Differential language expertise related to white matter architecture in regions subserving sensory-motor coupling, articulation, and interhemispheric transfer

Abstract

The technique of diffusion tensor imaging (DTI) has been used to investigate alterations in white matter architecture following long-term training and expertise. Professional simultaneous interpreters (SI) provide an ideal model for the investigation of training-induced plasticity due to the high demands placed on sound to motor mapping mechanisms, which are vital for executing fast interpretations. In line with our hypothesis, we found clusters with decreased fractional anisotropy (FA) in the SI group in brain regions previously shown to support sensory-motor coupling mechanisms and speech articulation (cluster extent family-wise error corrected, P < 0.01). Furthermore, we found an altered white matter architecture indicated by lower FA values in the SI group in the most anterior and posterior parts of the corpus callosum. Our results suggest that language expertise is accompanied by plastic adaptations in regions strongly involved in motor aspects of speech and in interhemispheric information transfer. These results have implications for our understanding of language expertise in relation to white matter adaptations.

Figure 1

FA, controls versus SI. Statistical parametric maps of the voxel‐based fractional anisotropy analysis overlaid on the MNI‐152 template and thresholded with P < 0.01, FWE‐corrected at the cluster extent level. Shown are regions with increased fractional anisotropy in the control subjects compared with simultaneous interpreters in the left insula (A, left image), in the genu (B, left and right image), and in the body and splenium (C) of the corpus callosum (right image).The color bar represents the t‐values.

Figure 2

Average mean diffusivity (mm²/s). The figure depicts average axial and radial diffusivity for each significant cluster and group.