Rodent ultrasonic mating calls as a biomarker for oromotor deficits in Parkinsonian animal model
Neurodegenerative diseases, such as Parkinson’s disease (PD), likely initiate their pathologies primarily within the brain and later manifest themselves in daily behavioral functions. In patients with PD, the loss of dopaminergic neurons in the basal ganglia results in sensorimotor deficits, including tremor, bradykinesia, olfactory function loss, speech/voice loss, and eating disorders. Although not much is known about the etiology of Parkinson’s disease, extensive studies have focused on correlating different signs of motor degradation with the degree of dopaminergic neuron loss. Despite the fact that different animal models and diverse behavioral methods have been developed to further characterize limb motor function loss, the loss of fine oromotor function, which includes eating/biting disorders and voice/speech loss, has been largely overlooked due to its intrinsic complexity as well as the lack of a precise method for quantitative description. An animal model was developed for the study of oromotor deficits in PD that utilizes the production of ultrasonic vocalization in lab rodents. Parkinsonian animals suffer the same symptoms in their vocalization compared to human PD patients: a significant drop of intensity and pitch variation. Furthermore, a newly developed biting test provided evidence that the animal’s oromotor function have been compromised due to dopamine loss. Overall, these studies show that qualitative analysis of the ultrasonic vocalizations (USVs) of laboratory rats can serve as a sensitive behavioral biomarker for the detection of subtle oromotor deficits in neurodegenerative diseases.