[FieldTrip] combining gradiometer/magnetometer sensors - neuromag data

Klink-3, N.E.C. van N.vanKlink-2 at umcutrecht.nl
Wed May 10 09:33:22 CEST 2017

Hi Andria,

We have been struggling with the same problem, also using a 306-channel Neuromag system. We ended up correcting for the scale difference between magnetometer and gradiometer signals (i.e. noise 5e-15T vs 5e-13T/m). So we multiplied the signals of the magnetometers and the leadfield values of the magnetometers by a factor 100. This gave us the best result.

Kind regards,

Van: fieldtrip-bounces at science.ru.nl [mailto:fieldtrip-bounces at science.ru.nl] Namens Andria Pelentritou
Verzonden: 10 mei 17 1:52
Aan: fieldtrip at science.ru.nl
Onderwerp: [FieldTrip] combining gradiometer/magnetometer sensors - neuromag data

Greetings from Melbourne!

We've been using fieldtrip (v-20160801) for a while now and we are having issues when it comes to combining magnetometer and gradiometer MEG sensors types during (LCMV) beamforming for the Elekta Neuromag Triux 306-channel system. Beamforming the magnetometers or gradiometers separately on auditory evoked data works well, but we cannot successfully combine the two sensor types. We've played with the cfg.coilaccuracy variable as advised in one of the tutorials with no luck as there seem to be no obvious effects on the output. The documentation provides very little information on the topic.

What strategies would you recommend when trying to combine the Neuromag 306-channel system magnetometer/gradiometer data?

Many thanks in advance for your help and many more thanks for releasing such a valuable toolbox!
Warm regards


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