Abstract
Objective: Perception of time as well as rhythm in musical structures rely on complex brain mechanisms and require an extended network of multiple neural sources. They are therefore sensitive to impairment. Several psychophysical studies have shown that patients with Parkinson's disease (PD) have deficits in perceiving time and rhythms due to a malfunction of the basal ganglia (BG) network.Method: In this study we investigated the time perception of PD patients during music perception by assessing their just noticeable difference (JND) in the time perception of a complex musical Gestalt. We applied a temporal discrimination task using a short melody with a clear beat-based rhythm. Among the subjects, 26 patients under L-Dopa administration and 21 age-matched controls had to detect an artificially delayed time interval in the range between 80 and 300 ms in the middle of the musical period. We analyzed the data by (a) calculating the detection threshold directly, (b) by extrapolating the JNDs, (c) relating it to musical expertise.Results: Patients differed from controls in the detection of time-intervals between 220 and 300 ms (*p = 0.0200, n = 47). Furthermore, this deficit depended on the severity of the disease (*p = 0.0452; n = 47). Surprisingly, PD patients did not show any deficit of their JND compared to healthy controls, although the results showed a trend (*p = 0.0565, n = 40). Furthermore, no significant difference of the JND was found according to the severity of the disease. Additionally, musically trained persons seemed to have lower thresholds in detecting deviations in time and syntactic structures of music (*p = 0.0343, n = 39).Conclusion: As an explanation of these results, we would like to propose the hypothesis of a time-syntax-congruency in music perception suggesting that processing of time and rhythm is a Gestalt process and that cortical areas involved in processing of musical syntax may compensate for impaired BG circuits that are responsible for time processing and rhythm perception. This mechanism may emerge more strongly as the deficits in time processing and rhythm perception progress. Furthermore, we presume that top-down-bottom-up-processes interfere additionally and interact in this context of compensation.
Highlights
Parkinson’s disease (PD) is a movement disorder of neurodegenerative nature affecting the basal ganglia (BG), the nigrostriatal system
Extending the work of Grahn, who primarily conducted psychophysical experiments based on rhythm perception in PD patients, we argue that the processing of musical syntax plays an important role in the processing of temporal structures in general when time is considered explicitly as a parameter in a musical context of perception
The present study shows that PD patients are impaired in their ability to discriminate temporal deviations in music perception compared to healthy controls
Summary
Parkinson’s disease (PD) is a movement disorder of neurodegenerative nature affecting the basal ganglia (BG), the nigrostriatal system. Non-motor symptoms of PD should not be neglected when considering their substantial impact on the patients’ daily lives (Todorova et al, 2014). These symptoms, such as chronic pain, depression, anxiety, cognitive dysfunction or autonomic disorders often have to be treated separately and turn out to be an additional challenge in long-term therapy (Chaudhuri and Schapira, 2009). Guehl et al who conducted psychophysical tests on 18 PD patients with deep brain stimulation in the STN concluded that the deficits in temporal discrimination reflect an “impairment in memory and/or attention rather than in the perception of time per se” Guehl et al who conducted psychophysical tests on 18 PD patients with deep brain stimulation in the STN concluded that the deficits in temporal discrimination reflect an “impairment in memory and/or attention rather than in the perception of time per se” (Guehl et al, 2008, p. 1)
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