ULTRASONIC VOCALISATIONS AS A SURROGATE MARKER OF SPEECH DISTURBANCES IN PARKINSON’S DISEASE IN A RAT MODEL

Dysarthria affects up to 90% of Parkinson’s disease (PD) patients. Deep brain stimulation (DBS), an effective surgical intervention for advanced PD, also displays varied effects on speech, with some patients reporting improvement in speech and others worsened dysarthria and dysphonia. The aim of this study was to develop a speech biomarker in the hemiparkinsonian 6-OHDA rat model and to investigate the effects of subthalamic nucleus (STN) DBS on speech.
Male and female Wistar rats allocated to PD (N=9) and sham operated group (N=11) were studied. Ultrasonic vocalisations (USVs) were recorded during ‘tickling’ the upper chest and recorded using a USB ultrasonic microphone (Petterson M500). Using spectrogram analysis, USV were manually classified into trill, flat, and frequency-modulated calls based on frequency range and morphology (Matlab2024b). Duration, frequency range, and median frequency of each call were automatically extracted for analysis.
We found a decrease in the number of calls in PD compared to sham controls over all call types with little changes in call distribution and parameters. The application of DBS in the PD group on the other hand resulted in changes in call morphology: frequency range of thrills increased with the application of DBS. Duration of flat call increased significantly in PD rats but was normalised with the application of DBS.
USVs were reduced in the rat PD model and STN-DBS had varied effects on speech architecture in our rodent model of PD. Including a surrogate marker for speech will support a comprehensive preclinical evaluation of neuromodulation therapies in PD.