High-precision neuromagnetic study of the functional organization of the human auditory cortex

Three-dimensional reconstruction of the auditory cortical areas from magnetic resonance images

The future of neuromagnetic research will be highly dependent on the development of analysis procedures utilizing morphological information derived from magnetic resonance (MR) images. However, constraining the biomagnetic inverse problem by using such information may lead to serious misinterpretations if the reconstruction algorithm for the cortical surface overlooks boundaries between grey matter and cerebrospinal fluid (CSF) or artificially generates them. The purpose of this study was to check as to what extent an advanced automatic three-dimensional reconstruction procedure is able to segment the cortical structures located hidden in the Sylvian fissure (especially Heschl's gyrus and planum temporale). The procedure consisted of four processes: a coarse segmentation, a refined segmentation of the white matter, a skeletonization of the sulci and a segmentation of the cortical surface by concurrent region growing for brain and CSF. The reconstruction result for single slices basically agrees with the impression obtained upon visual inspection of the original MR data. Photorealistic visualizations, showing a good qualitative agreement with anatomical images, suggest that the reconstructed surfaces are realistic and detailed enough to be applicable in source analyses of auditory evoked fields.