones (2008)

Below are the ten principles outlined in the Kleim and Jones article with a clinical example for each application.

1. Use it or lose it: neural circuits that are not actively engaged can weaken or disappear over time. Encouraging regular use of affected areas is crucial for maintaining function.
   • Clinical example: a patient status post-cerebral vascular accident (CVA) presents with weakness in one arm. If the patient does not utilise the affected arm, the neural pathways associated with movement will weaken. As the treating therapist, encouraging regular use of the affected arm through activities like reaching for objects or engaging in simple tasks will help maintain and strengthen those pathways.
2. Use it and improve it: engaging in targeted activities can enhance specific neural circuits. Focus on tasks that challenge and stimulate the desired movement patterns or skills.
   • Clinical example: for a patient whose goals include improving balance, activities like single leg stance, using a balance board, or standing on unstable surfaces during other therapeutic activities can specifically target the neural circuits responsible for balance.
3. Specificity: the type of training must match or directly encourage the desired outcome.
   • Clinical example: for a patient status post-knee injury with limited range of motion and strength, exercises should focus on specific movements like incremental squatting range of motion or stair climbing, rather than generic strength training. This targeted approach ensures that the therapy directly addresses the movements the patient needs to perform in daily life.
4. Repetition matters: repetitive practice is essential for strengthening synaptic connections. More repetitions lead to greater improvements in function. Research is still unclear about the number of repetitions of a specific activity needed for neural change, but it is likely in the hundreds of thousands to millions.
   1. Clinical example: for patients who present with impaired walking ability after a CVA, treatment plans should include gait training to reinforce the neural connections needed for walking. Higher repetitions of these specific movements will help solidify the learning process; it is appropriate to focus entire sessions on gait training to get the high numbers of repetitions needed for neural change.
5. Intensity matters: higher intensity training can lead to more significant neural changes. Ensure that rehabilitation exercises are challenging enough to drive improvements.
   • Clinical example: a patient with Parkinson's would benefit from high-intensity exercises, such as the high-intensity and high-amplitude exercises that are part of an LSVT BIG programme. This style of exercise can stimulate greater neuroplastic changes compared to lower-intensity activities. Monitoring and adjusting the intensity of exercises can lead to improved outcomes.
6. Time matters: the timing of interventions is important. Engaging in therapy shortly after an injury can maximise recovery potential due to heightened plasticity.
   • Clinical example: for a patient who has recently experienced a spinal cord injury, initiating rehabilitation as soon as medically feasible can capitalise on the brain’s heightened plasticity. Early intervention with focused exercises may improve recovery and functional independence.
7. Salience matters: the activity must be meaningful to the patient. Incorporating interests or real-life tasks can increase motivation and engagement, enhancing learning.
   • Clinical example: if a patient is a musician, incorporating music into rehabilitation exercises (like using rhythm to improve coordination) can increase motivation and engagement. Making exercises relevant and meaningful helps enhance the learning experience.
8. Age matters: the capacity for neuroplasticity changes with age. Younger individuals often have greater plasticity, so interventions should be tailored accordingly. This is not to say that older adults lack neuroplasticity, but they will need adaptions, such as more time or repetitions to achieve lasting results.
   • Clinical example: in older adults recovering from a hip fracture, the approach may differ from that for younger patients. While younger patients may quickly regain function, older adults may require more time and tailored strategies to promote neuroplastic changes. Activities might focus on safe ambulation and strength building to support overall mobility.
9. Transference: learning in one area can influence performance in another. Skills developed in therapy can transfer to everyday activities, reinforcing overall functional improvement.
   • Clinical example: a patient practising fine motor skills, such as grasping objects, can transfer those skills to everyday tasks like buttoning a shirt or using utensils. Demonstrating how skills learned in therapy can apply to daily life reinforces their importance and encourages practice outside of sessions.
10. Interference: new learning can interfere with previously established patterns. Be mindful of introducing new techniques that might disrupt a patient’s current progress.
    • Clinical example: if a patient has developed a limp as a compensatory movement strategy after an ankle injury, careful consideration should be given before introducing new gait training techniques to avoid reinforcing the limp. Gradual adjustments and consistent feedback are key to preventing interference with established skills.

The Active Ingredients of Neuroplasticity

A 2015 publication by Winstein and Kay looked more closely at the ten principles of experience-dependent plasticity and identified the "four active ingredients of neuroplasticity" that should be incorporated into treatment plans to optimise a patient's outcome. These principles are (1) intensity, (2) salience, (3) repetition, and (4) specificity.

Neuroplasticity and Motor Learning

Motor learning is the process of acquiring and modifying movement patterns over time through practice and experience. The acquisition and long-term retention of motor skills are crucial for everyday activities, such as writing and playing sports, and serve as the basis of rehabilitation interventions.

Recent advancements in neuroimaging and non-invasive brain stimulation have enhanced our understanding of the brain mechanisms behind motor learning. Studies on both humans and animals have revealed that the development of motor skills is linked to neuroplasticity in various interconnected brain regions, with different phases of learning engaging distinct neuronal circuits. There is growing evidence that exercise provides neuroprotective benefits that help defend against age-related mental decline and neurodegenerative diseases including Parkinson's and Alzheimer's disease. It also supports motor and cognitive recovery following central nervous system injuries. For example, aerobic exercise interventions like exergaming and treadmill gait training significantly enhance neuroplasticity by promoting cortical remapping and altering motor-related brain connectivity patterns.

Neuroplasticity is an underlying force of motor learning, and motor learning drives neuroplasticity. Please read this article to learn more about Motor Control and Motor Learning.

The OPTIMAL Theory of motor learning posits that optimal learning and performance are achieved through specific conditions that enhance motivation and promote neuroplasticity. The OPTIMAL Theory underscores the importance of motivational and contextual factors in driving neuroplastic changes during motor learning, ultimately enhancing the effectiveness of skill acquisition and retention. The OPTIMAL Theory relates to neuroplasticity in the following ways.

• Enhanced motivation: the OPTIMAL Theory suggests that fostering intrinsic motivation leads to more effective practice. When learners are motivated, they engage more deeply with tasks, which can enhance neuroplastic changes as their brains adapt to the demands of the activity.
• Feedback mechanisms: the OPTIMAL Theory emphasises the importance of effective feedback in learning. Positive feedback and specific guidance can encourage learners to refine their movements, leading to more significant neural adaptations as they practice and correct their techniques.
• Task involvement: engaging in meaningful, context-rich tasks can stimulate brain areas involved in motor control. This task-oriented approach enhances the development of neural circuits related to the specific skills being practised, promoting neuroplastic changes.
• Consolidation and retention: the OPTIMAL theory acknowledges that optimal practice conditions not only support immediate performance improvements, but also facilitate the consolidation of motor skills into long-term memory. This consolidation process is closely tied to neuroplasticity, as it involves structural and functional changes in the brain that stabilise learned skills.

Please read this article to learn more about the OPTIMAL Theory of motor learning.

Additional Resources

Optional Recommended Reading

• Kleim JA, Jones TA. Principles of experience-dependent neural plasticity: implications for rehabilitation after brain damage.
• Winstein CJ, Kay DB. Translating the science into practice: shaping rehabilitation practice to enhance recovery after brain damage. Progress in brain research. 2015 Jan 1;218:331-60.
• Wulf G, Lewthwaite R. Optimizing performance through intrinsic motivation and attention for learning: The OPTIMAL theory of motor learning. Psychonomic bulletin & review. 2016 Oct;23:1382-414.

Optional Videos

• The following TED Talk video presents a clinical example of neuroplasticity in rehabilitation practice from occupational therapist, Dr. Shawn Phipps:

• The following podcast is an interview with authors and researchers Gaby Wulf and Rebecca Lewthwaite on the OPTIMAL theory of motor learning: