Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Neural Correlates of Motor Speech Sequence Learning in Adults Who Stutter and Neurotypical Speakers
Poster Session D, Saturday, October 26, 10:30 am - 12:00 pm, Great Hall 3 and 4
Jackie S. Kim1, Haochen Wan2, Jason A. Tourville1, Barbara Holland1, Alfonso Nieto-Castañón1,3, Frank H. Guenther1,2,4; 1Boston University, 2Department of Biomedical Engineering, Boston University, Boston, MA, 3McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, 4Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA
Stuttering is a multifactorial neurodevelopmental motor speech disorder that affects a speaker’s ability to produce fluent speech. Previous literature suggests that stuttering interrupts the execution, rather than the learning, of new phonemic sequences at the single-syllable level. The Gradient Order Directions into Velocities of Articulators model posits that stuttering involves structural/functional anomalies in the motor loop, specifically in the left ventral premotor cortex and/or to impaired processing within the cortico-basal ganglia loop. Despite extensive neuroimaging studies on people who stutter, the underlying neural mechanisms involved in speech sequencing remain unclear. Therefore, the current fMRI study investigated speech motor sequence learning through a non-word repetition task in 15 adults who stutter (AWS) and 15 age-matched neurotypical controls (NT). Participants performed a nonword repetition task across two consecutive days, where they practiced three-syllable subsets of six-syllable nonwords with phonotactically legal consonant clusters in English. All stimuli and condition lists (novel vs. learned) were balanced across and within groups. Behavioral results analyzing error rates before and after training demonstrated that although AWS were less accurate than NT overall, both groups showed similar learning trajectories over time. Neuroimaging results based on the BOLD response during production of novel and learned words revealed no significant group differences – both groups demonstrated increased brain activation in regions linked to phonological working memory (bilateral pre-supplementary motor area and posterior inferior frontal gyrus), speech motor planning (left ventral premotor cortex), auditory processing (posterior superior temporal gyrus), and speech articulation (left anterior insula and frontal operculum). These findings are consistent with prior motor speech sequence learning studies in AWS with non-native consonant clusters at the single syllable level. Interestingly, posterior inferior sulcus did not show significant activation in this present study contrary to previous work, suggesting that this area may be less involved when learning new multisyllabic sequences containing previously established phonemic motor programs (i.e., familiar consonant clusters). Overall, the findings corroborate evidence that AWS present with deficits in execution, rather than motor learning, of new motor speech sequences before and after acquisition and consolidation. The planning loop, which is part of the phonological working memory system, may be relatively preserved in AWS. The results of the study contribute to our understanding of the neural correlates of speech sequencing and motor learning in people who stutter.
Topic Areas: Speech Motor Control, Disorders: Developmental