Dear Chris,
You should re-save the template locations without prefixes as I
explained before and then use 'Prepare' (spm_eeg_prep) to load this
file before doing coregistration. I'd suggest you to use the GUI at
the first instance. Once you figure out what to do, this can be
batched, see (http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;f828c05c.1110).
Best,
Vladimir
On Wed, Oct 26, 2011 at 1:02 PM, Christopher Brown
<[log in to unmask]> wrote:
> Dear Vladimir,
>
> Thanks for your input on this. I'm struggling to get SPM to provide options for inputting electrode positions and fiducial positions, or selecting the headshape option. At present the spm_eeg_inv_datareg_ui automatically performs the coregistration (presumably using the template you mentioned?) without providing any options for other input. Is there a way to get it to come up with those options? I'm using it from the command line.
>
> Many thanks,
> Chris
>
> ________________________________________
> From: Vladimir Litvak [[log in to unmask]]
> Sent: 25 October 2011 19:32
> To: Christopher Brown
> Cc: [log in to unmask]
> Subject: Re: [SPM] EEG electrode coregistration
>
> Dear Chris,
>
> The template locations are stored already in MNI space under
> spm/MEEGtemplates/ext1020.sfp . You could save ext1020.sfp under a
> different name, remove 'spm' prefixes from the fiducial names and then
> find at least 3 electrodes whose positions for your lab you can find
> on the MNI template image. You can then load the file as individual
> electrode locations and use those electrodes as fiducials with the
> 'type' option to enter the corresponding MNI coordinates. You might
> want to say 'no' to 'use headshape' and see if that works better.
>
> Alternatively, if you have a 3D digitizer you could digitize one
> subject with the cap put the way you put it + fiducials and use that
> as individual electrode positions for all subjects. EEGLAB and
> Fieldtrip have some tools for manual alignment that you might want to
> look at.
>
> Best,
>
> Vladimir
> On Tue, Oct 25, 2011 at 5:57 PM, Chris Brown
> <[log in to unmask]> wrote:
>> Dear SPMers,
>>
>> I am performing EEG source localisation using the batch tool. We did not measure electrode positions or MRIs so I'm relying on the defaults (61 scalp electrodes, extended 10-20 system). However, the main source I have estimated for a well-known ERP (the P2 peak of the laser-evoked potential) is too deep in the brain by at least 2-4cm, appearing in the corpus callosum when it should be in the mid/posterior cingulate. My guess is that there is an issue with the electrode positions, because the way we position our caps appears different to how the electrodes are positioned in MNI space according to the images created by SPM. SPM appears to automatically create coordinates in MNI space. Is there a way to manually adjust the way this step is performed?
>>
>> Many thanks,
>> Chris
>>
>
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