Presentation
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Recovery in Chronic Aphasia Correlates with Language Lateralization Independent of Lesion Volume
Poster E59 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Sara Pillay1, Joseph Heffernan2, Jedidiah Mathis3, Isabelle Banke4, Diane Book5, Jeffrey Binder6; 1Medical College of Wisconsin
Objective: The relationship between language laterality and recovery in post-stroke aphasia remains unclear. Greater left hemisphere activation post-stroke is typically associated with better outcomes, particularly when lesions are small to moderate in size. Leftward lateralization is also inversely correlated with lesion size, however, leaving it unclear whether leftward language lateralization is associated with recovery independent from lesion size. Methods: 17 individuals (10F, 7M, avg 52months post stroke) completed a semantic and a phonological adaptive language mapping (ALM) fMRI task. Semantic and phonological ROIs were derived from activation maps in a previous healthy control sample (Wilson et al., 2018). Lateralization index (LI) values were calculated using a multi-threshold weighted average approach (Wilke & Schmithorst, 2006) separately in semantic and phonological ROIs during the corresponding ALM tasks. LIs range from -1 to 1, with positive values indicating leftward lateralization. Individuals also completed 4 tasks outside the scanner emphasizing semantic and/or phonological processes: picture naming, silent nonword rhyme matching, nonword repetition, and semantic picture matching. Results: Mean semantic and phonological LI values were strongly left-lateralized, with substantial individual variation. The overall hemisphere and frontal semantic and phonological ROIs were positively correlated with ALM task accuracy and average difficulty level, and negatively correlated with reaction time (RT), indicating better performance with greater leftward lateralization. These relationships remained significant after the inclusion of lesion volume as a predictor, except for the correlations of semantic hemisphere ROI and semantic frontal ROI with difficulty level. The phonological LI derived from a parietal ROI was positively correlated with accuracy on nonword repetition, nonword rhyme matching, and picture naming outside the scanner. There were no correlations between any semantic LI values and accuracy on these tasks, and no correlations between semantic picture matching and any LI value. Partial correlations controlling for the effect of lesion volume revealed persistent positive correlations between the parietal ROI phonological LI and accuracy on repetition and picture naming. Interestingly, nonword repetition accuracy was negatively correlated with frontal and hemispheric semantic LI values after including lesion volume in the regression. Discussion: The results suggest that leftward lateralization is associated with better performance on both semantic and phonological tasks, even after lesion volume is taken into consideration. In general, faster, more accurate, and higher difficulty level achievement on the ALM tasks was associated with greater left lateralization in frontal and hemispheric ROIs. Greater left lateralization of phonological processing in the parietal region was associated with better repetition, silent rhyme matching, and picture naming ability, independent of lesion size. In contrast, greater left lateralization in the semantic network was associated with poorer nonword repetition, suggesting that stronger left lateralization in the semantic network is an indirect marker of greater damage to the phonological system.
Topic Areas: Disorders: Acquired,