Poster Slam Session A, Tuesday, August 20, 2019, 10:00 – 10:15 am, Finlandia Hall, Michal Ben-Shachar
BDNF Genotype Specific Differences in Cortical Activation in Chronic Aphasia
Sigfus Kristinsson1, Grigori Yourganov2, Feifei Xiao3, Leonardo Bonilha4, Brielle C. Stark5, Chris Rorden2, Basilakos Alexandra1, Julius Fridriksson1;1Department of Communication Sciences & Disorders, University of South Carolina, 2Department of Psychology, University of South Carolina, 3Department of Epidemiology and Biostatistics, University of South Carolina, 4Department of Neurology, Medical University of South Carolina, 5Department of Speech and Hearing Sciences, Indiana University
Introduction: The presence of a Met allele at one or both codon positions 66 of the BDNF gene has been associated with poorer functional recovery and decreased functional brain activation in stroke patients (Johansson, 2011; Kim et al., 2016). The current study aimed to explore functional brain activation by BDNF genotype in individuals with chronic aphasia. We hypothesized that the presence of the Met allele of the BDNF gene is associated with reduced functional brain activation compared to individuals without the Met allele polymorphism. Methods: We recruited 87 individuals with chronic stroke-induced aphasia (typical BDNF genotype (Val66Val): n=53 (61%), atypical BDNF genotype (Val66Met/Met66Met): n=34 (39%)). Participants performed a naming task during fMRI scanning in which they were presented with 40 colored pictures of high-frequency nouns. For the purpose of establishing a baseline for the fMRI data analysis, 20 colored abstract pictures were shown at random among the real picture presentation. We utilized general linear modeling and a standard hemodynamic response function to generate contrast maps isolating brain activation related to naming. We then obtained the number of voxels where naming-related brain activation was significantly greater than zero (FWE=.05) for each group and compared across groups using independent samples t-test. Neuropsychological testing was conducted to compare language impairment between BDNF genotype groups and WAB-AQ was used as a covariate in the analysis. Results: Participants in both genotype groups presented with distributed cortical and subcortical lesions that covered the middle cerebral artery territory. Greatest lesion overlap was identified in the longitudinal fasciculus (MNI coordinates: -34x-36x28) in the typical genotype group and the longitudinal fasciculus (MNI: -36x-8x25) and the insula (MNI: -44x-9x3) in the atypical genotype group. The overall activation pattern was similar across groups, with greatest intensity of activation present in the bilateral posterior temporal gyrus, pre- and postcentral gyrus, and the longitudinal fissure. We found that the number of activated voxels was greater in the typical genotype group compared to the atypical group at the whole brain level (98,500 vs. 28,630; t(85)=18.63, p<.001), in the left hemisphere (37,290 vs. 7,000; t(85)=8.33, p<.001), and in the right hemisphere (74,830 vs. 30,630; t(85)=11.29, p<.001). Corresponding to results from functional MRI data analysis, we observed clear differences in language impairment between the typical and atypical BDNF genotype groups, where aphasia severity was significantly greater in the atypical compared to the typical group (WAB-R AQ: 54.3 vs. 64.2, p=.033; PNT: 52.8 vs. 74.7, p=.047, respectively). Conclusion: While consistent with previous findings in the stroke population (Johansson, 2011; Kim et al., 2016), conflicting results have been reported in acute aphasia (e.g., De Boer et al., 2017; Mirowska-Guzel et al., 2013). Given the subtle effects of BDNF genotype on BDNF secretion (18-30% decrease), our results may suggest that the effects of genotype accumulate over time in the recovery process, enabling individuals with the typical genotype to experience greater recovery than their counterparts with the atypical genotype.
Themes: Disorders: Acquired, Language Genetics
Method: Functional Imaging
Poster A1