Abstract
Problem
Recurrent laryngeal nerve injury remains a dominant clinical issue in laryngology. To date, no animal model of laryngeal reinnervation has offered an outcome measure that can reflect the degree of recovery based on vocal function. We present an avian model system for studying recovery of learned vocalizations following nerve injury.
Methods
Digital recordings of bird song were made from 11 adult male zebra finches; 9 underwent bilateral crushing of the nerve supplying the vocal organ, and two birds underwent sham surgery. Song from all birds was then recorded regularly and analyzed based on temporal and spectral characteristics using computer software. Indices were calculated to indicate the degree of similarity between pre-operative and post-operative song.
Results
Nerve crush caused audible differences in song quality and significant drops (p<0.05) in measured spectral and, to a lesser degree, temporal indices. Spectral indices recovered significantly (mean=43.0%; SD=40.7; p<0.02), and there was an insignificant trend towards recovery of temporal index (mean=28.0%; SD=41.4; p=0.0771). In 5/9(56%) birds, there was a greater than 50% recovery of spectral indices within a four week period. Two birds exhibited substantially less recovery of spectral indices, and two had a persistent decline in spectral indices. Recovery of temporal index was highly variable as well, ranging from persistent further declines of 45.1% to recovery of 87.0%. Neither sham bird exhibited significant (p>0.05) differences in song following nerve crush.
Conclusion
The songbird model system allows functional analysis of learned vocalization following surgical damage to vocal nerves.
Significance
The zebra finch provides an animal model for the study of phonatory function following neurolaryngeal injury.
Support
This project was supported by NIH grant T32DC000018.
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