Auditory Feedback Control of Vocal Pitch in Spasmodic Dysphonia

Authors | Arthur Thomas BA, Natasha Mirza MD, Steven J. Eliades MD, PhD
University of Pennsylvania Perelman School of Medicine

Presented at Combined Otolaryngology Spring Meetings 2020 Virtual Poster Presentation, Poster E164 and published in 3 Laryngoscope, 2020

Arthur Thomas BA, Natasha Mirza MD, Steven J. Eliades MD PhD

In individuals with normal voice, there are well-described reflexes involved in the control of voice that allow detection and correction of vocal production errors. One of these reflexes is the so-called vocal pitch reflex, where subjects who hear the sound of their own voice (which we call feedback) shifted up or down in pitch will compensate by changing their voice in the opposite direction. This reflex is rapid, typically occurring in a fraction of a second, and is automatic, not a result of a conscious decision. What is not clear is if this reflex is normal in patients with speech and voice disorders like spasmodic dysphonia (SD).

To investigate this, we tested 15 SD patients and 11 non-SD subjects. We had subjects repeat the vowel /e/ into a microphone while wearing headphones over their ears. At unpredictable times during their vowel production, we changed what they heard of their own voice through the headphones, increasing or decreasing the pitch by 2/12ths of an octave on a musical scale. Our SD patients not only compensated for the feedback pitch shift, changing their voice in the opposite direction, they did so with a magnitude twice that of our non-SD subjects. SD patients also showed greater variability in the timing of this reflex compared to non-SD individuals.

These results are consistent with an emerging idea that there is increased sensitivity to sensory feedback in SD, regardless of whether it is direct laryngeal sensation or sound, and that coordination between sensory and motor systems in the brain may be hyperactive. Dysfunction of this global ‘sensory-motor’ coordination may be a possible brain mechanism that leads to the symptoms of SD, though it is still unclear why such dysfunction might have come about in the first place. Our findings also have the potential to lead to new treatment approaches based on changing sensory feedback. Future work will need to examine whether or not feedback changes, like pitch shifts, affect the frequency or severity of vocal symptoms.