Emily Dvorak1, James Sumowski2
1Teachers College, Columbia University, 2Icahn School of Medicine At Mount Sinai
Objective:
To investigate whether objective word-finding performance was related to thinning in the left posterior superior temporal gyrus (pSTG)/supramarginal gyrus (SMG), and whether phonemic processing mediates this relationship.
Background:
Word-finding difficulty is the most prevalent cognitive complaint in persons with MS but there is little research into this deficit or it’s neuroanatomical correlates. Recent imaging research showing disease-related changes in the left posterior superior temporal gyrus (pSTG)/supramarginal gyrus (SMG), which have elsewhere been implicated in phonological code retrieval, may shed light into a possible mechanism for word-finding deficits in MS.
Design/Methods:
Objective language performance in persons with relapse-onset MS (n=135) was assessed with our validated measure of objective word-finding, semantically-cued retrieval of precise targets (SCRPT). Phonemic processing (PP) ability was also assessed. Objective performance was adjusted for age, sex, and receptive vocabulary. Freesurfer was used to derive 180 ROIs (Human Connectome Project) of cortical thickness in the left hemisphere from high resolution T1-weighted MR images, which were adjusted for mean cortical thickness. Correlations investigated relationships between objective word-finding and cortical thickness across ROIs, adjusting for multiple comparisons. Additionally, mediation analysis investigated whether PP explains the relationship between objective word-finding and identified ROIs.
Results:
Of the 180 ROIs, Perisylvian Language area (PSL), located in the posterior STG/SMG region, was the only area related to SCRPT after adjusting for multiple comparisons (r=0.32, p=0.0001, FDR-adjusted p=0.030). Performance on PP partially mediated the relationship between SCRPT and PSL thickness (mediation effect: 0.064 [0.010, 0.153]; total effect: 0.254 [0.102, 0.407]; direct effect: 0.190 [0.041, 0.340]), explaining 25.1% of the relationship.
Conclusions:
Results suggest that changes in posterior STG/SMG contribute to word-finding deficits in persons in MS. In line with research highlighting this region’s importance in phonological code retrieval, phonemic processing ability, which could be impacted by such thinning, may underlie word-finding decline in MS.