Ultrasonic Vocalization Acoustics After Recurrent Laryngeal Nerve Injury and Recovery.

Abstract

Objectives: The lack of well-defined functional acoustic correlates of vocal fold paralysis in animal models creates challenges for translating basic science studies of recurrent laryngeal nerve (RLN) injury to patients with vocal fold paralysis. Capitalizing on natural communicative rodent ultrasonic vocalizations (USVs), this study aimed to (1) investigate the impact of RLN injury on USV acoustics in both acute and chronic stages of RLN injury and (2) to identify USV parameters with the greatest ecological validity specific to RLN injury.

Methods: USVs were recorded over 2 weeks (acute) in 16 animals and over 30 weeks (chronic) in 8 animals using two USV elicitation paradigms (n = 16 non-elicited, spontaneous; n = 8 elicited, sexually paired). USV acoustic characteristics from a list of possible parameters (duration, principal frequency, complexity, power, and tonality) were compared across USV elicitation paradigms and time points (before RLN injury, 2 weeks after injury, and 30 weeks after injury).

Results: The USV parameters most impacted by RLN injury were frequency, power, and tonality, with significant decreases in all three parameters in both non-elicited/spontaneous and sexually elicited USV elicitation paradigms. All USV parameters were stable across 30 weeks after RLN injury.

Conclusion: USV acoustic frequency, power, and tonality best characterize RLN injury and are stable over time, demonstrating their ecological utility in characterizing RLN injury and recovery. Furthermore, their stability can ensure accurate outcome metrics for future studies. Finally, these parameters have direct translation to humans with vocal fold paralysis.

Level of evidence: N/A.