FES encourages Neuroplasticity - and why that's a good thing.
Functional Electrical Stimulation (FES) has been a widely used technology in rehabilitation for many decades. But did you recognise how FES can contribute to neuroplasticity. Varying the nature of the stimulation and how we apply it can have many effects and be an essential tool to facilitate constructive neuroplasticity when recovering from a stroke or other neurological condition. We know now that our nervous system remains "plastic" throughout our lives, and this fact has been a great source of hope for those recovering from a neurological insult. But what is neuroplasticity, and do we understand how to leverage it? In this article, we examine this topic and examine how FES can support neuroplasticity as part of physical rehabilitation that aims to recover function following a stroke or other neurological problem.
What is Neuroplasticity anyway?
Over the past few decades, neuroscientists have debunked the long-standing belief that the adult brain is incapable of change. Neuroplasticity highlights the brain's extraordinary capacity to rewire its neural circuits and alter connections between neurons in response to good - or bad - "experience".
This experience could range from acquiring new, positive behaviours to recovering from detrimental events like a stroke. Neuroplasticity encompasses the brain's structural and functional adaptations influenced by learning, environmental factors, and biological variations. It showcases the brain's versatility in forming new neural pathways, strengthening or weakening existing connections, and sometimes transferring functions to different brain areas. This adaptability plays a pivotal role in learning, memory development, and recovery from brain injuries. (Kandel et al. 2013.)
Fascinatingly, current research indicates that physical activity can significantly boost cognitive functions, too. This suggests that our thoughts are influenced not solely by our brains but also by our physical actions. The theory of embodied cognition posits that cognitive processes are intricately linked to the body's engagement with its surroundings. This viewpoint advocates that the mind extends beyond the brain, encompassing the body's dynamic interaction with the environment. In the distant past, it was thought that the brain was somehow the " master" organ issuing commands to other organs and body parts in a hierarchical or top-down system. Now, we know it is not so simple. The brain does not issue commands so much as orchestrate "conversations" with other body parts. We could say that it is not just the brain that "thinks". We should then recognise that neuroplasticity does not just happen "in the head" - it is fundamentally about how the whole body works down to a cellular level.
In popular literature, neuroplasticity is generally considered positive, but as we have already hinted, this is not always true. Neuroplasticity can be the source of potential improvement in function if we can somehow harness it. Still, if we do nothing, we will see the body’s ‘use it or lose it’ process at work and the adaptations that result may not be beneficial.
So how do we put these concepts to work in rehabilitation?
Sometimes, people refer to a "recipe" for neuroplasticity as employing task-specific exercise that is frequently and intensively applied and ideally meaningful to the person. Suppose someone is recovering from a stroke and is looking to recover arm and hand movement. In this context, the basic idea is that if we can only practise the desired arm movement in a particular way, we might recover lost function, at least in part. They must somehow practise the required movement with sufficient quality and often enough. The flip side is that we must ‘use it or lose it’.
Neuroplasticity is Learning-Dependent
We could consider neuroplasticity as applying a controlled stimulus (for example movement training) to achieve a beneficial outcome (functional recovery). Evidence suggests that several noninvasive, clinically accessible forms of energy can be a source of useful stimulus (Robertson et al., 2006). Electrical, magnetic, and vibration stimuli may be used to implement or augment the effects of training. We are particularly enthusiastic about electrical stimulation which is generally well understood.
At its core, stimulation can trigger the same neural pathways as a typical movement. When paired with actual movement training, for example, with a stroke patient this approach can significantly enhance neuroplasticity, surpassing the levels achieved through movement practice or training alone. Research involving neurologically healthy individuals has demonstrated that these methods can boost neural excitability and improve motor skills. Non-invasive, clinically approved forms of electrical stimulation can be utilised to adjust neural excitability. This is a safe and effective supplementary treatment to programs that enhance hand/arm or walking functions in individuals with neurological conditions.
Several factors are commonly involved in motor learning and, hence, neuroplasticity. To some extent, they overlap:
Motor Learning
Just because your brain and nervous system are capable of change (e.g., Learning), this doesn't mean they will change in a useful way if left neglected. Learning generally follows the steps below.
Use it or Lose it.
The flip side of failing to drive specific brain and nervous system functions is degradation. Neuroplasticity occurs naturally in response to nervous system injury and can be maladaptive.
Use it and Improve it.
Training that drives a particular function can enhance that function. The nature of the training experience dictates the nature of the adaptation. Research shows that the task's difficulty affects the quality of the learning process (Magness, 2022). The challenge is creating a situation where practice is difficult and cognitively engaging but not impossible. Something too difficult leads to frustration, and learning will halt.
Specificity
Specificity effects have been recognised in learning research for more than 100 years. The general finding is that the transfer of skills from practice to real-world application will be small unless the skills required are nearly identical. This means that general exercise and strength training are most effective when combined with task-specific training programmes. Research is now looking at how practice in one task can transfer to another task meaningfully.
Repetition is Important
Learning always requires sufficient repetition. Without a necessary and sufficient volume of repetition, no learning can take place. The difficulty we often have is knowing just how much repetition is needed. This is also where technology can help. FES can trigger a contraction in muscles that are weak and fatigued or even denervated. Robotic systems can support movement patterns and guide weakened limbs to follow a desired path. This way more repetitions can be performed than would otherwise be possible.
Intensity matters
Sufficient training intensity is always needed. What do we mean by ‘intense’? Intensity implies that some combination of the dose, frequency, and duration of training practice is important to get results. Although research supports this suggestion, there is typically a lack of detail when we try to pinpoint the necessary and sufficient level of intensity for an individual case.
Time
Different forms of learning and plasticity occur at different times during training, which implies that the timing of an intense therapy programme is important. Some researchers advocate early interventions, for example, in the first month after a stroke. This seems to make sense, but unfortunately, for many reasons, a lot of stroke research has only been carried out in the chronic phase of recovery.
Salience is Important
The training experience must be sufficiently salient to learn. Salient information typically captures the learner's attention and is used to guide and improve motor performance and learning. This can include feedback that helps learners detect and correct errors, achieve a stable performance pattern, and develop an efficient movement representation. Some researchers point out that tapping into someone’s motivation to practise may be more effective than simply cranking up the intensity of the practice. The idea here is that focusing on practice to reduce impairment is less motivating than seeking benefits that will directly impact the person’s quality of life. Many therapeutic interventions rely on extrinsic motivation to be effective. It seems that the best results come when motivation is intrinsic, and the person’s mindset is adjusted to provide a consistent drive to improve.
Age matters
Training-induced learning takes place more readily in younger brains (oh well)
Transference
Learning acquired in one area can enhance skills acquisition in related areas.
Interference
Learning acquired after one experience can sometimes interfere with acquiring other behaviours.
Cellular Nuts and Bolts
One of the key mechanisms of neuroplasticity is called Long-Term Potentiation (LTP). LTP is essentially the process by which synaptic connections between neurons become stronger with frequent activation. This strengthening of synapses (communication points between neurons) plays a crucial role in learning and memory.
Here’s a simplified explanation of how LTP works:
Neuronal Communication: Neurons communicate with each other via synapses. One neuron sends a chemical signal to another neuron through these synapses. The neuron that sends the signal is called the presynaptic neuron, and the one that receives the signal is called the postsynaptic neuron.
Signal Transmission: When a signal is transmitted from the presynaptic neuron, it releases neurotransmitters into the synaptic cleft (the small space between the neurons). These neurotransmitters then bind to receptors on the postsynaptic neuron.
Calcium Influx: For LTP to occur, the postsynaptic neuron needs a strong and repeated signal. This strong signal causes a significant influx of calcium ions into the postsynaptic neuron. Calcium is crucial because it signals that something important is happening within the neuron.
Activation of Enzymes and Gene Expression: The calcium influx activates certain enzymes and can even influence gene expression in the neuron's nucleus, leading to changes in the neuron's structure and function.
Strengthening Synapses. These changes strengthen synapses, making the postsynaptic neuron more sensitive to future signals from the presynaptic neuron. Essentially, this enhances the connection between these neurons, making it easier for them to communicate.
Memory Formation: LTP is believed to be one of the physiological mechanisms underlying memory formation. By strengthening the synaptic connections, the brain is essentially building a network that will trigger the same response in the future when similar signals are received.
In summary, LTP is how neuroplasticity works at a cellular level to help our brains learn from experiences, form memories, and even recover from injuries. The brain's adaptability allows it to meet the challenges of normal development and damage recovery. By enhancing synaptic strength, LTP facilitates information storage within the brain, making it an essential mechanism for learning new skills or adapting to new experiences.
How does FES support Motor Learning?
Functional Electrical Stimulation (FES) aligns perfectly with motor learning and neuroplasticity principles and can play a pivotal role in rehabilitation. Motor learning involves acquiring or refining movement skills supported by the brain's neuroplastic abilities to form new neural connections. FES significantly boosts this learning process by delivering precise electrical stimulation to specific muscles or nerve fibres, thus aiding movement and enhancing the motor learning journey.
Here are some of the ways that FES aligns with the motor learning steps we presented above.
Hasomed RehaStim 2 - can generate complex stimulation sequences
Initiation of Movement: FES can initiate movement in muscles that are weak or paralysed due to neurological injuries, such as stroke or spinal cord injury. This provides an opportunity for the patient to practice movements that they perhaps cannot do unaided. This is a fundamental aspect of motor learning (Hara, 2008 and 2013).
Most FES units designed for NMES (NeuroMusclular Electrical Stimulation) can easily produce muscle contractions. These contractions should ideally be "functional" and might involve the user's intention to trigger a contraction to be effective.
Units such as the RehaStim 2 can go further and be programmed to produce a contraction based on a triggered sequence. Multiple channels of stimulation can be triggered to initiate complex limb movement patterns. When used in a RehaMove FES Cycling configuration, this stimulator delivers stimulation sequences synchronised with the movement of a passive/active bike's pedals.
Devices can use the faint EMG signal from a muscle in an affected limb or the contralateral limb to trigger muscle contraction. This has the advantage of involving the user's intention, which enhances the learning effect. We will shortly bring such a device to the UK market.
An increasing number of research teams are investigating the efficacy of brain-computer interface (BCI)-mediated interventions for promoting motor recovery following stroke. A growing body of evidence suggests that of the various BCI designs, the most effective are those that deliver functional electrical stimulation (FES) of upper extremity (UE) muscles in a method contingent on movement intent. (Remsik et al, 2022)Sensory Feedback Enhancement: The stimulation provided by FES also enhances sensory feedback by activating sensory pathways. This feedback is crucial for motor learning, allowing the brain to adjust and refine movements based on sensory input, thereby promoting neuroplasticity.
Repetition and Practice: As we have seen, motor learning requires repetition and practice. FES allows for the repetitive practice of movements, even in those with significant motor impairments. This repetition is essential for the consolidation of motor skills through neuroplastic changes. Muscle fibre changes following a neurological insult often mean that patients fatigue rapidly. FES can improve the fatigue situation over time, thereby allowing more repetitions to be performed.
Task-Specific Training: FES can be used to assist in task-specific training, which is a form of motor learning that involves practising specific tasks or movements that an individual aims to improve. By facilitating the practice of these tasks, FES can help relearn motor skills and enhance functional recovery. (Olaya, 2015)
The RehaMove/RehaStim 2 unit being used to train shoulder stabilisation post-stroke
As we discussed above, neuroplasticity is the underlying mechanism for motor learning. It involves changes in synaptic connections' strength, new connections' formation, and sometimes the creation of new neurons. FES contributes to neuroplasticity by:
Strengthening Neural Pathways: By repeatedly activating specific neural pathways, FES can strengthen these pathways, making them more efficient. This process is akin to the principles of Hebbian plasticity, where 'neurons that fire together wire together'(Hatsopoulos, 2022).
Cortical Reorganization: FES has been shown to induce cortical reorganisation, where the brain's motor cortex adapts to changes in motor demands. This reorganization is a hallmark of neuroplasticity and is crucial for recovering motor function after injury.
Enhancing Motor Recovery: The ultimate goal of tapping into neuroplasticity through motor learning is to enhance motor recovery - true restoration of function. FES, by facilitating movement and providing sensory feedback, contributes to the recovery of motor function. This is particularly evident in individuals with stroke or spinal cord injuries, where FES has been shown to improve motor outcomes.
Our Commitment to Electrical Stimulation
Anatomical Concepts is a UK leader in the clinical application of electrical stimulation and has many decades of experience whether as NMES, EMG triggered NMES, FES Cycling or ES for denervated muscle. We work with clients at home recovering from a catastrophic injury, trauma or a neurological condition and we offer a range of products for various applications including the following.
RehaMove 2 - To support our popular FES Cycling options as well as Sequence Mode software with many therapy applications
The Stim2Go product
Schuhfried Edition 5 - A very flexible and powerful two channel unit offering many stimulation protocols including those for NMES, pain relief and denervated muscle.
Schuhfried RISE stimulator - Optimised for the long term management of denervated muscle with additional protocols for innervated muscles.
Stim2Go - Coming soon. An innovative device offering FES Cycling, tSCS, neuropathic pain and much more in an easy to use App driven package
KT Motion - Coming soon. An innovative device design to support various EMG triggered FES applications.
Contact us for further information or a demonstration.
Summary
Functional Electrical Stimulation (FES) is an indispensable tool in the rehabilitation field that efficiently combines the concepts of motor learning and neuroplasticity. FES effectively initiates movements in weakened or paralysed muscles, enhances sensory feedback, encourages the repetition and practice of movements, and supports task-specific training, thereby empowering motor learning.
All these processes are rooted in the brain's ability to adapt and reorganise itself - a principle known as neuroplasticity. FES not only strengthens neural pathways and promotes cortical reorganisation but also plays a significant role in motor recovery. This method is an ideal solution for individuals recovering from neurological injuries such as strokes or spinal cord injuries, leveraging their brain's neuroplastic capabilities to restore function and improve overall motor outcomes. FES is an essential and highly recommended approach for rehabilitation professionals to ensure optimal recovery outcomes for their patients.
Related Articles
Kandel, E; Koster, J; Mack, S; Siegelbaum, S (2013) Principles of Neural Science (fifth edition). McGraw-Hill
Maugeri G, D'Agata V, Musumeci G. Role of exercise in the brain: focus on oligodendrocytes and remyelination. Neural Regen Res. 2023 Dec;18(12):2645-2646. doi: 10.4103/1673-5374.373683. PMID: 37449603; PMCID: PMC10358674.
Magness, S (2022) Do hard things: Why we get resilience wrong and the surprising science of real toughness. Harper Collins
Muhammad, Mubarak and Tasneem M. Hassan. “Cerebral Damage after Stroke: The Role of Neuroplasticity as Key for Recovery.” Cerebral and Cerebellar Cortex – Interaction and Dynamics in Health and Disease (2021): n. pag.
Bruel-Jungerman E, Davis S, Laroche S. Brain plasticity mechanisms and memory: a party of four. Neuroscientist. 2007;13:492–505.
https://pubmed.ncbi.nlm.nih.gov/17901258/
Zotey V, Andhale A, Shegekar T, Juganavar A. Adaptive Neuroplasticity in Brain Injury Recovery: Strategies and Insights. Cureus. 2023 Sep 24;15(9):e45873. doi: 10.7759/cureus.45873. PMID: 37885532; PMCID: PMC10598326.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10598326/
Müller P, Duderstadt Y, Lessmann V, Müller NG. Lactate and BDNF: Key Mediators of Exercise Induced Neuroplasticity? J Clin Med. 2020 Apr 15;9(4):1136. doi: 10.3390/jcm9041136. PMID: 32326586; PMCID: PMC7230639.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7230639/
Olaya, Andrés Felipe Ruiz et al. “Using Orientation Sensors to Control a FES System for Upper-Limb Motor Rehabilitation.” International Work-Conference on Bioinformatics and Biomedical Engineering (2018).
Popović, Dejan B. et al. “Electrical stimulation as a means for achieving recovery of function in stroke patients.” NeuroRehabilitation 25 1 (2009): 45-58 .
Wu, Fang-Chen et al. “Clinical effects of combined bilateral arm training with functional electrical stimulation in patients with stroke.” 2011 IEEE International Conference on Rehabilitation Robotics (2011): 1-7.
Hara Y. Neurorehabilitation with new functional electrical stimulation for hemiparetic upper extremity in stroke patients. J Nippon Med Sch. 2008 Feb;75(1):4-14. doi: 10.1272/jnms.75.4. PMID: 18360073.
Hara, Y. “Rehabilitation with Functional Electrical Stimulation in Stroke Patients.” International Journal of Physical Medicine and Rehabilitation 1 (2013): 1-6.
Hara Y. [Novel functional electrical stimulation for neurorehabilitation]. Brain Nerve. 2010 Feb;62(2):113-24. Japanese. PMID: 20192031.
Olaya, Andrés Felipe Ruiz et al. “Using Orientation Sensors to Control a FES System for Upper-Limb Motor Rehabilitation.” International Work-Conference on Bioinformatics and Biomedical Engineering (2018).
Olaya, Andrés Felipe Ruiz et al. “Toward an Upper-Limb Neurorehabilitation Platform Based on FES-Assisted Bilateral Movement: Decoding User's Intentionality.” International Work-Conference on the Interplay Between Natural and Artificial Computation (2015).
Hatsopoulos NG. The importance of volitional behavior in neuroplasticity. Proc Natl Acad Sci U S A. 2022 Jul 26;119(30):e2208739119. doi: 10.1073/pnas.2208739119. Epub 2022 Jul 15. PMID: 35858459; PMCID: PMC9335316.
Hasson CJ, Manczurowsky J, Collins EC, Yarossi M. Neurorehabilitation robotics: how much control should therapists have? Front Hum Neurosci. 2023 May 11;17:1179418. doi: 10.3389/fnhum.2023.1179418. PMID: 37250692; PMCID: PMC10213717.
Remsik AB, van Kan PLE, Gloe S, Gjini K, Williams L Jr, Nair V, Caldera K, Williams JC, Prabhakaran V. BCI-FES With Multimodal Feedback for Motor Recovery Poststroke. Front Hum Neurosci. 2022 Jul 6;16:725715. doi: 10.3389/fnhum.2022.725715. PMID: 35874158; PMCID: PMC9296822.