Timing interference to speech in altered listening conditions

Abstract

A theory is outlined that explains the disruption that occurs when auditory feedback is altered. The key part of the theory is that the number of, and relationship between, inputs to a timekeeper, operative during speech control, affects speech performance. The effects of alteration to auditory feedback depend on the extra input provided to the timekeeper. Different disruption is predicted for auditory feedback that is out of synchrony with other speech activity (e.g., delayed auditory feedback, DAF) compared with synchronous forms of altered feedback (e.g., frequency shifted feedback, FSF). Stimulus manipulations that can be made synchronously with speech are predicted to cause equivalent disruption to the synchronous form of altered feedback. Three experiments are reported. In all of them, subjects repeated a syllable at a fixed rate (Wing & Kristofferson, 1973). Overall timing variance was decomposed into the variance of a timekeeper (Cv) and the variance of a motor process (Mv). Experiment 1 validated Wing and Kristofferson's method for estimating Cv in a speech task by showing that only this variance component increased when subjects repeated syllables at different rates. Experiment 2 showed DAF increased Cv compared with when no altered sound occurred (Experiment 1) and compared with FSF. In Experiment 3, sections of the subject's output sequence were increased in amplitude. Subjects just heard this sound in one condition and made a duration decision about it in a second condition. When no response was made, results were like those with FSF. When a response was made, Cv increased at longer repetition periods. The findings that the principal effect of DAF, a duration decision and repetition period is on Cv whereas synchronous alterations that do not require a decision (amplitude increased sections where no response was made and FSF) do not affect Cv, support the hypothesis that the timekeeping process is affected by synchronized and asynchronized inputs in different ways.

The neural substrates for atypical planning and execution of word production in stuttering

“…Finally, there is also evidence indicating an atypical interface between planning and execution processes (e.g., Blomgren and Goberman, 2008;Dworzynski et al, 2004;Savage and Howell, 2008;Snyder et al, 2009). That is, failure in speech fluency may result from dyssynchrony between cognitive-linguistic formulation of a speech plan and the motor execution of the linguistic plan (Howell, 2002(Howell, , 2004Howell and Sackin, 2002). However, it is still unclear what the neural substrates for atypical planning or execution are and how the neural substrates for the two atypical processes interact with each other.…”

Effects of altered auditory feedback (AAF) on stuttering frequency during monologue speech production

“…There is substantial clinical and experimental data showing immediate fluency enhancing effects of AAF for people who stutter (Armson, Kiefte, Mason, & De Croos, 2006;Howell, 2004;Lincoln, Packman, & Onslow, 2006). Although there is a large literature on the role of auditory feedback in speech production (Fairbanks, 1955;Howell & Sackin, 2002;Lee, 1950;Max, Guenther, Gracco, Ghosh, & Wallace, 2004;Postma, 2000;Postma & Kolk, 1992;Venkatagiri, 2005), the mechanism of stuttering reduction with AAF in people who stutter is not completely understood. Alterations to auditory feedback are usually made using an external stimulus that is produced by another speaker, talking in unison, or using an electronic feedback device.…”

Speech disruption during delayed auditory feedback with simultaneous visual feedback

“…However, we believe that it is unlikely that DAF effects arise from a close monitoring of the precision of production. Rather, we believe that DAF effects arise from monitoring a signal that is globally asynchronous (Howell and Sackin, 2002). The visual feedback we provided to speakers was inherently synchronous with their ongoing production and speakers may have been able to monitor this alternative feedback to some degree, thereby reducing the speech disruption caused by exposure to DAF.…”

“…Indeed, DAF effects are not limited to speech behaviors and are found with other motor behaviors such as tapping and music production (Chase et al, 1959;Smith et al, 1960;Finney and Warren, 2002). Thus, the root cause of DAF effects appears to be due to a more general disruption of the temporal relationship between production and acoustic input and not due to the fact that the feedback system receives incorrect information about the specific articulations (Howell and Sackin, 2002).…”