Timing variability of sensorimotor integration during vocalization in individuals who stutter

Abstract

Persistent developmental stuttering affects close to 1% of adults and is thought to be a problem of sensorimotor integration. Previous research has demonstrated that individuals who stutter respond differently to changes in their auditory feedback while speaking. Here we explore a number of changes that accompany alterations in the feedback of pitch during vocal production. Participants sustained the vowel /a/ while hearing on-line feedback of their own voice through headphones. In some trials, feedback was briefly shifted up or down by 100 cents to simulate a vocal production error. As previously shown, participants compensated for the auditory pitch change by altering their vocal production in the opposite direction of the shift. The average compensatory response was smaller for adults who stuttered than for adult controls. Detailed analyses revealed that adults who stuttered had fewer trials with a robust corrective response, and that within the trials showing compensation, the timing of their responses was more variable. These results support the idea that dysfunctional sensorimotor integration in stuttering is characterized by timing variability, reflecting reduced coupling of the auditory and speech motor systems.

Neural Correlates of Vocal Pitch Compensation in Individuals Who Stutter

“…Consistent with this idea is the observation that individuals who stutter do not respond to altered auditory feedback in the same way as fluent individuals during vocalization (Kalinowski et al, 1993;Bauer et al, 2007;Cai et al, 2012;Loucks et al, 2012;Daliri et al, 2018). We recently showed that individuals who stutter are more variable in responding to manipulations of pitch feedback while speaking, both in the number of compensatory responses and in the timing of those responses, and that this variability correlates with self-rated stuttering severity (Sares et al, 2018). The results of this and other behavioral studies (Kalinowski et al, 1993;Cai et al, 2014) point to a timing problem during auditory-motor behavior, something that also appears to extend to non-speech (Cooper and Allen, 1977;Ward, 1997;Boutsen et al, 2000;Subramanian and Yairi, 2006;Falk et al, 2015;van de Vorst and Gracco, 2017;Sares et al, 2019).…”

Adults who stutter and metronome synchronization: evidence for a nonspeech timing deficit

“…After exclusions, 14 AC (5 males and 9 females) and 13 AS (6 males and 7 females) were left. This is the same group of individuals reported for our recent study on vocal pitch compensation, except that here one more individual is excluded because of syncopation behavior. The participants ranged in age from 18 to 51 years (mean 28 ± 10 for the stuttering group, mean 26 ± 8 for the controls; no group difference: t (26) = –0.609, P = 0.548).…”

“…Stuttering is a speech disorder involving repetitions or prolongations of phonemes, syllables, or words, as well as blocks in speech. One of the characteristics of the fluent speech of individuals who stutter is a difference in speech timing evidenced by increased variability, a lack of interarticulator coordination, and atypical responses to perturbed auditory feedback . Thus, it has been suggested that stuttering behavior may be related to a timing deficit that is sensorimotor in nature .…”

Decreased sensitivity to changing durational parameters of syllable sequences in people who stutter

“…There are some, albeit partly conflicting indications for more variable motor timing in children who stutter when they are asked to uphold a steady clapping rate after external pacing is removed (Olander, Smith, & Zelaznik, 2010; but see Hilger, Zelaznik, & Smith, 2016). Recently, it has been shown that PWS demonstrate subtle timing differences in a task requiring manual motor synchronisation with variable metronome sequences (Sares, Deroche, Shiller, & Gracco, 2019). There is also evidence for co-variation of such basic motor timing abilities and speech timing abilities and stuttering severity (Cooper & Allen, 1977;Falk et al, 2015).…”

“…The effectiveness of auditory feedback manipulations, particularly of delayed auditory feedback, in elevating stuttering symptoms is long established (Lotzmann, 1961;Soderberg, 1968). However, PWS also show more variable timing in their response to feedback (pitch) manipulations of their own voice delivered by headphones (Sares, Deroche, Shiller, & Gracco, 2018). Differences in speech and non-speech timing, correlations between nonspeech timing abilities and stuttering severity, effects of temporal feedback manipulations on speech motor fluency, and variable timing in response to pitch feedback manipulations seem to point toward global temporal processing differences that affect production and perception of temporal structure in PWS.…”