Understanding Language Reorganization With Neuroimaging: How Language Adapts to Different Focal Lesions and Insights Into Clinical Applications

Abstract

When the language-dominant hemisphere is damaged by a focal lesion, the brain may reorganize the language network through functional and structural changes known as adaptive plasticity. Adaptive plasticity is documented for triggers including ischemic, tumoral, and epileptic focal lesions, with effects in clinical practice. Many questions remain regarding language plasticity. Different lesions may induce different patterns of reorganization depending on pathologic features, location in the brain, and timing of onset. Neuroimaging provides insights into language plasticity due to its non-invasiveness, ability to image the whole brain, and large-scale implementation. This review provides an overview of language plasticity on MRI with insights for patient care. First, we describe the structural and functional language network as depicted by neuroimaging. Second, we explore language reorganization triggered by stroke, brain tumors, and epileptic lesions and analyze applications in clinical diagnosis and treatment planning. By comparing different focal lesions, we investigate determinants of language plasticity including lesion location and timing of onset, longitudinal evolution of reorganization, and the relationship between structural and functional changes.

Brain Functional Connectivity in Low- and High-Grade Gliomas: Differences in Network Dynamics Associated with Tumor Grade and Location

“…Brain tumors are disruptive lesions that lead to functional modifications of brain networks, known as functional reorganization or plasticity [ 1 ]. Short- and long-range effects have been shown using task-based and resting-state fMRI in patients with gliomas [ 2 ], possibly representing an adaptive phenomenon to compensate for tumor-induced clinical deficits.…”

Reorganization and Plasticity of the Language Network in Patients with Cerebral Gliomas

“…Searches included the key words “tumor” AND “language” AND “plasticity” OR “reorganization”. Additionally, previous reviews ( Cargnelutti et al, 2020a , Cirillo et al, 2019 , Krishna et al, 2021 , Pasquini et al, 2022 ) and references from included studies were screened for further articles. The search in PubMed yielded a total of 35.178 results.…”

“…These previous attempts include comparisons between pre- and intraoperative mapping techniques for motor and language functions in patients with gliomas ( Cirillo et al, 2019 ), investigations of white matter connectivity, and the role of the contralesional hemisphere in language function ( Cargnelutti et al, 2020a ), as well as mechanisms of aphasia recovery in glioma patients ( Krishna et al, 2021 ). Another review focused on the comparisons of plasticity mechanisms in the language network across different focal lesions ( Pasquini et al, 2022 ).…”

Language Network Dysfunction and Formal Thought Disorder in Schizophrenia

“…LN shows a particular capacity for plastic adaptation to damage, in part due to a high degree of degeneracy in representation that confers robustness to damage [98]. The adaptive changes in LN are apparent during the normal ageing process where despite sensorimotor decline, language processing remains stable with novel brain regions recruited in its service [99], and after vascular damage, where non-dominant homologues come into play [100].…”