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Lesions and language activity in post-stroke aphasia too mild to detect on the Western Aphasia Battery-Revised
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Poster A56 in Poster Session A, Tuesday, October 24, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Alycia Laks1,2, Andrew DeMarco1, Sara Dyslin1, Peter Turkeltaub1,2; 1Center for Brain Plasticity and Recovery, Georgetown University, Washington, DC, USA, 2Research Division, MedStar National Rehabilitation Hospital, Washington, DC, USA
Introduction: Some left hemisphere (LH) stroke survivors are identified as not having aphasia on the Western Aphasia Battery-Revised (WAB-R; Kertesz, 2007), despite self or caregiver reports of communication deficits (Cavanaugh & Haley, 2020). While research on this “not aphasic by WAB” (NABW) group is limited, prior studies have found differences between this group and healthy controls on behavioral testing (Armstrong et al., 2013, Dalton & Richardson, 2015; Fromm et al., 2017). Fromm et al. (2017) also compared the NABW group to the top anomic (TA) group with the same WAB Aphasia Quotient (AQ) range of 6.2 (NABW AQ=93.8-100; TA=87.5-93.7) and found group differences in discourse measures. The limited research on the NABW group leaves open questions about the nature of their impairments and stroke lesions compared to people identified as having aphasia on the WAB. Here we analyzed group data to identify differences between the NABW and TA groups on behavioral testing, lesion size and location, and fMRI language activation. Methods: Participants were 38 LH stroke survivors (18TA, 20NABW; Age=63.2y (11.8); Gender=19F, 19M; Race=14 Black, 24 White; Education=16.9y (2.6); Chronicity=51.1m (68.7)). NABW participants had self or caregiver reported aphasia. All participants completed an MRI and language battery. We performed Independent Samples T-Tests and Chi-squared tests to determine group differences on behavioral testing scores and demographics variables. Lesions were manually traced from FLAIR and T1-weighted scans and warped to MNI space. Support Vector Regression Lesion-Symptom Mapping (SVR-LSM) was applied to determine differences in lesion location between groups (DeMarco and Turkeltaub, 2018). Lesion volume was regressed out of lesion data and 10,000 permutations were used to control the cluster-level family-wise error rate. Participants performed an adaptive semantic decision fMRI task (Wilson, 2018) to localize active language regions. We then performed a mass-univariate t-test comparing activation magnitude (SEM>VIS) between the NABW and TA groups. The results were thresholded voxelwise p<.005 and corrected for cluster size p<.05 based on 5000 permutations. Results: There were no significant group differences in demographic variables or lesion volume (p=.17). There were significant group differences in WAB subtest performance on Spontaneous Speech (p<.001), Repetition (p<.001), and Word Finding (p<.001), but not Auditory Verbal Comprehension (p=.55). Eight of 14 behavioral tasks had group differences, including measures of semantics, phonology, and reading. There were no significant findings in the lesion-symptom map, but there was a gradient effect with superior frontal lesions associated with NABW and posterior superior temporal lesions associated with TA. In the fMRI data, we found greater activation in the ventral IFG for the NABW group compared to the TA group at the voxelwise cutoff, though the difference did not survive statistical correction at the cluster level. Conclusion: These results indicate that there are behavioral differences between the NABW and TA groups beyond what can be captured with the WAB. While no statistically significant differences were found in lesion volume, location, or language activation to explain the differences on behavioral testing, there were trending differences that might require a larger sample size to confirm statistically.
Topic Areas: Disorders: Acquired,