Background: Sensorimotor integration mechanisms can be affected by many factors, among which are those involving neuromuscular disorders. Parkinson's disease (PD) is characterized by well-known motor symptoms, among which lately have been included motor speech deficits. Measurement of the acoustic startle reflex (ASR) and its modulations (prepulse inhibition and prepulse facilitation, PPI and PPF respectively) represent a simple and quantifiable tool to assess sensorimotor function. However, it remains unknown whether measures of the PPI and PPF are associated with motor speech deficits in PD.
Methods: A total of 88 subjects participated in this study, 52 diagnosed with PD and 36 control subjects. After obtaining written informed consent, participants were assessed with PPI at several interstimulus intervals, and PPF at 1000 ms using the SRH-Lab system (San Diego, CA). Percentage of change in the amplitude and latency of the ASR was analyzed between groups. Voice recordings were register of a specific text given to the subjects with a professional recorder and temporal patterns of speech were analyzed.
Results: Statistical analysis conducted in this study showed differences in PPI and PPF in subjects with PD compared to controls. In addition, discriminative parameters of voice abnormalities were observed in PD subjects related to control subjects showing a reduction in phonation time, vowel pulses, breaks, breakage and voice speech periods.
Conclusions: PD presents a disruption in sensorimotor filter mechanisms and speech disorders, and there is a relationship between these alterations. The correlation between the PPI and PPF with an alteration of the voice in PD subjects contributes toward understanding mechanism underlying the neurophysiological alterations in both processes. Overall, easy and non-invasive tests such as PPI, PPF together with voice analysis may be useful to identify early stages of PD.