Different distribution patterns of individual hand somatosensory representations in different coordinate systems

.We analyzed and compared the distribution patterns of somatosensory evoked field (SEF) sources expressed in the head-based coordinate and spatially normalized AC–PC coordinate spaces. Significant gender differences in SEF source locations were found in the head-based coordinates, which then disappeared after spatial normalizations. In contrast, significant hemispheric asymmetries in the SEF source locations were found irrespective of the coordinate spaces. Hemispheric asymmetry in the courses of individually traced central sulci still remained after normalizations. These results show that the distribution patterns of SEF sources can be greatly affected by the choice of coordinate spaces. In the head-based coordinate system, individual variations in head/brain size were most influential in biasing gender comparisons. Spatial normalization methods significantly reduced these biases, however, considerable anatomical variations remained.