Visualization of Tonotopy of Auditory Cortex Using a Newly Developed 129 Channel Vector Magnetoencephalography

The existence of the human tonotopic organization has been revealed using the neuromagnetic measurement. These early studies on the tonotopic organization in the human were performed by measuring sequentially at many sites using the magnetoencephalography (MEG) with a few channels 1, 2, 3, so these studies needed a vast effort and time to fulfill a study. This meant that we could not use mangentoencephalography (MEG) to investigate the auditory function of patients in clinical setting. Now, many MEG systems, which are commercially available, consist of multi-channel first-order axial gradometers or planar gradiometers. These have some advantages; specially, axial gradiometer is sensitive to the radial component of magnetic fields, and planar gradiometer is favorable to obtain their tangential component. Even using these two systems, however, we could not obtain three dimensional components about magnetic fields. Consequently, we have developed a new 129 channel vector magnetometer system5).