Abstract
Stuttering is a disorder that impacts the smooth flow of speech production and is associated with a deficit in sensorimotor integration. In a previous experiment, individuals who stutter were able to vocally compensate for pitch shifts in their auditory feedback, but they exhibited more variability in the timing of their corrective responses. In the current study, we focused on the neural correlates of the task using functional MRI. Participants produced a vowel sound in the scanner while hearing their own voice in real time through headphones. On some trials, the audio was shifted up or down in pitch, eliciting a corrective vocal response. Contrasting pitch-shifted vs. unshifted trials revealed bilateral superior temporal activation over all the participants. However, the groups differed in the activation of middle temporal gyrus and superior frontal gyrus [Brodmann area 10 (BA 10)], with individuals who stutter displaying deactivation while controls displayed activation. In addition to the standard univariate general linear modeling approach, we employed a data-driven technique (independent component analysis, or ICA) to separate task activity into functional networks. Among the networks most correlated with the experimental time course, there was a combined auditory-motor network in controls, but the two networks remained separable for individuals who stuttered. The decoupling of these networks may account for temporal variability in pitch compensation reported in our previous work, and supports the idea that neural network coherence is disturbed in the stuttering brain.
Highlights
Persistent developmental stuttering is a neurobiological disorder that results in the repetition and prolongation of speech sounds, syllables, and words (Bloodstein and Bernstein Ratner, 2008)
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)
Though an attenuated average response in adults who stutter (AWS) compared to adult controls (AC) is visually evident, the group difference in area under the curve did not reach significance, whereas it had in the outof-scanner data (F(1,26) = 1.5, p = 0.235, ηG2 = 0.04)
Summary
Persistent developmental stuttering is a neurobiological disorder that results in the repetition and prolongation of speech sounds, syllables, and words (Bloodstein and Bernstein Ratner, 2008). 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 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). We will explore the neural processes underlying altered pitch feedback compensation in individuals who stutter using fMRI
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