Thaut, M. H. (2013). Entrainment and the motor system. Music Therapy Perspectives 31, 31-34.
Auditory rhythmic patterns can facilitate entrainment of movement in patients with motor disorders. The auditory system is adept at detecting temporal patterns in auditory signals, operating with greater speed and precision than visual or tactile systems. Extensive fibre connections exist between the auditory system and cortical and subcortical motor centres, as well as the brain stem and spinal cord. When an auditory rhythmic stimulus triggers auditory neurons to fire, motor neurons driving the motor system also fire and entrain in response. This auditory stimulation primes the motor system into a state of readiness, enhancing subsequent response quality. Consistent rhythmic stimuli provide a stable template onto which movement can be mapped. Anticipation is critical in improving quality of movement. When provided with precise timing cues, the brain can plan, knowing how much time has elapsed and how much time is left, allowing it to scale velocity and acceleration according to the constraints of the rhythmic template. This allows for optimization of movement quality, enhancing overall motor control with respect to space, time and force, There is less variability in trajectory, resulting in smoother movement as a result of more efficient muscle recruitment.
Rhythmic entrainment is an important mechanism in the rehabilitation of motor disorders due to a variety of neurological conditions. Functional control of movement can be improved through practice using the principles of motor entrainment. Substantial gains in gait patterns have been noted with hemiparetic clients, showing improvements in velocity, stride length, cadence, and stride symmetry as a result of the application of entrainment mechanisms. At the same time there have been significant reductions in variability and amplitude of muscle activation. As a result, a protocol has been developed called Rhythmic Auditory Stimulation (RAS) to facilitate improvement in gait due to entrainment effects. Persons with Parkinson’s Disease have demonstrated improvements in bradykinesia, stride length stability and symmetry due to RAS, resulting in long-term improvements in ambulation. Experiments involving upper extremity movement, not inherently rhythmic, have yielded comparable improvements when movement is matched to rhythmic time cues. Oral motor, articulatory control also benefits from the application of rhythmic entrainment principles, as demonstrated through the critical rhythmic component of Melodic Intonation Therapy (MIT). In addition, time structure may provide a temporal scaffold with respect to attention, memory and executive function, offering potential for improvements with respect to cognitive function.
Extensive research has been conducted with respect to gait and RAS, including several randomized controlled trials, which have substantiated the role of RAS in motor rehabilitation therapy for gait disorders. Similar research needs to be undertaken with respect to arm/hand movement, speech/language, and cognitive function. These are all areas which would benefit from randomized controlled trials to determine the extent to which auditory rhythmic stimuli facilitate functional improvements. I haven’t had the opportunity to work with clients on ambulation, but have been able to work with clients on upper extremity movement and speech/language using rhythmic cuing principles, all with promising results. To be accepted by the medical community, however, we need more than case study examples - larger scale, replicable studies need to be undertaken.
I have found the use of client preferred music and/or improvisation within a stable rhythmic framework is particularly motivating for clients. To optimize functional improvement, drawing on this affective component is critical to maximize engagement and sustain client attention. Though repetition is needed to rehabilitate movement, it can be anything but boring for the client engaged in making music that is personally meaningful. This has the added function of contributing to psychosocial wellbeing, a critical factor in any therapy program. it can be empowering for the client, helping them to regain some sense of control as they help shape the musical experience. It can also bring a sense of joy into their lives, enhancing overall quality of life. Rhythmic applications in rehabilitation hold substantial promise in supporting gains in multiple domains in addition to the quality and functionality of motor movement.