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Neural contributions to the speech disorder in Huntington’s disease
Poster Session C, Friday, October 25, 4:30 - 6:00 pm, Great Hall 3 and 4
Elaine Kearney1,2, Matthew O'Donohue3, Katie L. McMahon3, Greig I. de Zubicaray3; 1University of Queensland, 2Princess Alexandra Hospital, 3Queensland University of Technology
Introduction. Over 90% of individuals with Huntington’s disease (HD) develop a speech disorder that has a devastating impact on their quality of life, yet little is known about the brain mechanisms underlying the speech disorder. Speech has become an important biomarker in HD, as speech changes occur in the premanifest stage (i.e., in those with the gene expansion for HD but prior to clinical diagnosis). To date, a single neuroimaging study has linked structural brain changes to speech measures in HD (Skodda et al., 2016), however, the findings were limited as the participants were not classed as having speech impairment and the study was insufficiently powered to detect effects in subcortical structures. The current work aims to identify cortical and subcortical differences in the speech production network in individuals with premanifest HD with and without speech impairment (HDSI, HDN), compared to age- and gender-matched controls (CON). Based on the Directions Into Velocities of Articulators (DIVA) model (Guenther, 2016) and pathophysiology of HD, we hypothesise that the ventral premotor cortex and basal ganglia motor loop will show atrophy in the HDSI group, compared to the HDN and CON groups. Method. Demographic, clinical, and neuroimaging data were accessed from the PREDICT-HD study, a longitudinal study of early disease prediction in premanifest HD (Paulsen et al., 2020). Speech impairment was determined based on the dysarthria question in the United HD Rating Scale (0 = no speech impairment; >=1 = speech impairment). Fifty-two individuals with premanifest HD were classed as having speech impairment and had neuroimaging data available (mean age 49.5 years +/-8.7; 27 female); an additional 52 age- and gender-matched HDN and CON participants were pseudo-randomly sampled from the larger cohort. T1-weighted images were processed using Freesurfer. Processing of the cortical data is ongoing, and cortical thickness and local gyrification index will be extracted for regions of interest in the speech production network. The subcortical and cerebellar data were automatically segmented in Freesurfer, with grey matter volume extracted for the caudate, putamen, pallidum, thalamus, and cerebellum. Group differences in grey matter volume were examined using ANCOVAs, controlling for total intracranial volume and scanner field strength. Significant main effects were evaluated using pairwise comparisons and results were FDR-corrected. Results. Both HDSI and HDN groups showed reduced grey matter volume in the caudate, putamen, pallidum, and thalamus bilaterally compared to the CON group (ps < .05, small-large effects). In addition, HDSI exhibited reduced volume in the right cerebellum, relative to the control group (p = .045, small effect), and the caudate, putamen, and pallidum bilaterally compared to the HDN group (ps < .05, medium-large effects). Conclusion. Changes in speech production in premanifest HD are primarily associated subcortically with atrophy in the basal ganglia structures of the caudate, putamen, and pallidum. These findings are in line with the DIVA account of speech production that posits that the basal ganglia motor loop is implicated in the feedforward control of speech production. Additional analyses will reveal the cortical contributions to the speech disorder in premanifest HD.
Topic Areas: Disorders: Acquired, Speech Motor Control