The Role of Auditory Feedback for Speech Intensity Regulation in Parkinson’s Disease
Abstract
Hypophonia (low speech intensity) has been found to be the most common speech symptom experienced by individuals with Parkinson’s disease (PD). Previous research suggests that, in the PD population, there may be abnormal integration of sensory information for motor production of speech intensity. In the current study, auditory feedback was systematically manipulated during sensorimotor conditions that are known to modulate speech intensity in everyday contexts. Twenty-six individuals with PD and twenty-four neurologically healthy controls were asked to complete the following tasks: converse with the experimenter with varying distances between the participant and listener (near and far distances), vowel prolongation, read sentences at a comfortable loudness, complete a magnitude production task (reading 2 times louder, 4 times louder, maximum loudness), and complete an imitation task (50dB, 60dB, 70dB, 80dB), while hearing their own speech intensity randomly altered. Altered intensity feedback conditions included 5, 10 and 15dB reductions and increases in the feedback intensity. Participants were also asked to read sentences with and without an instruction to attempt to ignore the auditory feedback. Speech tasks were completed in no noise, background noise, and a complete masking noise condition. Outcome measures included speech intensity (dB) and loudness perception ratings obtained using a visual analogue scale. Overall results indicate that individuals with PD display a reduced response to the altered intensity feedback in all speech tasks, suggestive of abnormal of processing of auditory feedback for speech intensity regulation. Specific deficits related to the perception of self-loudness are suggested based on the current findings. Clinical implications are discussed as they relate to understanding specific deficits of auditory processing for speech impairments in PD.