Figure 2.

Intra‐ and interhemispheric white matter connections between language areas. Superior view of a T1‐weighted axial MRI slice. The red surfaces mark the cortical gray matter adjacent to the 4 ROIs located in the left and right pSTG and oIFG. These ROIs, of identical white matter volume, have been generated by a geodesic region‐growing algorithm so that they follow the brain conformation. They are initialized at the local maximum of the fMRI activations related to language comprehension or production (see Patients and Methods). Yellow‐red denotes intrahemispheric connections; magenta‐blue denotes interhemispheric. The latter crossed in the body of the corpus callosum when linking both oIFG, or in the isthmus for the pSTG. A: RH men typically presented a marked asymmetry in the pSTG–oIFG bundle, with more fibers in the left hemisphere. Posterior interhemispheric connections were numerous. B: LH men typically presented little asymmetry in the pSTG–oIFG bundle. The posterior interhemispheric connections were sparse. RH (C) and LH (D) women had similar connectivity patterns; i.e., both had a strong intra‐ and interhemispheric connectivity.