Acuity to Changes in Self-Generated Vocal Pitch in Parkinson's Disease

Abstract

Purpose Given the role of auditory perception in voice production, studies have investigated whether impairments in auditory perception may underlie the noted disruptions in speech in Parkinson's disease (PD). Studies of loudness perception in PD show impairments in the perception of self-generated speech, but not external tones. Studies of pitch perception in PD have only examined external tones, but these studies differed in terms of the interstimulus intervals (ISIs) that were used, did not examine the impact of cognition, and report conflicting results. To clarify pitch perception in PD, this work investigated perception of self-generated vocal pitch, controlling for cognition and ISI. Method A total of 30 individuals with and without PD completed (a) hearing threshold testing, (b) the Montreal Cognitive Assessment, and (c) an adaptive just-noticeable-difference paradigm under two separate ISIs (100 ms and 1,000 ms) to assess acuity to self-generated vocal pitch. Results There was no significant difference in acuity between individuals with and without PD. Both groups demonstrated significantly worse acuity for longer compared to shorter ISIs. Montreal Cognitive Assessment scores were not a significant predictor of acuity. Conclusions The results suggest that acuity to self-generated vocal pitch does not differ between individuals with and without PD.

Figure 1.

The just-noticeable-difference (JND) paradigm is shown for a participant with Parkinson's disease (PD28) during the 1,000-ms interstimulus interval condition with “reversals” (changes in direction of the adaptive paradigm) numbered from 1 to 10. The difference in voice fundamental frequency (f _o) in semitones between the two stimuli played is plotted as a function of trial number. The JND (discrimination threshold; red dashed line) was determined for each participant as the average of the last six reversals.

Figure 2.

The just-noticeable-difference (JND) values are shown by interstimulus interval condition of 100 ms (circles) or 1,000 ms (squares) for individuals with Parkinson's disease (PD group; dark blue) and individuals without Parkinson's disease (control group; light blue). The error bars indicate 95% confidence intervals. The asterisks display significant differences and “ns” displays a nonsignificant difference.

Figure 3.

The average just-noticeable-difference (JND) values across the 100-ms and 1,000-ms conditions are shown by Montreal Cognitive Assessment (MoCA) score for individuals with Parkinson's disease (PD group, dark blue) and individuals without Parkinson's disease (control group, light blue).