Delayed Auditory Feedback Elicits Specific Patterns of Serial Order Errors in a Paced Syllable Sequence Production Task.

PURPOSE: Delayed auditory feedback (DAF) interferes with speech output. DAF causes distorted and disfluent productions and errors in the serial order of produced sounds. Although DAF has been studied extensively, the specific patterns of elicited speech errors are somewhat obscured by relatively small speech samples, differences across studies, and uncontrolled variables. The goal of this study was to characterize the types of serial order errors that increase under DAF in a systematic syllable sequence production task, which used a closed set of sounds and controlled for speech rate. METHOD: Sixteen adult speakers repeatedly produced CVCVCV (C = consonant, V = vowel) sequences, paced to a "visual metronome," while hearing self-generated feedback with delays of 0-250 ms. Listeners transcribed recordings, and speech errors were classified based on the literature surrounding naturally occurring slips of the tongue. A series of mixed-effects models were used to assess the effects of delay for different error types, for error arrival time, and for speaking rate. RESULTS: DAF had a significant effect on the overall error rate for delays of 100 ms or greater. Statistical models revealed significant effects (relative to zero delay) for vowel and syllable repetitions, vowel exchanges, vowel omissions, onset disfluencies, and distortions. Serial order errors were especially dominated by vowel and syllable repetitions. Errors occurred earlier on average within a trial for longer feedback delays. Although longer delays caused slower speech, this effect was mediated by the run number (time in the experiment) and small compared with those in previous studies. CONCLUSIONS: DAF drives a specific pattern of serial order errors. The dominant pattern of vowel and syllable repetition errors suggests possible mechanisms whereby DAF drives changes to the activity in speech planning representations, yielding errors. These mechanisms are outlined with reference to the GODIVA (Gradient Order Directions Into Velocities of Articulators) model of speech planning and production. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.19601785.

Visuomotor control of neck surface electromyography in Parkinson's disease.

OBJECTIVE: To compare performance of individuals with Parkinson's disease (PD) and age-matched controls on a visuomotor tracking task controlled via surface electromyography (sEMG). METHODS: Twenty-seven adults with PD and twenty-four older controls produced dry swallows and completed a visuomotor tracking task utilizing both static and dynamic targets. sEMG was recorded at the anterior neck and submental surface during both tasks. RESULTS: There was no significant difference in visuomotor tracking ability between cohorts. Post hoc analyses indicated that there was no significant difference between participant groups in the strength or duration of swallows as measured by sEMG but that participants with PD showed a trend for decreased swallow durations at the anterior neck (padj = 0.067) whereas controls showed a trend for increased durations at the anterior neck (padj = 0.112), compared to the submental surface. However, there were no significant correlations between swallowing behavior and visuomotor tracking ability. CONCLUSION: There were no significant differences in visuomotor tracking performance between individuals with PD and controls. Furthermore, there was no relationship between tracking ability and swallowing behavior. We conclude that sEMG-mediated biofeedback may have limited promise as a tool for treating PD-related dysphagia.