The gyrification pattern of Heschl’s gyrus (HG) and manual delineation of the planum temporale (PT) on individual images.

(A) Examples of three types of HG gyrification patterns (red line): single HG (sHG), common stem duplication (CSD), and complete duplication (CPD). HG1, the anterior part of duplicated HG; HG2, the posterior part of duplicated HG; SI, the sulcus intermedius; HS1, the anterior Heschl’s sulcus; HS2, the posterior Heschl’s sulcus. (B) An example of manually delineated PT on a T1-weighted image (blue line) and reconstructed 32k~ pial surface (blue area). The oblique section plane (red dotted line) was applied to expose the internal surface of the superior temporal gyrus using the Anatomist 42.

The reliability of PT measures from manually delineated PT

The distribution of HG gyrification patterns

PT functional asymmetry of speech processing at the group level.

L1/R1, single HG on the left and single HG on the right; L1/R2, single HG on the left and duplicated HG on the right; L2/R1, duplicated HG on the left and single HG on the right; L2/R2, duplicated HG on the left and duplicated HG on the right. * denotes Significant difference between left and right PTs (i.e., PFWE < 0.05). Positive and negative values of the asymmetry index represent leftward and rightward asymmetry, respectively.

PT structural asymmetry at the group level.

L1/R1, single HG on the left and single HG on the right; L1/R2, single HG on the left and duplicated HG on the right; L2/R1, duplicated HG on the left and single HG on the right; L2/R2, duplicated HG on the left and duplicated HG on the right. NDI, neurite density index; ODI, orientation dispersion index. * denotes significant difference between left and right PTs (PFWE < 0.05). Positive and negative values of the asymmetry index represent leftward and rightward asymmetry, respectively.

Interindividual correlation of PT functional and structural asymmetries.

The correlation of the AI of speech comprehension activation and the AI of myelin content showed significant dependence on the gyrification pattern of HG (i.e., a significant interaction with the group factor); therefore, scatter plots for their correlations within the 4 groups were displayed separately. L1/R2, single HG on the left and duplicated HG on the right; L2/R1, duplicated HG on the left and single HG on the right; L2/R2, duplicated HG on the left and duplicated HG on the right. For the other pairs of functional and structural AIs, the gyrification pattern of HG showed no significant effect on their correlations. The scatter plots for nonsignificant correlations (PFWE > 0.05) are colored gray. AI, asymmetry index; NDI, neurite density index; ODI, orientation dispersion index; ns, non-significant. * denotes significant correlation in this group.

Interindividual functional-structural correlations of the left and right PT.

The correlation of speech comprehension activation and myelin content for the left PT showed significant dependence on the gyrification pattern of HG (i.e., a significant interaction with the group factor); therefore, scatter plots for their correlations within the 2 groups were displayed separately. sHG, single Heschl’s gyrus; dHG, duplicated Heschl’s gyrus. For the other pairs of functional and structural measures of the left and right PT, the gyrification pattern of HG showed no significant effect on their correlations. The scatter plots for nonsignificant correlations (PFWE > 0.05) are colored gray. NDI, neurite density index; ODI, orientation dispersion index; ns, non-significant. * denotes significant correlation in this group.

The difference in PT functional activation between subjects with single and duplicated HG.

sHG, single Heschl’s gyrus; dHG, duplicated Heschl’s gyrus; ns, non-significant. Nonsignificant differences (PFWE > 0.05) are colored gray.

The difference in PT structural measures between subjects with single and duplicated HG.

sHG, single Heschl’s gyrus; dHG, duplicated Heschl’s gyrus. Nonsignificant differences (PFWE > 0.05) are colored gray. NDI, neurite density index; ODI, orientation dispersion index; ns, non-significant.

Group-level activation of main contrasts for the HCP fMRI tasks.

Group-level hemispheric asymmetry of PT functional and structural measures

The interaction effect of “PT structural AI × HG gyrification pattern” on PT nonspeech-related functional AIs (the first specificity analysis)

The correlations of PT structural AIs with PT nonspeech-related functional activation AIs after controlling for the HG gyrification pattern (the first specificity analysis)

The interaction effect of “PT structural measure × HG gyrification pattern” on PT nonspeech-related functional activation for each hemisphere (the first specificity analysis)

The correlations of PT structural measures with PT nonspeech-related functional activation for each hemisphere after controlling for the HG gyrification pattern (the first specificity analysis)

The interaction effect of “PT structural AI × HG gyrification pattern” on speech-related functional AIs of the entire hemisphere (the second specificity analysis)

The correlations of PT structural AIs with speech-related functional AI of the entire hemisphere after controlling for the HG gyrification pattern (the second specificity analysis)

The interaction effect of “PT structural measure × HG gyrification pattern” on speech-related functional activation of the entire ipsilateral hemisphere (the second specificity analysis)

The correlations of PT structural measures with speech-related functional activation of the entire ipsilateral hemisphere after controlling for the HG gyrification pattern (the second specificity analysis)