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The Concise Language Paradigm in left and right hemisphere stroke: a longitudinal EEG study
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
Vitoria Piai1, Natascha Roos1, Britta Westner2, Maria Carla Piastra3, Anil Tuladhar2, Marina Ruiter4, Roy Kessels1, Robert Oostenveld1; 1Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands, 2Radboud University Medical Center, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, the Netherlands, 3University of Twente, Faculty of Science and Technology, Technical Medical Centre, Enschede, the Netherlands, 4Radboud University, Centre for Language Studies, Nijmegen, the Netherlands
Language is a crucial feature of everyday life, which can be impaired by stroke. Yet, our knowledge about stroke-induced neuroplasticity and its contribution to language recovery remains scarce, partly resulting from differing investigation approaches. Typically, language is tested with one task, focusing on comprehension or production. Furthermore, most neuroimaging studies are based on hemodynamic measures (fMRI), lacking complementary electrophysiological findings. Importantly, both fMRI-derived and electroencephalography (EEG) signals are affected by stroke, which can invalidate results if not considered with appropriate methodology. The complex interaction of brain, lesion (size and location), behaviour, and elapsed time further complicates post-stroke investigations, requiring a multifaceted approach. In this proof-of-principle study, we employed a paradigm that taps into aspects of comprehension and production in the same task (Concise Language Paradigm, CLaP), and performed state-of-the-art EEG source reconstruction using detailed forward models based on individual MRI scans, a practice that is not yet widely adopted in the field. We recruited stroke-free individuals (N = 13) and individuals with left (LH, N = 8) or right hemisphere (RH, N = 10) stroke in the middle cerebral artery territory. We conducted a behavioral and EEG study, paired with the CLaP, combining comprehension of auditory lead-in sentences with picture naming to evaluate post-stroke language functions after two (session 1) and seven (session 2) months. Behavioral performance per session was evaluated through picture naming from the CLaP and four standardised tests (naming, aphasia, visuospatial memory, functional communication). We analyzed scalp-level EEG data through event-related potentials and time-frequency representations, statistically evaluated by cluster-based permutation tests, while source reconstruction served to identify the underlying brain areas. We used session-averaged control group results to determine bilateral regions of interest (mirrored at midline) and calculated individual laterality indices per contrast (comprehension and production) to assess changes in hemispheric dominance between sessions. The behavioral results of the LH group fit a pattern of low scores in session 1 followed by improvement over time. RH participants mainly improved visuospatial memory and functional communication. We found significant modulations of scalp-level EEG signals as a function of conditions for all comprehension and production contrasts in each group per session. The control group source-level results were in line with previous findings (e.g., comprehension in superior temporal gyrus, production in inferior parietal lobule), supporting the validity of our source localisation. For the stroke groups, we found a significant interaction between group (LH, RH) and laterality at session 1, regardless of contrast. Specifically, the majority of LH participants who were LH-dominant at 2 months post-stroke changed to RH dominance at 7 months, while LH stroke participants who were RH-dominant at 2 months showed no laterality change. In the RH group we did not find such a pattern. Our study provides a methodological example for applying state-of-the-art EEG source reconstruction to study neural activity following stroke, attested by the findings of stroke-induced laterality changes over time in line with the literature. Moreover, applying the CLaP enabled us to determine these laterality changes for both comprehension and production using a single paradigm.
Topic Areas: Methods, Disorders: Acquired