Voxel-based morphometry: comparison of gray matter and white matter tissue-classified maps of phoneticians and nonphoneticians | Whole brain | Probability of gray and of white matter | Exploratory first step | Greater probability of white matter in right HG (t = 3.34; PFWE-co = 0.05, small-volume correction) and just posterior to left HG (t = 2.80; p < 0.005 uncorrected) in phoneticians compared to controls (Fig. 1) |
Macroanatomical labeling a. Group difference b. Correlations with years of phonetic transcription training within phoneticians group | Left and right transverse gyri | Volume Gross morphology | To elucidate above VBM results Previous studies showing larger left Heschl's gyrus and greater left transverse gyrus splitting/duplication in faster compared to slower phonetic learners | a. Larger left (t(31) = 2.02, p < 0.05) and right (t(31) = 3.07, p < 0.005) transverse gyri in phoneticians compared to controls (Figs. 2, 3) Phoneticians are more likely to have multiple or split left (t(31) = 2.39, p < 0.01) but not right (t(31) = 0.19, p > 0.05) transverse gyri than controls (Fig. 4) b. No relationship between phonetic training and left or right transverse gyrus volumes or degree of transverse gyrus splitting within the phoneticians group |
Automatic measure of local gyrification | Left and right transverse gyri | Mean curvature | To further confirm above gross morphology results | Trend towards less right > left asymmetry in local gyrification the phoneticians compared to controls (t(31) = 1.49, p = 0.07) |
Automatic segmentation and labeling: a. Group difference b. Correlations with years of phonetic transcription training within phoneticians group | Left pars opercularis Left supramarginal gyrus | Gray matter volume Surface area | Known involvement in phonological processing Previous findings that structure left prefrontal and inferior parietal cortices in part predict phonetic processing in healthy controls | a. Larger left pars opercularis volume in phoneticians compared to non-experts (t(31) = 2.02, p < 0.05, Bonferroni correction) b. Years of transcription training predicts the surface area of the left pars opercularis (r = 0.64, p < 0.01, Bonferroni correction) Similar trend for volume of the left pars opercularis (r = 0.49, p = 0.03) (Fig. 5) |