Abstract
Altering reafferent sensory information can have a profound effect on motor output. Introducing a short delay [delayed auditory feedback (DAF)] during speech production results in modulations of voice and loudness, and produces a range of speech dysfluencies. The ability of speakers to resist the effects of delayed feedback is variable yet it is unclear what neural processes underlie differences in susceptibility to DAF. Here, susceptibility to DAF is investigated by looking at the neural basis of within and between subject changes in speech fluency under 50 and 200 ms delay conditions. Using functional magnetic resonance imaging, networks involved in producing speech under two levels of DAF were identified, lying largely within networks active during normal speech production. Independent of condition, fluency ratings were associated with midbrain activity corresponding to periaqueductal grey matter. Across subject variability in ability to produce normal sounding speech under a 200 ms delay was associated with activity in ventral sensorimotor cortices, whereas ability to produce normal sounding speech under a 50 ms delay was associated with left inferior frontal gyrus activity. These data indicate whilst overlapping cortical mechanisms are engaged for speaking under different delay conditions, susceptibility to different temporal delays in speech feedback may involve different processes.
Highlights
A one way repeated measures analysis of variance (ANOVA) revealed significant differences between the scores assigned to sentences spoken under the three different conditions of DAF200, DAF50, and no delay [F(2,42) 1⁄4 42.852, p < 0.001] means/standard deviations 3.59 þ/À 1.94, 5.14 þ/À 2.0, 8.20 þ/À 1.18, respectively)
Previous work has repeatedly shown that a 200 ms delay in auditory feedback during speech production results in maximal dysfluency, but that individual variability in response is high
Independent of variability in susceptibility to delayed auditory feedback (DAF), we confirm previous findings that altered auditory feedback during speech production is associated with activity in posterior superior temporal cortices (Hashimoto and Sakai, 2003; Takaso et al, 2010), and that speech production under 200 and 50 ms delays lie largely within in a region activated with speech production in general
Summary
Susceptibility to alterations in feedback reveals aspects of the role of sensory processing during motor control of speech. Rapid compensatory responses to altered F0 provide a biological marker for feedback sensitivity in vocal control of pitch (Jones and Munhall, 2000; Kort et al, 2014). Delayed auditory feedback (DAF) (the induction of a temporal asynchrony between speech motor commands and auditory feedback) reveals a sensitivity to temporal aspects of auditory feedback. Overreliance on reafference information is thought to play a role in stuttering, which shares many behavioral similarities to DAF affected speech (Grafton et al, 1997). Introducing a delay in feedback, which perhaps modifies any overreliance on reafferent information, is known to improve speech fluency in people who stutter (Foundas et al, 2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
