Music Therapy Interventions in Parkinson’s Disease: The State-of-the-Art

Parkinson’s disease (PD) is a neurological disorder involving the progressive degeneration of the dopaminergic system, which gives rise to movement-related dysfunctions (such as bradykinesia, tremor, and rigidity) as well as other symptoms, mainly of cognitive and psychological nature. In the latter case, mood disorders prevails frequently causing anxiety and depression in all phases of the disease, sometimes even before the motor symptoms occur. Aarsland and colleagues (1) report that 35% of the patients affected by PD present depression, whereas Richard (2) states that anxiety is to be found in 40% of the cases. The literature shows that playing and listening to music may modulate emotions, behaviors, movements, communication, and cognitive factors,modifying the activity of the brain areas involved in the perception and regulation of these aspects (3, 4). Music can produce substantial effects on movement-related symptoms as well as psychological ones in PD treatment. Concerning the first aspect, rhythm has a crucial role in rehabilitation, enhancing connections between the motor and auditory systems (5). Literature showed how a rhythmic auditory cues-based training can produce a compensation of the cerebello-thalamo-cortical network leading to beneficial effects, for example, improving not only speed and step length but also perceptual and motor timing abilities (6, 7). Areas involving rhythm perception are closely related to those that regulate movement (such as the premotor cortex, supplementarymotor area, cerebellum, and basal ganglia – especially putamen) (8–18). A study conducted with fMRI (19) shows that whereas a regular pulse (in contrast to an irregular one) generally activates basal ganglia in a significant way, this is not the case in PD. Other studies (7, 20) support the idea that external cues (in particular rhythmical cues) can modulate the activity within the impaired timing system. This may mean that a regular rhythmic pulse stimulates the putamen activity, facilitating movement and providing an input for sequential movements and impaired automatized processes. Moreover, this could compensate for the lack of dopaminergic stimulation. Rhythm can be also perceived visually and through the tactile sense, but the reaction time of the human auditory system is shorter by 20–50ms, when compared to visual and tactile stimuli; moreover, it has a stronger capacity of perceiving rhythm periodicity and structure (6). Therefore, rhythm influences the kinetic system (through synchronization and adjustment of muscles to auditory stimuli), facilitates movement synchronization, coordination, and regularization, and may even produce an internal rhythm that persists in the absence of stimuli (21–23). Many studies report that musical rhythm in PD treatment can improve gait (speed, frequency, and step length), limbs coordination, postural control, and balance (7, 18, 24–36). In view of the above, Neurologic Music Therapy (NMT) – especially Rhythmic Auditory Stimulation, one of its techniques – characterizes this approach to the disease: NMT aims at enhancing sensory, cognitive, andmotor functions (as in PD treatment, in which specific rhythmic techniques can strengthen and improve the rehabilitative process).