Quantitative analysis of MEG using modified sLORETA for clinical application

ObjectiveTo determine whether standardised low-resolution brain electromagnetic tomography modified for a quantifiable method (sLORETA-qm) can be used for quantitative analysis in magnetoencephalography (MEG).MethodsSomatosensory evoked fields (SEFs) were obtained from 10 hemispheres of five healthy volunteers stimulated on the median nerve at 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 × threshold of thenar muscle twitch (TMT). N20m intensity changes were analysed quantitatively using sLORETA-qm. Then, SEFs were measured with stimulation on the median nerve at 1.5 × TMT from 47 hemispheres in 24 subjects. sLORETA-qm intensity and the equivalent current dipole (ECD) moment of N20m were calculated, and relationships between the values were evaluated.ResultssLORETA-qm intensity increased linearly with stimulus intensity between 0.75 and 1.5 × TMT, and tended to reach a plateau or decrease at higher stimulus intensities. The distribution of sLORETA-qm intensity after natural logarithmic transformation was normal and a close correlation was found between the ECD moment and sLORETA-qm intensity (rs = 0.91, p < 0.001).ConclusionsThe results of this study focusing on N20m suggested that sLORETA-qm is reliable for quantitative analysis of MEG as well as ECD models.SignificancesLORETA-qm appears promising for quantitative analyses of MEG for which ECD models are inappropriate.