[FieldTrip] no coil pos for planar combined data

Eelke Spaak eelke.spaak at donders.ru.nl
Tue Oct 21 17:05:07 CEST 2014


Hi Kaelasha,

Why do you want to do source analysis on combined planar gradiometer
data? In general, I would say this does not make sense. Instead, I
would use the original (axial or planar, depending on your system)
gradiometer data.

Best,
Eelke

On 21 October 2014 15:57, Kaelasha Tyler <ktyler at swin.edu.au> wrote:
> Hi all,
>
> I am having problems using ft_sourceanalysis with planar gradiometer data.
>
> I am following a tutorial for beamforming with lcmv method (which I believe is a work in progress) found here:
> http://fieldtrip.fcdonders.nl/tutorial/beamformer_lcmv?s[]=covariancewindow
> Using planar gradiometer data is mentioned in the tutorial, although not in detail.
>
> My problem:
> The .avg field produced by time locking, is lost when combining planar gradiometers using 'ft_combineplanar'.
> In this case, I am unable to to use 'ft_sourceanalysis' on combined planar gradiometer data.
> I get the error: Reference to non-existent field 'avg'.
>
> I reasoned that I may be able to keep the .avg filed if I combine the planar gradiometer data at the outset, prior to timelocking. But in this case, the gradiometer positions in data.grad does not include 'coilpos'. Eg, no data.grad.coilpos.
> When calling 'ft_sourceanalysis' in this case, I get the error: Reference to non-existent field 'coilpos'.
>
> Any suggestions?
>
> If the .grad.coilpos was retained when I combined the planar gradiometer data at the outset, (after preprocessesing and prior to timelokcing) then I would be able to use ft_sourceanalysis on planar gradiometer combined data successfully.
> Is that possible?
>
> Thanks in advance! (and thank you to all previous very helpful responses on this list).
>
> Kaelasha Tyler
>
> PhD Candidate
> Brain and Psychological Science Research Centre
> Swinburne University of Technology
> Melbourne
> Australia
>
>
>
>
>
>



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