SpmAnalysis - Meg Wiki

Revision 54 as of 2009-01-27 12:06:59

Clear message
location: SpmAnalysis

Analysis of MEG Data in SPM5

Many of us here use SPM for EEG and/or MEG analysis. The main reason is that SPM is freeware (requiring only Matlab), and thus modifiable and relatively easily to understand (if you have basic knowledge of a procedural computer language, given that Matlab is a fairly high-level language). Several of us are actively extending SPM for our own purposes, particularly in relation to the Neuromag type of MEG data.

SPM also offers some unique features, not available in other packages:

The code

SPM has been developed at the FIL (in London), with input from people round the world. Here is its home: http://www.fil.ion.ucl.ac.uk/spm/

At the moment, we are using "SPM5" (with any latest updates automatically pulled from the FIL). At the CBU, SPM5 is installed here:

/imaging/local/spm/spm5

We have edited/refined some of these functions. These modifications are stored here:

/imaging/local/spm/spm5/cbu_updates

If you start SPM5 from Linux using Rhodri's wrappers, both these directories will be added to your Matlab path, with the cbu_updates directory higher in the path (so you will be using local CBU versions of any functions duplicated across these directories).

The functions in cbu_updates may be periodically updated, which will be preceded by an email to CBU imagers. More recent changes are under subversion control (SVN): If you are an external collaborator (outside the CBU network), or want access to the most recent changes (at your own risk), consult MeegCodeCbuSvn.

In the future, we will move to "SPM8". One exciting reason for this is that SPM8 will share the same data format with Field-Trip and EEGLAB (which are also Matlab packages for analysing EEG+MEG data). This will allow us to take the best features of each (e.g, source localisation and dynamic causal modelling in SPM8; time-frequency analysis and beam-formers in Field-Trip; Independent Component Analysis in EEGLAB). This is another advantage of Matlab-based academic-community-based freeware.

Basic preprocessing and source localisation in SPM8 will not differ much from SPM5. Tne main improvements concern Dynamic Causal Modelling (DCM) for EEG/MEG (together with better graphics and GUI). The reason that we are sticking with SPM5 for the moment is that the data format and forward modelling for Neuromag data is not quite finalised in Field-Trip/SPM8.

Demos

  • For specific demo using data from our Neuromag MEG machine, see SpmDemo

  • For a fuller demo of other EEG/MEG analysis in SPM5 (though from a different MEG machine), including more general features (e.g, time-freq analysis, 3D statistical maps), with proper step-by-step instructions via the GUI, see: http://www.fil.ion.ucl.ac.uk/spm/data/mmfaces.html

  • For a more theoretical introduction to source localisation in SPM5, see these slides: attachment:henson-SPM-Grad08-4-meeg.ppt

Some relevant papers

  • Summary of localisation approach using ReML for evoked and induced responses (mathematical; cites earlier development papers too): attachment:FristonEtAl_hbm_06.pdf

  • Basic considerations for Group Analyses (though using individual meshes): attachment:HensonEtAl_NI_07.pdf

  • Use of inverse-normalised ("canonical") cortical meshes: attachment:MattoutEtAl_JCIN_07.pdf

  • Choice of forward models for MEG (e.g, single-sphere vs BEM), including further validation of canonical meshes: attachment:HensonEtAl_NI_inpress.pdf

  • New method of Multiple Sparse Priors (MSP): attachment:FristonEtAl_NI_08_MSP.pdf