Absence of Perilesional Neuroplastic Recruitment in Chronic Poststroke Aphasia

Abstract

Background and ObjectivesA prominent theory proposes that neuroplastic recruitment of perilesional tissue supports aphasia recovery, especially when language-capable cortex is spared by smaller lesions. This theory has rarely been tested directly, and findings have been inconclusive. Here, we test the perilesional plasticity hypothesis using two fMRI tasks in two groups of patients with prior aphasia diagnosis.MethodsTwo cohorts totaling 82 chronic left-hemisphere stroke patients with prior aphasia diagnosis, and 82 control participants underwent fMRI using either a naming task or a reliable semantic decision task. Individualized perilesional tissue was defined by dilating anatomical lesions, and language regions were defined using meta-analyses. Mixed modeling examined differences in activity between groups. Relationships with lesion size and aphasia severity were examined.ResultsPatients exhibited reduced activity in perilesional language tissue relative to controls in both tasks. Although a few cortical regions exhibited greater activity irrespective of distance from the lesion, or only when distant from the lesion, no regions exhibited increased activity only when near the lesion. Larger lesions were associated with reduced language activity irrespective of distance from the lesion. Using the reliable fMRI task, reduced language activity related to aphasia severity independent of lesion size.DiscussionWe find no evidence for neuroplastic recruitment of perilesional tissue in aphasia beyond its typical role in language. Rather, our findings are consistent with alternative hypotheses that changes in left-hemisphere activation during recovery relate to normalization of language network dysfunction and possibly recruitment of alternate cortical processors. These findings clarify left-hemisphere neuroplastic mechanisms supporting language recovery after stroke.

Individualized functional localization of the language and multiple demand network in chronic post-stroke aphasia

“…Additionally, understanding the role of spared left-hemispheric tissue in language recovery requires considering inter-individual variability and comparing to baseline activity in healthy controls. A recent study found no support for the perilesional neuroplastic recruitment hypothesis in aphasia, i.e., no enhanced activity in brain areas surrounding individual lesions, but some evidence supporting recruitment of brain regions distant to the lesion (DeMarco et al, 2022). Further studies employing individualized approaches, to investigate language network reorganization, treating individual differences as a variable of interest, are imperative in understanding language network reorganization in aphasia (Seghier and Price, 2018).…”

“…Most research in aphasia focused on the chronic stage (>6 months) post-stroke, characterized by a more stable language profile in IWA (Johnson et al, 2019). Both longitudinal and cross-sectional studies predominantly indicate optimal language recovery through normalization of activation in the left-hemispheric language network (Warren et al, 2009; Crinion et al, 2006; DeMarco et al, 2022; Saur et al, 2006; Stockert et al, 2020; Szaflarski et al, 2011, 2013; Griffis et al, 2017b; Fridriksson, 2010; Pillay et al, 2018; Wilson and Schneck, 2021; Li et al, 2022). The preservation of lesion-free tissue in left hemisphere language regions emerges as a crucial factor in facilitating language recovery (Fridriksson, 2010; Griffis et al, 2017a; Sims et al, 2016; Wilson and Schneck, 2021).…”