Vocal biomarkers of aging and Parkinson’s disease in a songbird
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Purpose
Similar vocal impairments occur in normative aging and Parkinson’s disease (PD), making differential diagnosis challenging in early stages. The brain’s role in age and PD-related vocal dysfunction is unclear. This motivated our use of the zebra finch songbird model. We applied human acoustic analysis to evaluate aging and parkinsonian-like birdsong for shared and distinct features.
Method
Two open-access datasets of zebra finch song were analyzed using an expanded set of parameters that, in the case of humans, can detect subtle changes in voice. The aging dataset included younger, middle aged, and older birds. The PD dataset included birds receiving viral injections into Area X to induce alpha-synuclein overexpression (ASYN) or control treatment, recorded pre- and post-injection. Songs were automatically segmented into motifs using cross-correlation. Acoustic measures were extracted from harmonic, noisy, and mixed syllables.
Results
Middle aged birds differed from younger and older birds, showing non-linear trajectories in fundamental frequency ( f o ) measures and age-related increases in spectral slope, spectral emphasis, and intensity variability, whereas temporal parameters remained stable. In PD, pre-post changes occurred in both ASYN and controls, with ASYN birds exhibiting larger effects for f o variability, decreasing frequency modulation, and vocal intensity measures.
Conclusions
Vocal aging in zebra finches was characterized by non-linear trajectories and prominent spectral and intensity-related changes. In a gene-driven PD state there were greater alterations in f o variability and intensity regulation, features that may distinguish aging- from ASYN-related vocal variability. These findings support the zebra finch as a translational model for vocal biomarkers research.
