Postcentral origin of P22: evidence from source reconstruction in a realistically shaped head model and from a...

The source of the radial field of P22 was previously attributed either to the precentral (area 4) or postcentral (area 1) gyrus, on the basis of interpretation of potential maps recorded on the skin or cortex, respectively. The present study used dipole localization within realistically shaped head models and constrained the inverse solution by using the individual cortex and the normals on it, as derived from MR-tomography. In all normal subjects in which a sufficient solution was obtained (6 of 10, goodness of fit above 90%, and relative power of above 94.4% in principal-component analysis) the P22 source resided at the crown of the postcentral gyrus. Further evidence came from a patient with a postcentral lesion (area 1) and loss of P22, while N20-P20 was preserved.