Language impairments and their neuroanatomical correlates in patients after brain tumor resection
The current study is the first to examine language deficits induced by resection of a brain tumor in Russian-speaking patients and the first in general to employ multimodal neuroimaging (voxel-based lesion-symptom mapping and tractography) to investigate the neural underpinnings of the observed deficits. During the first year of the project, we collected behavioral and neuroimaging (MRI) data in 35 patients bearing primary brain tumor, at two time points: prior to surgery and during the first week after surgery. We first made pairwise comparisons between the behavioral scores obtained in the RAT subtests before and after surgery and found a significant difference in most of the subtests (with the exception of non-word discrimination and lexical decision subtests). Moreover, postoperative deficit was more pronounced in language production compared to comprehension. Finally, in the subtests tapping into language production, higher linguistic level was associated with greater degree of language impairment, that is, language production was more impaired at the sentence level compared to the lexical and phonological levels. Patients’ behavioral data were then analyzed in conjunction with MRI data. Voxel-based lesion symptom mapping analysis yielded a significant cluster of voxels in the left temporal pole associated with postoperative language comprehension deficits. Language production deficits, on the other hand, were associated with damage to ventral premotor cortex and insular lobe. We reconstructed long-range associative white matter pathways and explored the correlations between the changes in their diffusion metrics before and after surgery with the behavioral data. We found that damage to the long segment of the arcuate fasciculus predicts worse postoperative language production performance. Interestingly, we observed a positive correlation between the volume of the left frontal aslant tract and the discourse production scores; however, this correlation did not remain significant once a correction for multiple comparisons was applied. We did not find any significant correlations between postoperative language comprehension deficits and changes in the diffusion metrics of the reconstructed white matter tracts. The obtained results are in general agreement with the current models of neural organization of language, but provide new valuable insights into the neural underpinnings of language.
The project was supported by RFBR grant № 18-012-00829 (2018 - 2020), the head - Olga Dragoy
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