Characteristics of Voice Onset Time among Speakers of Jordanian Arabic with Parkinson’s Disease

Background: The voice onset time (VOT) is an acoustic measure to assess speech neuroregulatory mechanisms. However, the VOT was not measured in individuals of Jordanian Arabic with Parkinson's Disease (PD). Therefore, this research aimed to measure the VOT using a cross-sectional design. Sixteen individuals with PD and 16 healthy controls had their VOT assessed under two treatment conditions (Off and On-medication). The VOT was measured in several phonetic contexts. The results revealed a higher VOT effect among voiceless consonants for the PD in both experimental conditions than controls. Whereas no effects were observed among the voiced consonants between the two groups. In comparison, no differences were observed in the VOT between the voiceless and voiced consonants among the PD group in the Off-medication condition. The administration of the levodopa affected the VOT measure; a significant decrease in VOT among the voiceless and voiced consonants was observed between the Off and On-medication conditions. Additionally, no significant impacts on VOT were found among the PD individuals when comparing front and back consonants, rounded and unrounded vowels, high and low vowels, and among words versus a sentence. However, the VOT may vary according to the phonetic characteristics of speech and medication status among patients with PD. The VOT is still considered a sensitive acoustic measure to investigate speech production's neuroregulatory mechanisms and levodopa's effect among individuals with PD in Arabic. Notably, these acoustical markers only represent the first step in the objective biological screening of PD from speech signals.