ABSTRACT
Auditory feedback perturbation studies have indicated a link between feedback and feedforward mechanisms in speech production when participants compensate for applied shifts. In spectral perturbation studies, speakers with a higher perceptual auditory acuity typically compensate more than individuals with lower acuity. However, the reaction to feedback perturbation is unlikely to be merely a matter of perceptual acuity but also affected by the prediction and production of precise motor action. This interplay between prediction, perception, and motor execution seems to be crucial for the timing of speech and non-speech motor actions. In this study, to examine the relationship between the responses to temporally perturbed auditory feedback and rhythmic abilities, we tested 45 adult speakers on the one hand with a temporal auditory feedback perturbation paradigm, and on the other hand with rhythm perception and production tasks. The perturbation tasks temporally stretched and compressed segments (onset + vowel or vowel + coda) in fluent speech in real-time. This technique sheds light on the temporal representation and the production flexibility of timing mechanisms in fluent speech with respect to the structure of the syllable. The perception tasks contained staircase paradigms capturing duration discrimination abilities and beat-alignment judgments. The rhythm production tasks consisted of finger tapping tasks taken from the BAASTA tapping battery and additional speech tapping tasks. We found that both auditory acuity and motor stability in finger tapping affected responses to temporal auditory feedback perturbation. In general, speakers with higher auditory acuity and higher motor variability compensated more. However, we observed a different weighting of auditory acuity and motor stability dependent on the prosodic structure of the perturbed sequence and the nature of the response as purely online or adaptive. These findings shed light on the interplay of phonological structure with feedback and feedforward integration for timing mechanisms in speech.
ABSTRACT
Auditory feedback perturbations involving spectral shifts indicated a crucial contribution of auditory feedback to planning and execution of speech. However, much less is known about the contribution of auditory feedback with respect to temporal properties of speech. The current study aimed at providing insight into the representation of temporal properties of speech and the relevance of auditory feedback for speech timing. Real-time auditory feedback perturbations were applied in the temporal domain, viz., stretching and compressing of consonant-consonant-vowel (CCV) durations in onset + nucleus vs vowel-consonant-consonant (VCC) durations in nucleus + coda. Since CCV forms a gesturally more cohesive and stable structure than VCC, greater articulatory adjustments to nucleus + coda (VCC) perturbation were expected. The results show that speakers compensate for focal temporal feedback alterations. Responses to VCC perturbation were greater than to CCV perturbation, suggesting less deformability of onsets when confronted with temporally perturbed auditory feedback. Further, responses to CCV perturbation rather reflected within-trial reactive compensation, whereas VCC compensation was more pronounced and indicative of adaptive behavior. Accordingly, planning and execution of temporal properties of speech are indeed guided by auditory feedback, but the precise nature of the reaction to perturbations is linked to the structural position in the syllable and the associated feedforward timing strategies.
