Analysis Method for the Neurological and Physiological Processes Underlying the Pitch-Shift Reflex

The Pitch-shift reflex (PSR) is the adjustment of the voice pitch during phonation or speech in response to a spontaneous perturbation (pitch-shift) of the perceived auditory feedback. The PSR is the result of the interaction of neurological and physiological processes underlying mechanisms for the pitch control during voice production. We present an experimental set-up for a comprehensive analysis of the PSR. Therefore, EEG, EGG, the voice signal and vocal fold dynamics are synchronously recorded and analysed for two paradigms, i.e. phonation (vowel /a/) and speech (['mama]). To visualise vocal fold dynamics, transnasal high-speed endoscopy (HSE) imaging was conducted. The PSR was elicited by a synthetic increase of the fundamental frequency of the auditory feedback. The occurrence of the PSR was verified by detecting the N100 and the Mismatch Negativity (MMN) in the EEG. For voice and EGG, statistical tests were applied to detect significant variations of the fundamental frequency due to the PSR. Additionally, the HSE footage was evaluated to judge for the applicability of PSR detection in comparison to the common voice and EGG signal. A preliminary study with five subjects was conducted. PSR was found in physiological latency ranges for EEG, EGG, and voice signals. Furthermore, the PSR was also successfully verified in the HSE data which showed similar sensitivity for PSR detection as EGG and voice signals. Hence, we suggest HSE as promising additional tool to gain further information on PSR processes due to the possibility of directly observing the vocal fold dynamics in detail.