Matthias K. Franken

Modulations of the auditory M100 in an imitation task.

Models of speech production explain event-related suppression of the auditory cortical response as reflecting a comparison between auditory predictions and feedback. The present MEG study was designed to test two predictions from this framework: (1) whether the reduced auditory response varies as a function of the mismatch between prediction and feedback; (2) whether individual variation in this response is predictive of speech-motor adaptation. Participants alternated between online imitation and listening tasks. In the imitation task, participants began each trial producing the same vowel (/e/) and subsequently listened to and imitated auditorily-presented vowels varying in acoustic distance from /e/. Results replicated suppression, with a smaller M100 during speaking than listening. Although we did not find unequivocal support for the first prediction, participants with less M100 suppression were better at the imitation task. These results are consistent with the enhancement of M100 serving as an error signal to drive subsequent speech-motor adaptation.

Individual variability as a window on production-perception interactions in speech motor control

An important part of understanding speech motor control consists of capturing the interaction between speech production and speech perception. This study tests a prediction of theoretical frameworks that have tried to account for these interactions: If speech production targets are specified in auditory terms, individuals with better auditory acuity should have more precise speech targets, evidenced by decreased within-phoneme variability and increased between-phoneme distance. A study was carried out consisting of perception and production tasks in counterbalanced order. Auditory acuity was assessed using an adaptive speech discrimination task, while production variability was determined using a pseudo-word reading task. Analyses of the production data were carried out to quantify average within-phoneme variability, as well as average between-phoneme contrasts. Results show that individuals not only vary in their production and perceptual abilities, but that better discriminators have more distinctive vowel production targets-that is, targets with less within-phoneme variability and greater between-phoneme distances-confirming the initial hypothesis. This association between speech production and perception did not depend on local phoneme density in vowel space. This study suggests that better auditory acuity leads to more precise speech production targets, which may be a consequence of auditory feedback affecting speech production over time.

Listening for speaking: Investigations of the relationship between speech perception and production

An important part of understanding speech motor control consists of capturing the interaction between speech production and speech perception. This study tests a prediction of theoretical frameworks that have tried to account for these interactions: if speech production targets are specified in auditory terms, individuals with better auditory acuity should have more precise speech targets, evidenced by decreased within-phoneme variability and increased between-phoneme distance. A study was carried out consisting of perception and production tasks in counterbalanced order. Auditory acuity was assessed using an adaptive speech discrimination task, while production variability was determined using a pseudo-word reading task. Analyses of the production data were carried out to quantify average within-phoneme variability as well as average between-phoneme contrasts. Results show that individuals not only vary in their production and perceptual abilities, but that better discriminators have more distinctive vowel production targets – that is, targets with less within-phoneme variability and greater between-phoneme distances – confirming the initial hypothesis. This association between speech production and perception did not depend on local phoneme density in vowel space. This study suggests that better auditory acuity leads to more precise speech production targets, which may be a consequence of auditory feedback affecting speech production over time. This chapter was based on: Franken, M. K., Acheson, D.J., McQueen, J. M., Eisner, F., & Hagoort, P. (2017). Individual variability as a window on production-perception interactions in speech motor control. Journal of the Acoustical Society of America, 142(4): 2007-2018.

Self-monitoring in the cerebral cortex: Neural responses to small pitch shifts in auditory feedback during speech production

&NA; Speaking is a complex motor skill which requires near instantaneous integration of sensory and motor‐related information. Current theory hypothesizes a complex interplay between motor and auditory processes during speech production, involving the online comparison of the speech output with an internally generated forward model. To examine the neural correlates of this intricate interplay between sensory and motor processes, the current study uses altered auditory feedback (AAF) in combination with magnetoencephalography (MEG). Participants vocalized the vowel/e/and heard auditory feedback that was temporarily pitch‐shifted by only 25 cents, while neural activity was recorded with MEG. As a control condition, participants also heard the recordings of the same auditory feedback that they heard in the first half of the experiment, now without vocalizing. The participants were not aware of any perturbation of the auditory feedback. We found auditory cortical areas responded more strongly to the pitch shifts during vocalization. In addition, auditory feedback perturbation resulted in spectral power increases in the &thgr; and lower &bgr; bands, predominantly in sensorimotor areas. These results are in line with current models of speech production, suggesting auditory cortical areas are involved in an active comparison between a forward models prediction and the actual sensory input. Subsequently, these areas interact with motor areas to generate a motor response. Furthermore, the results suggest that &thgr; and &bgr; power increases support auditory‐motor interaction, motor error detection and/or sensory prediction processing. HighlightsParticipants listened to unexpected auditory feedback during speech production.Auditory cortex response reflects comparison between an internal forward model and auditory feedback.Increased theta power over motor areas reflect increased sensorimotor processing.Increased lower beta power over motor areas may reflect motor error processing or auditory prediction.