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I can confirm that I also sometimes get 0 spatial modes left when using group inversion for MSP, whether Mags only, Grads only or both (ie it appears to be the group inversion that is problematic). The same data gives reasonable inversions when I use MSP without group inversion (ie individual MSP), or MNM or COH. So it must be a problem with the realignment of leadfields; not the leadfields themselves (and I get the same problem whether I use single-shell or single-sphere forward models). Unfortunately I haven't yet tracked down why this happens, because on other Neuromag datasets in the past, the group inversion worked fine. I have confirmed that the spm_eeg_invert function (in which the leadfield realignment is done) has not changed during that time, so I can only assume that something else "deep down" in the forward modelling (eg FieldTrip) functions has changed since then? Note that I don't think it can be anything to do with the way the data is preprocessed (eg via SSS or SSP), because the MEG data are not used when realigning the leadfields. (Though note that, even if group inversion did work, any spatial adjustment done to the data, eg via SSS or SSP, should, in principle, also be applied to the forward modelling. I'm not sure what is done with any SSP vectors when SSS is applied, but assume that any such SSP vectors present are applied when the data are converted (via the FieldTrip-MNE FIF-reading functions) - and would hope they are also therefore stored somewhere so FieldTrip can adjust leadfields accordinly, but I think we would need advice from a FieldTrip expert....?) Sorry not to be more help - I am still puzzling! BW,R ------------------------------------------------------- DR RICHARD HENSON Assistant Director for Neuroimaging MRC Cognition & Brain Sciences Unit 15 Chaucer Road Cambridge, CB2 7EF England EMAIL: [log in to unmask]<mailto:[log in to unmask]> URL: http://www.mrc-cbu.cam.ac.uk/people/rik.henson/personal TEL +44 (0)1223 355 294 x501 FAX +44 (0)1223 359 062 MOB +44 (0)794 1377 345 ------------------------------------------------------- ________________________________ From: SPM (Statistical Parametric Mapping) [[log in to unmask]] on behalf of [log in to unmask] [[log in to unmask]] Sent: 02 May 2012 19:49 To: [log in to unmask] Subject: [SPM] MEG group comparison neuromag Dear SPM users, I tried to do a group inversion with neuromag MEG data (2 conditions, 18 subjects). When I include MEGPLANAR I get 0 spatial modes and NaNs. For the MEG I get 1 spatial mode (if I invert individually I get 66 modes for MEG and 104 modes for MEGPLANAR). So, if I only use MEG to get a solution, I get for all subjects, conditions the same solutions (and a very unlikely one, beam former, MNE and LORETA get visual cortex activity, GS group inversion gets auditory activity that is equal for all conditions and subjects). I saw similar postings in the SPM list in 2010 and it was advised to wait for a newer SPM version. I have used the newest 2012 SPM version. I did tSSS with the MEG data, but I do not know if SPM applies the SSP vectors to the data (it shouldn't when using tSSS). Could this be the problem? Best, Stephan ________________________________________________________ Stephan Moratti, PhD see also: http://web.me.com/smoratti/ Universidad Complutense de Madrid Facultad de Psicología Departamento de Psicología Básica I Campus de Somosaguas 28223 Pozuelo de Alarcón (Madrid) Spain and Center for Biomedical Technology Laboratory for Cognitive and Computational Neuroscience Parque Científico y Tecnológico de la Universidad Politecnica de Madrid Campus Montegancedo 28223 Pozuelo de Alarcón (Madrid) Spain email: [log in to unmask]<mailto:[log in to unmask]> Tel.: +34 679219982 El 02/05/2012, a las 20:03, Liam Mason escribió: Hi Carlos, Did you get any answer of if it is possible to extract %SC from a group of subjects? I'm afraid the only way I know is to do them iteratively as you say. If marsbar is able to do it from a second-level (group) SPM file, then would be keen to know! Liam --- School of Psychological Sciences University of Manchester 0161 275 2692 ________________________________________ From: SPM (Statistical Parametric Mapping) [[log in to unmask]<mailto:[log in to unmask]>] on behalf of Ming-Tsung Tseng [[log in to unmask]<mailto:[log in to unmask]>] Sent: 24 April 2012 18:14 To: [log in to unmask]<mailto:[log in to unmask]> Subject: Re: [SPM] Compare 2 methods to extract %signal change in MarsBaR Hi Matthew, Excellent to get your clear explanation!! So I can use Method 2 to extract Beta values in a group of subjects, right?? One more question: Since %SC and Beta value can both represent neural response in an ROI, which one is better?......I mean, if I want to extract %SC, I have to use Method 1 which will be performed subject by subject and time-consuming (or any time-saving way to get %SC within many ROIs in a group of subjects)? Thanks indeed! Carlos