The overall goal of this project is to better understand the fundamental physiological and neural mechanisms that contribute to disfluencies in children who stutter (CWS). Our research strategy combines both ground-breaking and established experimental approaches including functional near-infrared spectroscopy (fNIRS - an emerging neuroimaging technology), kinematic measures of articulation, and clinical assessments of stuttering severity. An overall goal of this project is to examine activation of specific neural regions involved in speech production during a range of speaking conditions, including natural speech, using fNIRS. Findings from nearly 20 years of functional neuroimaging research in adults who stutter have provided greater insight into the neurological underpinnings of developmental stuttering. Because there have been few studies in CWS, however, it is unclear whether differences detected in adults who stutter are present at onset or emerge later, a consequence of a lifetime of compensation and/or therapeutic strategies. An additional limitation of earlier neuroimaging studies is the use of brief, unnatural speaking tasks due to methodological constraints inherent in fMRI and PET technologies. Stuttering occurs during natural, extemporaneous, connected speech. Therefore, it is critical to assess neural activation during more ecologically valid speaking conditions that place the greatest demands on the speech motor system of the CWS. Functional NIRS can be used to achieve this aim, because it is uniquely suited to record brain hemodynamics during natural speaking conditions. Another aim of this research is to examine relationships among central correlates of speech production, peripheral motor speech dynamics, and behavioral indices of stuttering. We will address this aim with parallel kinematic and neuroimaging experiments for a range of speaking conditions in which linguistic complexity and auditory feedback are manipulated. A relatively large group of CWS will be recruited to ensure that a range of clinical severity is represented. By incorporating a theoretically-grounded hierarchy of experiments designed to elicit a continuum of fluency, we will determine if potential changes in stuttering behavior are associated with differences in neural activation and speech motor coordination in CWS. Findings from this project will provide a critical step for future work using these noninvasive methods to identify neural characteristics of young children at risk for persistence in stuttering.
Chronic stuttering, which affects nearly 1% of the population world-wide, often has life-long negative consequences, including poorer mental health and emotional well-being, and reduced educational and employment achievements. This project is highly relevant the mission of NIDCD with its focus on understanding fundamental neurophysiological underpinnings of developmental stuttering and how these mechanisms relate to clinical measures of stuttering severity. The long term implications of this work for bot the diagnosis and treatment of stuttering are substantial. Functional NIRS shows promise as a research tool to study the developmental course of atypical lateralization of speech and language processes in young children who are stuttering. This emerging neuroimaging technology also offers promise as a means to assess potential neural reorganization that occurs with behavioral treatment paradigms for chronic stuttering.