Detecting and correcting for head movements in neuromagnetic measurements

Head movements during neuromagnetic measurements may cause a significant er ror in the estimated locations of active brain areas. In this study we pres ent a fast method for measuring the head position while neuromagnetic data are acquired. We then compare two methods for removing the effect of the mo vements in neuromagnetic source estimation and magnetic field alignment: mi nimum-norm estimate alignment and forward calculation correction. Simulatio ns and a test measurement show that the proposed head position measurement method works with millimeter precision and that incorporating the effect of the head movements into the magnetic field forward calculations is an effi cient and a sufficiently accurate method for correcting for the head moveme nts. (C) 2001 Academic Press.