Musical stimulation with feedback in gait training for Parkinson’s disease.

Patients suffering from idiopathic Parkinson's disease (PD) are unable to steadily generate regular steps due to an impairment of the basal ganglia that do not cue the supplementary motor area properly (Iansek, Bradshaw, Phillips, Cunnington, & Morris, 1995). This results in the main hallmarks of parkinsonian gait: reduced step cadence, reduced velocity, and shortened stride length. In the 1990s the use of acoustic stimulation for the rehabilitation of gait disorders in PD was developed under the concept of rhythmic auditory stimulation (RAS). RAS consists of a clear accentuated, either metronomic or musical rhythm that stimulates the production of rhythmical movements (Thaut, 2005), especially with respect to their timing. The consistent coupling between steady tempo of the acoustic stimulation (bpm, beats per minute) and walking cadence (spm, steps per minute) of PD patients has This been systematically investigated and the effectiveness of RAS broadly attested (for reviews see Lim et al., 2005; Nombela, Hughes, Owen, & Grahn, 2013; Tomlinson et al., 2013).In the standard RAS protocol, stimulation tempo usually corresponds to baseline cadence increased by 10% (Arias & Cudeiro, 2008; Freedland et al., 2002; Hausdorff, Lownthal, Herman, Gruendlinger, Peretz, & Giladi, 2007; Willems et al., 2006). RAS exerts a direct effect upon cadence and a consequent effect upon stride length. Because stride length in PD patients is lower than in healthy people at any given velocity (Ebersbach et al., 1999), it may be beneficial for the patient to address it specifically, as an independent therapy goal.Our choice of using musical instead of metronomic stimuli follows music therapist Michael Thaut's approach, where rhythmic stimuli are embedded in a musical structure. The approach is based on findings that rhythmic patterns within a musical context reduce response variability and synchronization offset more effectively than do single-pulse pattern in the frequency range of 60 to 120 spm (Thaut et al., 1996). Moreover, it has been demonstrated that healthy subjects synchronize more precisely (i.e., with lower negative mean asynchrony) with musical rather than metronomic stimuli (Repp, 2005). In the early studies with PD patients, RAS consisted of instrumental pieces in 2/4 or 4/4 m with rhythmic on-beats enhanced by a metronome (McIntosh, Brown, Rice, & Thaut, 1997; Miller, Thaut, McIntosh, & Rice, 1996; Thaut et al., 1996), and it was suggested that, compared with metronome, musical texture provides additional timing information and may therefore facilitate detection, anticipation, and synchronization to the beat (Thaut, Rathbun, & Miller, 1997). Moreover, music facilitates emotional involvement and motivates engagement in a task, and might therefore be a more efficient stimulation than the plain metronome beat. Recently, attention to the comparison between metronomic and musical stimulation and to the specific features that would account for the effectiveness of music seems to be increasing (Buhmann, Desmet, Moens, Van Dyck, & Leman, 2016; Styns, van Noorden, Moelants, & Leman, 2007; Wittwer, Webster, & Hill, 2013). Moreover, the specific effectiveness of music-based movement therapy on PD has been investigated in a meta-analysis (de Dreu, van der Wilk, Poppe, Kwakkel, & van Wegen, 2012).The fundamental advantage of the RAS approach is that it is able to replace the impaired internal stimuli of a parkinsonian brain. However, as stimulation proceeds independently from movement execution, there is no feedback mechanism that helps evaluate movements' adequacy. The potential of concurrent sensory feedback for enhancing motor learning has been extensively studied on healthy subjects (Sigrist, Rauter, Riener, & Wolf, 2013) and an interactive, feedback-like version of RAS has been recently proposed for the training of stride time in PD patients (Hove1, Suzuki, Uchitomi, Orimo, & Miyake, 2012). …