[FieldTrip] Neuromag306 Gradiometer Channels Have two types of directions, how to do interpolation

[Schoffelen, J.M. (Jan Mathijs)]

Hi Yiheng,

I would strongly recommend against using ft_channelrepair for MEG data. I cannot think of a good reason to do this.

Best wishes,
Jan-Mathijs


On 15 Jul 2024, at 14:17, 胡益衡 via fieldtrip <fieldtrip at science.ru.nl> wrote:


Hi everyone,


 I want to use ft_channelrepair to interpolate some bad gradiometer channels. However, I found that there are two types of gradiometer channels whose directions are orthogonal (see https://imaging.mrc-cbu.cam.ac.uk/meg/VectorviewDescription). I want to know whether it is necessary to divide the grad neighbour structure in 'neuromag306planar_neighb.mat' into two parts, latitude and longitude, to do interpolation? Because I am afraid that mixed different directions signals in gradiometer channels will influence source reconstruction. Or maybe the two types of gradiometer just emphasize the orthogonal relationship. When doing interpolation, I only need to remove the channel whose distance to their neineighbors is 0 according to the grad.chanpos.


 Also, I want to know how the neighbor structure in 'neuromag306planar_neighb.mat' is defined. In the grad.chanpos, planar gradiometer channels along longitude and latitude have the same position array as magnetometer channel, but some channels in structure only contain one gradiometer channel, e.g. in 'neuromag306planar_neighb.mat', MEG0113 has neighbors MEG0112, MEG0122, MEG0132, MEG0133, MEG0142, MEG0123 but not includes MEG0143. MEG0143 has the same grad.chanpos as MEG0142. Is it defined by calculating the distance with coil position (grad.coilpos)?


Best,

Yiheng

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