Brain in Harmony: The Role of Music in Rehabilitation of People with Multiple Sclerosis

 Imagine you are running a marathon. You are on your last mile, struggling to keep a steady pace as your body starts to feel the exhaustion from a prolonged exertion of energy. You try your best to keep up with the person in front of you, but it is not enough. Instead, you choose to focus on the music playing on someone's speaker nearby. The strong beat influences you to synchronize with the music, matching each stride to the beat, creating a steady running pace. Focusing solely on the synchronization of your running to the music, a wave of energy fills your body and melts away the exhaustion you were feeling earlier. Before you know it, the last mile flies by and you cross the finish line, coming back to your body. 

This instinctive synchronization shows the impact of music on neurological and physical functioning. By uncovering the neurological mechanisms behind this synchronization process, clinicians can further explore possible treatment methods that utilize music to benefit individuals with multiple sclerosis (MS). Music-based interventions engage the whole brain which has the potential to facilitate neuroplastic changes and rehabilitation of people with Multiple Sclerosis (PwMS) through rhythmic neural entrainment.

Why Use Music?

Each musical element has a unique role within the music as well as in the individual that is engaging with it. These elements include melody, rhythm, tempo, dynamics, timbre, and instrumentation and together, they create a conclusive piece of music. However, when any of these elements are isolated, they may still affect the listener despite being disconnected from a holistic musical context.

Rhythm is a core element in music that creates structure through the organization of sound patterns [1]. Similar to its role in a piece of music, rhythm also serves as an organizational stimulus to the listener, as seen in the hypothetical example that opens this article. By adding rhythm to movement, a consistent and repetitive pattern is established to form a potential reciprocal relationship between the stimulus and physical response. In rehabilitation of people with neurological conditions, the consistency of movement may be crucial to obtaining strong neural connections and improvement in motor impairments. 

This utilization of rhythm in rehabilitation is seen in an established method of music therapy called neurological music therapy (NMT). NMT is a standardized system of clinical techniques that use the functional properties of music to train and retrain brain and behavior functioning [2]. This set of clinical techniques has shown to be effective in the rehabilitation of people with neurological conditions [1]. However, since the music therapy field is still growing in clinical practice and research, more evidence-based research is needed on this specific approach in order to further support these claims. 

Numerous studies have used music-based interventions that are similar to NMT in rehabilitation of PwMS Conklyn et al. (2010) used a technique called rhythmic auditory stimulation (RAS) to improve gait parameters in PwMS. Participants were randomly divided into a treatment group (engaged in intervention for 4-week period) and control group (engaged in intervention for 2-week period). The study involved participants walking to music with a strong beat, that was set weekly by a music therapist, to match over 10% of their baseline walking cadence. The researchers used two tests to measure the participants’ performance: GAITRite and Timed 25-Foot Walk Test (T25WT). Gait parameters such as double support, cadence, stride length, velocity, and step length were measured. The results of this study showed that all gait parameters were slightly more improved in the treatment group. Additionally, they inferred that RAS may influence the brain’s oscillator and timekeeper functions that regulate gait and that the positive results may have been influenced by enhanced motivation from the music. Overall, the researchers concluded that using an RAS-based walking program has the potential to be an effective approach to treating gait impairments in PwMS [3].

Similar studies have been conducted in which participants are instructed to synchronize with a given beat or music with a strong beat [4, 5, 6, 7, 10, 11, 12, 13, 14, 16]. In all of these studies, similar results have been reached, improving gait parameters and other aspects such as motivation, mood, and overall perceived quality of life (QoL). However the studies range in diagnoses, including individuals with Parkinson’s Disease, MS, or stroke. This variety in participants is favorable to the generalization of this treatment, however it detracts from the specificity of the results, meaning that more research in each diagnosis is needed. 

What is Multiple Sclerosis?

Multiple Sclerosis is a common neurodegenerative condition diagnosed in an estimated 2.8 million people worldwide, that would benefit from the effects of music on motor impairments [15]. MS is primarily characterized by its autoimmune nature resulting from self-targeted attack that involves the loss of physical and/or cognitive function, originating from a process known as demyelination. Neurons in the brain are wrapped with a fatty substance called myelin, which aids in neuron-to-neuron communication. In the brains of patients with MS, immune cells attack this myelin covering through the demyelination process, and broadly interfere with communication within the nervous system. Demyelination leads to insufficient signalling between neurons, causing impairments in physical and/or cognitive functioning, depending on where the damage is localized in the nervous system. 

Clinically, MS symptoms may include motor disability (such as challenges with gait), sensory disturbances, visual dysfunction, neuropsychiatric symptoms, and cognitive impairment [2]. Due to the degeneration of neural matter across the central nervous system, the strength and number of connections in the brain is significantly decreased, causing the previously mentioned impairments [3]. Given this wide variety of symptoms, the condition presents itself in many ways for each individual. Keeping this in mind, treatment methods will also need to be unique to the individual. Since the pathology of this disease is not yet clear, the current treatment methods are not equipped to cure or stop disease progression. 

Common treatments include the use of pharmaceutical drugs such as chemotherapy and anti-inflammatory treatments. These medications are often accompanied by a form of physical therapy customized to the individual [4]. Although these treatments address the physical symptoms of this condition, they do not address the cognitive and emotional aspects of  this diagnosis. However, all of these can be addressed with music [3]. Using music in treatment can be very beneficial, as it treats the individual on a holistic level, addressing all aspects of the condition.

Where is Music Processed?

In order to better understand the vastness of the neural connections that are induced by the use of music interventions, we need to address the areas in the brain that are influenced by music and where it is processed. Studies have shown interhemispheric activation in the auditory, sensory, and motor areas of the brain in response to music. The most commonly activated were the supplementary motor area (SMA), which was involved during tapping and anticipation of the beat, and the premotor cortex (PMC), involved in listening and tapping with anticipation of the beat, movement synchronization, and recognizing the metric structure of the beat [11,12,13,14,16]. Additionally, the cerebellum was shown to have a role in integrating sensory and motor information for precise motor control [11,17] and showed consistent interconnections with the left somatosensory cortex [14]. 

Additionally, music also provides motivation and less fatigue by interacting with the limbic system, activating the dopaminergic mesolimbic pathways, reward circuit pathways, and ventral tegmental area [18,17]. These interactions exhibit some of the cognitive and mood changes during treatment as they induce an increased production of dopamine. It is known that listening to music has many benefits such as increasing mood, relaxation, motivation, attention, and facilitating other cognitive functions such as memory or learning a new task. Although these effects are not the main goal of rehabilitation, they aid in the rehabilitation process by allowing the patient to stay motivated, attentive, and have an overall better perceived QoL [16,7].

In addition to activation in the central nervous system, music induces activity outside of the brain in the peripheral nervous system. Auditory-motor coupling is seen to activate the reticulo-spinal pathways, cortico-spinal pathways, and central pattern generators [17]. These pathways are found running through the spinal cord, connecting the brain with nerves that are responsible for contracting muscles to induce a movement. Specifically, the reticulo-spinal tract plays a role in coordination and pattern of movement, through the excitation of spinal motor neurons by repetitive rhythmic sound patterns [18]. This exhibits both feedforward and feedback interactions, which means that the brain and body interact through a cycle of signals that mediate the appropriate movements. After an auditory stimulus enters the brain, signals descend from the brain through the spinal tract to elicit a motor response. Signals from the muscle movements in the body are then sent back through the spinal tract to the brain for further processing, resulting in the refining of future movements. The broader effects of this processing involves mechanisms such as the neural-muscular periphery, intraspinal nervous system, and central networks for motor control and timing, such as the basal ganglia [19]. These results are notable because they show that music has the ability to not only access neural systems in the brain, but also the networks outside of the brain that are responsible for directly influencing bodily functions. Strengthening the brain-to-body connections in both areas of the nervous system is crucial to improving overall functioning, especially in individuals lacking sufficient connections between these networks.

Communication between music and the brain

Music interacts with the brain on a cellular level, organizing neural changes and movement through a process called rhythmic entrainment. Rhythmic entrainment is mediated by phase-locking, which involves the synchronization of neural frequencies to a rhythmic stimulus, creating a stable firing pattern of neural networks [2]. Overall, the phase-locking process results from the synchronization of neural networks that cause the motor responses to lock with the rhythmic stimulus pattern. Given these effects, it can be suggested that rhythmic entrainment is a mechanism behind using music-based interventions for physical and cognitive rehabilitation of individuals with neurological conditions including MS [9, 6, 5, 4, 8, 10]. 

The amplitude of the neural frequency responses are measured in the brain through steady-state evoked potentials (SSEPs: oscillatory activity where neural frequencies are locked to the beat frequency). Amplitude refers to the power of the signal, depending on the electrical potential and the amount of neurons involved in the connection. Studies have shown that using an auditory stimulus with a specific frequency will elicit an SSEP response (measured in Hz) that is associated with specific functions during the entrainment process [18, 19, 20]. The 2.4 Hz SSEP is associated with beat-related entrainment, which refers to the excitation of neurons involved in synchronizing their frequencies with a given rhythmic stimulus. Similarly, the 1.2 Hz SSEP is associated with movement-related entrainment, referring to the excitation of neurons involved in synchronizing the movement to the rhythmic stimulus. Lastly, the 3.6 Hz SSEP corresponds to the sum of the beat and movement frequencies, suggesting a cross-modulation product of sensorimotor integration [5, 6, 7]. These findings show that, by using a specific type of music, the clinician has the ability to engage the brain in specific processes in order to achieve consistent neural and physical responses. 

Another helpful process in using an auditory stimulus to induce neural communication between systems is called priming. Priming is a process in which auditory-motor entrainment in one effector system may “prime” another system, so that less neural activity will be needed when performing a similar task later [8, 2]. This interconnectivity between systems may explain why listening to an auditory stimulus facilitates a steady synchronization. As mentioned before, by having repetitive movements and neural signalling, connections between neural networks may be strengthened. Therefore, it may be beneficial to prime the brain in rehabilitation before moving to a stimulus in order to create pre-established connections before activating another neural system [2]. Researchers have stated that rhythmicity of brainwaves in the motor cortex may also modulate brainwaves in the auditory cortex, which then influence auditory perceptual processes later, creating less effort for brainwaves to synchronize to the auditory stimulus [2]. Given this finding, using music in rehabilitation engages different systems in the brain, allowing patients to form neural connections before even starting the main rehabilitation activity. This is important in neurodegenerative disease treatment, because forming new connections between different neural systems may compensate for the loss of other functions, potentially resulting in rehabilitation of lost connections. Since clinicians have not directly linked this concept to MS, more research is needed on this subject in order to better understand how it relates to specific characteristics of this condition. 

One exciting possibility is that the induced structural and organizational changes from recovery-oriented interventions (such as music-based interventions) may be a result of activity-dependent remyelination [9]. These effects are essential in the treatment of PwMS (Persons with Multiple Sclerosis), as their neurons lack myelin, causing signaling deficiencies and neuronal death. Activity-dependent remyelination is considered as the myelination process that is dependent and/or regulated by electrical neuronal activity [20]. The consistent rhythmic nature of music-based interventions is likely to help in the improvement of physical symptoms, as the more repetition of electrical neuronal activity there is in a specific network, the stronger the connections will get. Using rhythm to provide this structure and stimulation to the CNS may benefit these individuals in the long-term as it may be linked to remyelination of neurons over time.

What does this mean for people with Multiple Sclerosis?

Given these findings, we can conclude that using music is an effective way to interact with an individual on a functional and psychological level. Studies using music-based interventions for rehabilitation in PwMS have shown improvements in walking, in terms of speed, stride length [3], double support, gait cadence, velocity [9] and balance. Additionally, it has also shown improved psychological states such as mood, motivation, perceived QoL, and a decrease in overall fatigue [3,16]. These results demonstrate the holistic nature of this treatment, as it facilitates multisensory integration for motor stabilization and control [19], provides musical agency for higher motivation, and lessens fatigue [16]. More specifically, our understanding of rhythmic entrainment as a mechanism behind physiological rehabilitation will help researchers and clinicians refine their practice to address specific needs of individuals. The consistency from a rhythmic auditory stimulus is necessary in facilitating stronger connections between the brain and body, leading to a physiological and psychological healing process. As seen in the physical and psychological effects of using a music-based treatment, the instinctive rhythmic nature of our nervous system can be used to our benefit as a method of reorganizing brain and body connections. 

Through the review of the available literature, we can conclude that approaching treatment from a holistic level is attainable through music. Although there is limited research that mentions rhythmic entrainment as a mechanism behind rehabilitation in PwMS, using a music-based method has shown promising effects in other neurodegenerative conditions, and has the potential to be generalized to MS. Ultimately, the opportunity to customize music towards each individuals’ preference, contributes to their personal emotional experience and motivation during the treatment. By reviewing the results of brain responses, we can further understand the potential of using music in rehabilitation on a cellular level. This underlying evidence of plasticity supports the pursuit of more effective and enjoyable treatments for PwMS, and similar conditions. 

Conclusion

Although this article focuses on PwMS, music-based interventions are useful with other neurological disorders such as Parkinson’s, stroke, Alzhiemer’s, and traumatic brain injury. More literature is available for conditions such as Parkinson’s and stroke, therefore, it should be made aware of the need for research for MS specifically. The similarity between all of these conditions is their neurodegenerative pathology, which may open similar treatment opportunities for each. Since these conditions also have common symptoms with MS, it is possible that music can access these impairments on a neurological level as seen in PwMS.

This research is not without limitations, as there is a notable lack of literature regarding using music in a rehabilitation setting. As research in this field continues, our understanding behind the mechanisms of rehabilitation will allow us to further refine our treatment methods through an evidence-based practice. Additionally, collaborating with neuroscientists to further understand the neural processes involved specifically in the NMT approach will allow music therapists to further refine their methods. Moving forward, keeping in mind the individual’s personal abilities and preferences will lead us to a treatment that is effective, meaningful, and treats the individual in a humanistic way.

In summary, using music-based interventions for PwMS is an effective, personalizable, and holistic way to address gait impairments and psychological aspects such as mood, motivation, and perceived QoL. Given the findings from the available literature, music has the ability to access a widespread variety of regions in the brain, interact through connections in the body, and improve other psychological aspects through the limbic system. As we continue to explore using music in rehabilitation, potential approaches may be refined to further benefit the individual as well as open doors to other populations.

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