Predicting hemispheric dominance for language production in healthy individuals using support vector machine

We used a Support Vector Machine (SVM) classifier to assess hemispheric pattern of language dominance of 47 individuals categorized as non‐typical for language from their hemispheric functional laterality index (HFLI) measured on a sentence minus word‐list production fMRI‐BOLD contrast map. The SVM classifier was trained at discriminating between Dominant and Non‐Dominant hemispheric language production activation pattern on a group of 250 participants previously identified as Typicals (HFLI strongly leftward). Then, SVM was applied to each hemispheric language activation pattern of 47 non‐typical individuals. The results showed that at least one hemisphere (left or right) was found to be Dominant in every, except 3 individuals, indicating that the “dominant” type of functional organization is the most frequent in non‐typicals. Specifically, left hemisphere dominance was predicted in all non‐typical right‐handers (RH) and in 57.4% of non‐typical left‐handers (LH). When both hemisphere classifications were jointly considered, four types of brain patterns were observed. The most often predicted pattern (51%) was left‐dominant ( Dominant left‐hemisphere and Non‐Dominant right‐hemisphere), followed by right‐dominant (23%, Dominant right‐hemisphere and Non‐Dominant left‐hemisphere) and co‐dominant (19%, 2 Dominant hemispheres) patterns. Co‐non‐dominant was rare (6%, 2 Non‐Dominant hemispheres), but was normal variants of hemispheric specialization. In RH, only left‐dominant (72%) and co‐dominant patterns were detected, while for LH, all types were found, although with different occurrences. Among the 10 LH with a strong rightward HFLI, 8 had a right‐dominant brain pattern. Whole‐brain analysis of the right‐dominant pattern group confirmed that it exhibited a functional organization strictly mirroring that of left‐dominant pattern group. Hum Brain Mapp 38:5871–5889, 2017 . © 2017 Wiley Periodicals, Inc.