An Integrated Approach to Concurrently Measure Corrective and Adaptive Responses to Auditory Errors

The brain relies on feedforward and feedback control systems to produce speech movements. Both control systems use auditory errors to generate responses that ensure the accuracy of speech movements. Traditionally, separate auditory perturbation paradigms are used to examine these control systems in isolation; however, this conventional practice is time-consuming and poses practical challenges. This study aimed to develop a new paradigm to examine both control systems concurrently.

We applied different auditory perturbation magnitudes (0, 125, 250, and 500 Hz) and directions (ε-to-ɪ and ε-to-ӕ) that randomly changed every six trials. We measured formant changes during early (0-100 ms) and late (200-300 ms) time points of production. Early response was used to calculate adaptive responses (a measure of the feedforward control system). The difference between late and early responses was used to calculate corrective responses (a measure of the feedback control system).

We found that participants produced (a) adaptive and corrective responses in the opposite direction of the perturbation direction and (b) proportionally larger adaptive and corrective responses to the smallest perturbation in the ε-to-ɪ direction. Additionally, participants who responded more to ε-to-ɪ perturbations also responded more to ε-to-ӕ perturbations.

These findings suggest that (a) the brain may have similar error sensitivity in the ε-to-ɪ and ε-to-ӕ directions and considers error magnitudes in preparing its responses to errors, and (b) our proposed paradigm is a promising approach to efficiently and concurrently measure the contributions of the feedback and feedforward controls systems.