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Residual language activation modulates naming error types in chronic post-stroke aphasia
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
Elizabeth J. Anderson1, Ryan Staples1, Andrew T. DeMarco1, Peter E. Turkeltaub1,2; 1Georgetown University Medical Center, 2MedStar National Rehabilitation Hospital
Introduction: Lexical retrieval is commonly impaired following left-hemisphere stroke. The prevalence of resultant naming errors – such as semantic errors, phonological errors, and perseverations – varies considerably across individuals. Prior research has identified key neural regions where lesion damage impairs lexical retrieval subprocesses that might contribute to different error types, including the left inferior frontal gyrus (IFG), middle temporal gyrus (MTG), and anterior/posterior inferior temporal gyri (a/pITG). Yet, error types likely also rely on functional language activation or disfunction beyond the lesion boundary. The current study analyzes error production in picture naming (1) as a function of anatomical lesion damage and (2) fMRI language activation in a large cohort of left-hemisphere stroke survivors with aphasia. Methods: 80 individuals with left-hemisphere stroke-induced aphasia participated in an adaptive fMRI semantic decision task with two alternating conditions: semantic decision (e.g., CALENDAR-DATE) versus pseudofont matching (e.g., ʖƱʖdD-ʖƱʖdD). Four regions of interest were identified based on peaks of activity in 15 controls. Naming was assessed on a set of 120 line drawings and scored for overall accuracy, semantic errors, phonological errors, and perseverations. For each ROI, two sets of Spearman partial correlations examined overall accuracy and errors as a function of (1) the proportion of the ROI lesioned (covariates: age, education, lesion volume, and apraxia severity) and (2) the language activation (covariates: age, education, lesion volume, apraxia severity, and proportion of voxels lesioned in that ROI). The analyses were corrected for multiple comparisons using the Benjamini-Hochberg method. Results: Overall naming accuracy decreased with lesion damage to the STS/MTG, aITG, and pITG and increased with higher activation of the STS/MTG and the aITG. Higher activation in the IFG and aITG correlated with fewer semantic errors. Greater lesion damage to the STS/MTG, aITG, and pITG correlated with an increase in phonological errors, whereas greater lesion damage to the IFG correlated with fewer phonological errors. Higher activation in the STS/MTG and aITG correlated with fewer perseverations. Discussion: These results link specific error types in picture naming to both lesion location and functional activation in individuals with aphasia. Lexical retrieval thus appears to rely on a distributed network of regions, with frontal and temporal regions contributing to different stages of the naming process. Activation in the aITG correlated with a decrease in every error type, suggesting it plays a general role in semantic processing and lexical retrieval. IFG activation suppresses semantic errors, likely reflecting its role in semantic interference resolution during naming. The findings for posterior temporal regions are most consistent with a role in lexical phonological retrieval. These findings demonstrate that combining lesion and activation data may better characterize the neural mechanisms underlying naming impairment. In turn, this approach may inform more individualized, brain-based approaches to aphasia treatment.
Topic Areas: Disorders: Acquired, Language Production