A Multivariate Analysis of Evoked Responses in EEG and MEG Data |
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| Authors: | K. J. Friston K. M. Stephan J. D. Heather C. D. Frith A. A. Ioannides L. C. Liu M. D. Rugg J. Vieth H. Keber K. Hunter R. S. J. Frackowiak |
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| Affiliation: | aThe Wellcome Department of Cognitive Neurology, National Hospital, Queen Square, London, WC1N 3BG, United Kingdom;bDepartment of Neurology, University of Dusseldorf, Dusseldorf, 40225, Germany;cDepartment of Physics, The Open University, Milton Keynes, MK7 6AA, United Kingdom;dWellcome Brain Research Group, School of Psychology, University of St Andrew's, St. Andrew's, KY16 9JU, United Kingdom;eDepartment Experimental Neuropsychiatry, University of Erlangen, Nuremberg, Germany |
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| Abstract: | This paper presents a multivariate analysis of evoked responses and their spatiotemporal dynamics as measured with electro- or magnetoencephalography. This analysis uses standard techniques (ManCova) to make possible statistical inference about differential responses, after the data have been transformed using singular value decomposition. The generality of this approach is limited only by the assumptions implicit in the general linear model and can range from simple analyses like Hotelling'sT2test (in comparing evoked responses among different conditions) to complex analyses of a multivariate regression type (e.g., characterizing the response components associated with a behavioral or psychophysical parameter). To illustrate the technique we have characterized time-dependent changes (both within and between trials) in magnetic fields, evoked by self-paced movements. Our illustrative analysis showed that movement-evoked components were less prone to adaptation than premovement components, suggesting that functionally distinct (preparatory and early executive) biomagnetic signals show differential adaptation. |
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