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What Can Glioma Patients Teach Us about Language (Re)Organization in the Bilingual Brain: Evidence from fMRI and MEG
Poster D49 in Poster Session D with Social Hour, Friday, October 7, 5:30 - 7:15 pm EDT, Millennium Hall
Ileana Quinones1, Lucia Amoruso1,2, Iñigo Pomposo3,5, Santiago Gil-Robles3,4, Manuel Carreiras1,2,6; 1Basque Center on Cognition, Brain and Language, 2IKERBASQUE. Basque Foundation for Science, 48009 Bilbao, Spain, 3BioCruces Research Institute, 48015 Bilbao, Spain, 4Department of Neurosurgery, Hospital Quironsalud, 28223 Madrid, Spain, 5Department of Neurosurgery, Hospital Cruces, 48903 Bilbao, Spain, 6University of the Basque Country, UPV/EHU, 48940 Bilbao, Spain
A remarkable feature of the central nervous system is its inherent capacity to dynamically reorganize its structure and function depending on the environment 1-5. Recent evidence suggests that the presence of brain tumors (e.g., low-grade gliomas) triggers language reorganization 3,6-9. Neuroplasticity mechanisms called into play can transfer linguistic functions from damaged to healthy areas unaffected by the tumor 3,6-9. This phenomenon has been reported in monolingual patients, but much less is known about the neuroplasticity of language in the bilingual brain. A central question is whether processing a first or second language involves the same or different cortical territories and whether damage results in diverse recovery patterns depending on the language involved. This question becomes critical for preserving language areas in bilingual brain tumor patients so as to prevent involuntary pathological symptoms following resection. In the current study, we combined the high spatial resolution of fMRI with the high temporal resolution and oscillatory information provided by MEG to map the language network and its functional (re)organization in the bilingual brain, both prior to and following tumor-removal surgery. Specifically, we tested five Spanish-Basque bilingual patients with low-grade gliomas before and four months after surgery for tumor resection, evaluating their neural capacity to negotiate L1 (Spanish) and L2 (Basque) language information before and after the resection of critical language-hubs. This longitudinal approach (post vs. pre-surgery) granted us a unique opportunity to estimate functional neuroplasticity at the individual level considering patient’s cognitive status both prior to and following tumor removal surgery. We present three main findings. First, all patients preserved linguistic function in both languages after surgery suggesting that the surgical intervention, together with the intra-operative language mapping, were successful in preserving cortical and subcortical structures necessary to allow brain plasticity at the functional level. Second, we found reorganization of the language network after tumor resection in both languages, mainly reflected by a shift of activity to right hemisphere nodes and by the recruitment of ipsilesional left nodes. Third, we found that this reorganization varied according to the language involved, indicating that L1 and L2 follow different reshaping patterns after surgery. Importantly, these effects were observed with both fMRI and MEG. Our fMRI-MEG findings suggest that language reorganization takes place in the bilingual brain after tumor resection following neuroplasticity mechanisms similar to those observed in monolingual patients (i.e., recruitment of frontal ipsilesional and contralesional nodes). Furthermore, they show that this language rearrangement occurs in both the L1 and L2, underscoring the necessity of mapping all the languages that a patient speaks. Finally, they also hint at differential post-surgery reorganization of L1 and L2, suggesting that distinct languages may not completely overlap in terms of their neural representation or, alternatively, that the changes necessary to preserve function engage different networks depending on language proficiency. Overall, from a clinical standpoint, these findings help delineate personalized surgical strategies that respect a patient’s linguistic profile in order to preserve language function in an integral fashion.
Topic Areas: Disorders: Acquired, Multilingualism