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The roles of the bilateral MdLF and ILF in verbal effectiveness and lexical retrieval in people with post-stroke aphasia

Poster B3 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port

Joanna Sierpowska1,2*, Jo-Anne van der Sluijs1,3*, Adrià Rofes4, Vitória Piai2,5; 1Cognition and Brain Plasticity Unit, Department of Cognition, Development and Educational Psychology, Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain, 2Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands, 3European Master’s in Clinical Linguistics, University of Groningen, Groningen, The Netherlands, 4Center for Language and Cognition, University of Groningen, Groningen, The Netherlands, 5Radboud University Medical Center, Donders Institute for Brain Cognition and Behaviour, Department of Medical Psychology, Nijmegen, The Netherlands, 6* Both authors contributed equally to this work

In people with aphasia after left hemisphere stroke, neuronal responses in the right, non-dominant hemisphere were shown to relate to contextually constrained picture naming (present in the left hemisphere for controls; Piai et al., 2017). Subsequently to these findings, the splenium was suggested to have a role in this neuroplasticity. However, later research showed a similar shift of language to the contralateral hemisphere after stroke while the corpus callosum was damaged (Chupina et al., 2022). To complement our understanding of the possible contralateral functional shift at the temporal lobe level, this study focused on the plasticity of two white matter tracts: the middle longitudinal fasciculus (MdLF) and the inferior longitudinal fasciculus (ILF). The role of the MdLF in language is heavily debated in the literature, suggesting its involvement in either dorsal (Makris et al., 2013) or ventral language stream (Wong et al., 2011), or both (Saur et al., 2008). The ILF is more strongly considered to be part of the ventral stream with a role in language comprehension (Saur et al., 2008), but the extent of this involvement is debated (Duffau et al., 2013). Our primary aim was to investigate if the bilateral MdLF and ILF are involved in verbal effectiveness and in (facilitated and interfered) lexical retrieval. Secondly, we investigated if the (micro)structural measures of the tracts between individuals with post-stroke aphasia (n=21) and healthy controls (n=24) were different. Verbal effectiveness is a measure of the ability to convey a message by verbally expressing the necessary content units, and was quantified using the Amsterdam-Nijmegen Everyday Language Test (Ruiter et al., 2011). Facilitated and interfered lexical retrieval were measured in picture-word interference (Piai & Knight, 2018) and context-driven naming tasks (Piai et al., 2017). Using diffusion-weighted imaging and probabilistic tractography, interaction effects of group (matched controls vs stroke) and hemisphere were found for fractional anisotropy (FA) and mean diffusivity (MD) for both MdLF and ILF. Specifically, tracts in the left hemisphere for participants with aphasia showed lower integrity (interaction effects for MD MdLF: F(1)=12.283, p<.001; MD ILF: F(1)=11.567, p=.001). No effects of group and hemisphere were found for tract volume (p>.05). In individuals with aphasia, higher FA (ρ(15)=.55, p=.033 FDR corr.) and lower MD (ρ(15)=-.58, p=.033 FDR corr.) of the left ILF significantly correlated with higher verbal effectiveness. In addition, correlations not surviving multiple-comparisons corrections were observed between lower MD in the left MdLF and higher verbal effectiveness (ρ(15)=-.50, p=.039 uncorr.)), overall accuracy in the context-driven naming task (ρ(18)=-.45, p=.046 uncorr.), and between higher FA in the right ILF and greater naming facilitation due to constraining contexts (ρ(18)=.47, p=.035 uncorr.). These findings suggest that the left MdLF and the ILF are involved in language processing to some degree, with a more prominent role of the ILF in verbal effectiveness. Future research will combine tractography and electrophysiological data to gain insight into contralateral functional neuroplasticity.

Topic Areas: Language Production, Disorders: Acquired

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