Quantitative analysis of MEG using modified sLORETA for clinical application.
OBJECTIVE
To determine whether standardised low-resolution brain electromagnetic tomography modified for a quantifiable method (sLORETA-qm) can be used for quantitative analysis in magnetoencephalography (MEG).


METHODS
Somatosensory 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 x threshold of thenar muscle twitch (TMT). N20 m intensity changes were analysed quantitatively using sLORETA-qm. Then, SEFs were measured with stimulation on the median nerve at 1.5 x TMT from 47 hemispheres in 24 subjects. sLORETA-qm intensity and the equivalent current dipole (ECD) moment of N20 m were calculated, and relationships between the values were evaluated.


RESULTS
sLORETA-qm intensity increased linearly with stimulus intensity between 0.75 and 1.5 x 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 (r(s)=0.91, p<0.001).


CONCLUSIONS
The results of this study focusing on N20 m suggested that sLORETA-qm is reliable for quantitative analysis of MEG as well as ECD models.


CONCLUSIONS
sLORETA-qm appears promising for quantitative analyses of MEG for which ECD models are inappropriate.
Department of Neurosurgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, 545-8585 Osaka, Japan. Electronic address: terakawa@msic.med.osaka-cu.ac.jp.
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Y
Terakawa
Department of Neurosurgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, 545-8585 Osaka, Japan.
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Tsuyuguchi
MEG Center, Yokogawa Electric Corporation, Kanazawa, Japan.
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Tanaka
Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan.
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Y
Shigihara
Department of Radiology, Osaka City University Graduate School of Medicine, Osaka, Japan.
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Sakamoto
Department of Neurosurgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, 545-8585 Osaka, Japan.
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Takami
Department of Neurosurgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, 545-8585 Osaka, Japan.
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Ohata
D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D007839:Functional Laterality; D006801:Humans; D016014:Linear Models; D015225:Magnetoencephalography / Q000379:methods* / Q000592:standards*; D008297:Male; D008475:Median Nerve / Q000502:physiology / Q000528:radiation effects