Abstract
PurposeBrain imaging has provided puzzle pieces in the understanding of language. In neurologically healthy populations, the structure of certain brain regions is associated with particular language functions (e.g., semantics, phonology). In studies on focal brain damage, certain brain regions or connections are considered sufficient or necessary for a given language function. However, few of these account for the effects of lesioned tissue on the “functional” dynamics of the brain for language processing. Here, functional connectivity (FC) among semantic–phonological regions of interest (ROIs) is assessed to fill a gap in our understanding about the neural substrates of impaired language and whether connectivity strength can predict language performance on a clinical tool in individuals with aphasia.MethodClinical assessment of language, using the Western Aphasia Battery–Revised, and resting-state functional magnetic resonance imaging data were obtained for 30 individuals with chronic aphasia secondary to left-hemisphere stroke and 18 age-matched healthy controls. FC between bilateral ROIs was contrasted by group and used to predict Western Aphasia Battery–Revised scores.ResultsNetwork coherence was observed in healthy controls and participants with stroke. The left–right premotor cortex connection was stronger in healthy controls, as reported by New et al. (2015) in the same data set. FC of (a) connections between temporal regions, in the left hemisphere and bilaterally, predicted lexical–semantic processing for auditory comprehension and (b) ipsilateral connections between temporal and frontal regions in both hemispheres predicted access to semantic–phonological representations and processing for verbal production.ConclusionsNetwork connectivity of brain regions associated with semantic–phonological processing is predictive of language performance in poststroke aphasia. The most predictive connections involved right-hemisphere ROIs—particularly those for which structural adaptions are known to associate with recovered word retrieval performance. Predictions may be made, based on these findings, about which connections have potential as targets for neuroplastic functional changes with intervention in aphasia.Supplemental Material https://doi.org/10.23641/asha.12735785
Highlights
The presence of statistically significant connections in the persons with aphasia (PWAs) and control groups suggests that these regions of interest (ROIs) represent an intrinsically coherent network that is present at rest in healthy and lesioned brains
The network of semantic and phonological brain regions chosen as ROIs for their roles in semantic and phonological processing show patterns of functional connectivity (FC) that predict language performance in poststroke aphasia
Other connections involved frontal regions and were largely left lateralized, with the exception of the right posterior middle temporal gyrus (pMTG)–right inferior frontal gyrus (IFG), which was predictive of aphasia severity and word retrieval for verbal production
Summary
An existing data set was used for the study, which included 31 right-handed, chronic left-hemisphere stroke participants with aphasia (New et al, 2015). Fifteen of the participants had comorbid apraxia of speech (AOS; see New et al, 2015, for more details). All participants were 18–75 years of age, right-handed, self-reported (by PWA or caregiver) proficient English speakers prior to the stroke, and had no contraindications for undergoing an MRI. The examiner, a qualified speech-language pathologist, walked through the participant information statement and consent form with the participant and caregiver and asked comprehension questions to ensure understanding of study details prior to obtaining written consent. Because the assessments included verbal expression, participants were excluded if they had AOS judged as severe, as described below
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