Abstracts

Rationale: Left mesial temporal sclerosis (MTS) patients show impaired naming on language testing. Functional reorganization of language may represent a compensatory mechanism. It is unclear if reorganization is associated with improved language performance.Methods: To evaluate if atypical language dominance is associated with better language performance in left unilateral MTS patientsResults: We studied 22 left MTS patients and 12 healthy controls (C). Subjects were right-handed, aged between 18 and 55 years with at least eight years of education. Subjects underwent an object naming language task. Eight patients showed impaired performance, defined as 1.5 or more standard deviations (SD) below controls’ performance. Fourteen patients had normal performance, defined as ≥ than -1.5 SD compared to controls. All subjects underwent an fMRI reading responsive naming (RRN) paradigm. Data were acquired with 3T MRI scanner, compressed GRE EPI BOLD images, (40 AC/PC oriented slices, 3mm3 isotropic voxels, RT=2s, ET=30ms) and processed with FSL package (Oxford University, UK), nonparametric statistical inference. Between groups analysis was performed with ANOVA with p<0.05 significance level. Six language regions of interest (ROIs) were defined for each hemisphere on aparc.a2009: inferior frontal (IFG), middle frontal (MFG), superior frontal (SFG), inferior temporal (ITG), middle temporal (MTG), and superior temporal (STG) gyri. A language lateralization index (LI) was obtained for each ROI with a threshold-independent method using a bootstrap algorithm. LI was calculated as (left - right activated voxels) / (left + right activated voxels). Statistical analysis compared LI indices in each group for each ROI with t-tests. We also evaluated correlation between subjects’ object naming task performance with their in-scan performance during the RRN paradigm using Spearman correlation.Conclusions: In the RRN fMRI paradigms, lower LIs, indicative of left-to-right language reorganization in the frontal regions and in the medial temporal gyrus, were associated with better performance on naming tasks. Reorganization of language networks appears to be a successful mechanism to preserve language function.