Partial signal space projection for artefact removal in MEG measurements: a theoretical analysis.

Standard methods for artefact removal in MEG or EEG measurements consist of rejection of either corrupted epochs or signal space projection (SSP). We propose to combine the two methods by applying SSP only in corrupted epochs and thus using both temporal and spatial information. This partial signal space projection necessarily results in smaller variances for the source localization. Formulae for dipole localization errors as a function of fraction of corrupted epochs are derived and verified in Monte Carlo simulations of MEG measurements corrupted with eye artefacts. A theoretical analysis of various measuring devices, classes of artefact and locations of dipole of interest shows that the proposed method leads to significant improvement for frontal signal dipoles and for 30-80% corrupted epochs.

[1]  G. Curio,et al.  The effect of artifact rejection by signal-space projection on source localization accuracy in MEG measurements , 1999, IEEE Transactions on Biomedical Engineering.

[2]  P Berg,et al.  A multiple source approach to the correction of eye artifacts. , 1994, Electroencephalography and clinical neurophysiology.

[3]  V. Jousmäki,et al.  Cardiac artifacts in magnetoencephalogram. , 1996, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[4]  A Bezerianos,et al.  Data dependent weighted averages for recording of evoked potential signals. , 1995, Electroencephalography and clinical neurophysiology.

[5]  B. Lutkenhoner.  Current dipole localization with an ideal magnetometer system , 1996, IEEE Transactions on Biomedical Engineering.

[6]  Cees J. Stok,et al.  The influence of model parameters on EEG/MEG single dipole source estimation , 1987, IEEE Transactions on Biomedical Engineering.

[7]  G Curio,et al.  On the calculation of magnetic fields based on multipole modeling of focal biological current sources. , 1997, Biophysical journal.

[8]  B. Rockstroh,et al.  Removal of ocular artifacts from the EEG--a biophysical approach to the EOG. , 1985, Electroencephalography and clinical neurophysiology.

[9]  J. Sarvas.  Basic mathematical and electromagnetic concepts of the biomagnetic inverse problem. , 1987, Physics in medicine and biology.