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Grand Average in MEG and Crude Estimation of Anatomical Site  

Kwon H. (Biomagnetism Research Center, Korea Research Institute of Standards and Science)
Kim K. (Biomagnetism Research Center, Korea Research Institute of Standards and Science)
Kim J. M. (Biomagnetism Research Center, Korea Research Institute of Standards and Science)
Lee Y. H. (Biomagnetism Research Center, Korea Research Institute of Standards and Science)
Park Y. K. (Biomagnetism Research Center, Korea Research Institute of Standards and Science)
Publication Information
Journal of Biomedical Engineering Research / v.25, no.6, 2004 , pp. 575-580 More about this Journal
Abstract
In this work, a method is presented to find an anatomical site of a current source crudely in a standard brain using grand average of MEG data. Minimum norm estimation algorithm and truncated singular value decomposition were applied to calculate the distributed sources that can reproduce the measured signals. Grand average over all subjects was obtained from the transformed signals, which would be detected in a standard sensor plane by the obtained distributed current sources. In the simulation study, it was shown that the localized dipole using the grand average is consistent with the mean location of localized dipoles of all subjects within several mm even with large inter-individual differences of sensor positions. This result suggests that the mean location of low level signal source can be estimated as a dipole source in grand average and it was confirmed in the localization of the current source of N100m. when the localized dipole is registered on a standard brain. This result also suggests that the activity region obtained from grand average can be crudely estimated on a standard brain using the source location of the N100m as a reference point.
Keywords
Magnetoencephalography; Minimum norm estimation; Grand average; Standard brain; Auditory cortex; Anatomical site;
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