Research

Examining neural oscillations -- rhythmic fluctuations of neural excitability -- provides an opportunity to better understand the neurophysiological bases of the auditory-motor coordination deficits that have been reported in stuttering speakers. Fluent speech requires coordinated neuronal activity that is achieved through neural oscillatory synchrony across brain structures. The overall objective of this study is to determine how children who stutter (CWS) differ from fluent peers in neural oscillatory synchrony across auditory-motor structures during speech perception, planning, and production under two conditions - with and without rhythmic entrainment. Guided by EEG and MRI data collected from children who do and do not stutter, our central hypothesis is that beta oscillations, which control predictive timing of movements through coordination of motor to auditory systems, will show aberrant power, reduced inter-trial phase clustering, and reduced interregional oscillatory phase synchrony in CWS. A better understanding in this area has exciting treatment implications, since manipulation of synchrony within oscillatory patterns in auditory-motor systems may be possible through entrainment with external sensory stimuli and non-invasive brain stimulation. This project will thus allow us to lay the groundwork towards systematic, neurobiology-based intervention development for CWS. This research will be the first series of studies designed to characterize neural oscillatory synchrony specific to speech processing in CWS, which may serve as a highly predictive neural marker for persistent stuttering during early childhood. The findings are expected to elucidate, for the first time, causal mechanisms behind auditory-motor integration deficits in persistent stuttering. Such results will have an important positive impact, as the identified neural mechanisms underlying fluent speech will lay the foundation for effective early intervention for stuttering.

This research is funded through an NIDCD/NIH R01 grant R01DC018283 (PI: Chang)

Many models of speech timing have proposed that speech, like other motor activities, is rhythmically structured in time. Rhythm can be defined as a pattern of durations marked by a series of events, and perceptually as the temporal organization of the physical sound pattern.  One of the hallmarks of skilled motor behavior such as fluent speech production is accurate timing, and the possible critical role of aberrant temporal processing in stuttering has been one of the oldest and most dominant perspectives in the field. However, studies examining temporal processing in children who stutter have been rare.  In our studies, we have used a rhythm perception task (auditory perceptual timing) to show that children who stutter exhibit significantly reduced rhythm discrimination performance compared to controls. The task relies on the ability to perceive the temporal organization of a sequence of tones, which taxes intrinsic timing ability (i.e., internal generation of a beat) without the confounding effects of speech production. CWS showed poorer rhythm discrimination relative to controls, especially in the complex condition where the “beats” occurring in rhythms are not explicitly marked and hence require greater internal generation of timing. In addition, CWS showed aberrant brain connectivity involving the cortico-BG networks, and a negative correlation between rhythm discrimination performance and functional connectivity of basal ganglia (BG) and cerebellum (CE). In terms of rhythm production (motor timing), the extant data are conflicting, for example based on tapping task performance in adults who stutter. Examining the relationship between  performance on temporal processing tasks and brain connectivity in the “timing networks” that involve both BG and CE circuits is expected  to provide breakthroughs in our understanding of the neurobiological bases of timing control deficits that may underlie persistent developmental stuttering. 

Combining neuroimaging and behavioral experiments that involve rhythm perception and production tasks, we are conducting parallel series of studies to investigate a novel rhythm deficit hypothesis in stuttering. This study is in collaboration with Drs. Devin McAuley at Michigan State University.

This study is funded by the NIDCD/NIH grant R01 DC011277 (PI Chang), Grammy Foundation and the RAIND (Research in Autism, Intellectual, and Neurodevelopmental Disabilities) pilot grant (PIs McAuley, Chang, Wade, Dilley).