Abstract
Purpose Understanding the brain basis of language and cognitive outcomes is a major goal of aphasia research. Prior studies have not often considered the many ways that brain features can relate to behavioral outcomes or the mechanisms underlying these relationships. The purpose of this review article is to provide a new framework for understanding the ways that brain features may relate to language and cognitive outcomes from stroke. Method Brain-behavior relationships that may be important for aphasia outcomes are organized into a taxonomy, including features of the lesion and features of brain tissue spared by the lesion. Features of spared brain tissue are categorized into those that change after stroke and those that do not. Features that change are further subdivided, and multiple mechanisms of brain change after stroke are discussed. Results Features of the stroke, including size, location, and white matter damage, relate to many behavioral outcomes and likely account for most of the variance in outcomes. Features of the spared brain tissue that are unchanged by stroke, such as prior ischemic disease in the white matter, contribute to outcomes. Many different neurobiological and behavioral mechanisms may drive changes in the brain after stroke in association with behavioral recovery. Changes primarily driven by neurobiology are likely to occur in brain regions with a systematic relationship to the stroke distribution. Changes primarily driven by behavior are likely to occur in brain networks related to the behavior driving the change. Conclusions Organizing the various hypothesized brain-behavior relationships according to this framework and considering the mechanisms that drive these relationships may help investigators develop specific experimental designs and more complete statistical models to explain language and cognitive abilities after stroke. Eight main recommendations for future research are provided. Presentation Video https://doi.org/10.23641/asha.10257578.
Highlights
Understanding the brain basis of language and cognitive outcomes is a major goal of aphasia research
I hope that the organizational framework and mechanisms for brain–behavior relationships described in this review article will aid researchers to design experiments that consider as many relevant brain variables as possible and to test increasingly specific hypotheses of how and why brain features relate to outcomes after stroke
After accounting for features of the stroke itself, which likely explain most of the variance in outcomes, remaining explainable variance in aphasia outcomes must relate to features of the spared brain tissue
Summary
Purpose: Understanding the brain basis of language and cognitive outcomes is a major goal of aphasia research. Many studies have been published associating language or cognitive outcomes from stroke with brain factors such as stroke size and location (e.g., Thye & Mirman, 2018) or activity in brain regions spared by stroke (e.g., Fridriksson, Bonilha, Baker, Moser, & Rorden, 2010) These types of studies often describe how brain features relate to aphasia outcomes without fully considering the biological and behavioral mechanisms underlying these relationships. I hope that the organizational framework and mechanisms for brain–behavior relationships described in this review article will aid researchers to design experiments that consider as many relevant brain variables as possible and to test increasingly specific hypotheses of how and why brain features relate to outcomes after stroke
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