FV 13 Electrophysiological correlates of language recovery – an MEG study of neuroplasticity in chronic post stroke aphasia
2017
Background Previous studies have demonstrated that efficient language and communication therapy in chronic post stroke aphasia leads to significant clinical language improvements (Pulvermuller et al., 2001) and promotes neuroplasticity. Brain areas frequently associated with functional restitution of language comprise perilesional sites in the left hemisphere (MacGregor et al., 2015) as well as right-hemispheric regions, homotopic to those lesioned in the left (Mohr et al., 2014). To date, however, the neuronal mechanisms underlying therapy-induced language changes and functional restitution are still largely unclear. In the present study, hemispheric contributions to neuroplasticity and neurophysiological changes were investigated in chronic aphasia patients by using magnetoencephalography. Methods Patients underwent intensive language action therapy for three hours per day on 10 consecutive week-days. Before and immediately after treatment, language and communication skills were assessed and patients' brain responses were recorded during automatic language processing, employing a lexical magnetic mismatch negativity (MMNm) paradigm, in which words and meaningless pseudowords were presented auditorily. Results After the two-week therapy interval, patients showed significant clinical improvements of language skills, as assessed by the Boston Diagnostic Aphasia Examination. Spatio-temporal dynamics of neuronal changes revealed a significant increase in word-specific neuro-magnetic MMNm activation around 200ms after stimulus identification points. This neuromagnetic enhancement of the MMNm brain response occurred specifically for words and was most prominent over perilesional areas in the left hemisphere. Importantly, therapy-induced changes in neuromagnetic activation to words significantly correlated with clinical test performance. Discussion and conclusion The results suggest that language recovery in chronic post stroke aphasia is associated with neuroplastic changes in both cerebral hemispheres. During automatic language processing, particularly perilesional regions in the left-hemisphere seem to contribute to functional restitution in patients with chronic aphasia.
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