Reconstruction of quasi-radial dipolar activity using three-component magnetic field measurements

ObjectiveWhile standard magnetoencephalographic systems record only one component of the biomagnetic field, novel vector-biomagnetometers enable measurement of all three components of the field at each sensing point. Because information content in standard one-component magnetoencephalography (MEG) is often not adequate to reconstruct quasi-radial dipolar activity, we tested the hypothesis that quasi-radial activity can be estimated using three-component MEG.MethodsWe stimulated the right median nerve in 11 healthy volunteers and recorded the somatosensory evoked fields over the contralateral hemisphere using a novel vector-biomagnetometer system comprised of SQUID-based magnetometer triplets. Source reconstruction for the early cortical components N20m and P25m was subsequently performed.ResultsBoth tangential and quasi-radial dipolar activity could be reconstructed in 10 of the 11 participants. Dipole locations were found in the vicinity of the central sulcus, and dipole orientations were predominantly tangential for N20m and quasi-radial for P25m. The mean location difference between the tangential and quasi-radial dipoles was 11.9 mm and the mean orientation difference was 97.5°.ConclusionsQuasi-radial dipolar activity can be reconstructed from three-component magnetoencephalographic measurements.SignificanceThree-component MEG provides higher information content than does standard MEG.

► Novel vector-biomagnetometers enable reconstruction of quasi-radial brain activity. ► We demonstrate this reconstruction of radial brain activity for Brodmann area 1 in the somatosensory system. ► Vector-biomagnetometers provide greater insight into brain activity than does standard magnetoencephalography.