[FieldTrip] Neighbors for Elekta Neuromag 306 gradiometers separately?

[Lin Wang]

Dear all,

I have the same question. Do we need to separate the two gradiometer
sensors at one position when defining the neighbours for interpolating bad
sensors?

Thanks!

Lin

On Thu, Sep 17, 2015 at 3:43 AM, Darinka Trübutschek <darinkat87 at gmail.com>
wrote:

> Dear Fieldtrip community,
>
> I am new to MEG/fieldtrip and have a question regarding the neighbor
> structure necessary for computing cluster-based statistics. I am currently
> analyzing data from a Neuromag 306 system (with 102 Mags and 204 Grads) and
> would like to look separately at Mags, Grad1, and Grad2.
> I assume that this means that I also need to compute the neighbors
> separately for the different channel types.
>
> My question therefore concerns fieldtrip's standard neighbor templates for
> Neuromag. Is there a specific reason (theoretical or methodological), why
> there are no separate templates for Grad1 and 2? All that I could find are
> separate templates for Mag (neuromag306mag_neighb.mat), the combined planar
> gradients (neuromag306cmb_neighb.mat), and the neuromag306planar_neighb.mat
> template, which, if I understand correctly, does not combine the Grads, but
> still lists sensors of one type as neighbors of sensors of another type
> (e.g., for sensor 0713 - a gradiometer measuring the derivative along the
> longitudinal component, the neighbors listed include 0432, 0723, but also
> sensors that, if I interpret it correctly, should measure the derivative
> along the latitudinal component, such as 0433, 0712, etc.) Is there a
> specific reason, why sometimes, for a given sensor position, both Grad1 and
> Grad2 are included in the neighbors (e.g., 0432 and 0433), but sometimes
> only one of the two (e.g., 0742)?
>
> Many thanks in advance for your help!
>
> Best,
> Darinka
> --
> Darinka Trübutschek (PhD Candidate)
>
> Inserm-CEA Cognitive Neuroimaging Unit
> CEA/SAC/DSV/DRM/Neurospin
> Bât 145, Point Courier 156
> F-91191 Gif-sur-Yvette
>
> website: https://sites.google.com/site/dtruebutschek/
>
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