White matter plasticity during second language learning within and across hemispheres

Abstract

Adult second language (L2) learning is a challenging enterprise inducing neuroplastic changes in the human brain. However, it remains unclear how the structural language connectome and its subnetworks change during adult L2-learning. The current study investigated longitudinal changes in white matter (WM) language networks in each hemisphere, as well as their interconnection, in a large group of Arabic-speaking adults who learned German intensively for six months. We found a significant increase in WM-connectivity within bilateral temporal-parietal semantic and phonological subnetworks and right temporal-frontal pathways mainly in the second half of the learning period. At the same time, WM-connectivity between the two hemispheres decreased significantly. Crucially, these changes in WM-connectivity are correlated with L2 performance. The observed changes in subnetworks of the two hemispheres suggest a network reconfiguration due to lexical learning. The reduced interhemispheric connectivity may indicate a key role of the corpus callosum in L2-learning by reducing the inhibition of the language-dominant left hemisphere. Our study highlights the dynamic changes within and across hemispheres in adult language-related networks driven by L2 learning.

Non-Invasive Brain Mapping Localizes Essential Language Function in Surgical Glioma Patients

“…An extensive literature on language acquisition supports this notion by routinely identifying correlated microstructural white matter changes yet likewise detecting no evidence for macrostructural rearrangement. [47][48][49] This idea provides a possible mechanistic explanation for the efficacy of TMS guided fiber tracking (standardized to the patient-specific fractional anisotropic profile) in localizing functional white matter.…”