[FieldTrip] 4D-Neuroimaging Magnes 2500WH system
Sarang S. Dalal
sarang at cfin.au.dk
Wed May 4 12:50:21 CEST 2016
Does your system consist of 148 magnetometors or gradiometers? In my previous lab at the University of Konstanz, we also had the Magnes 2500WH with 148 magnetometers. In our experience, the weights were not necessary for analyses at either the sensor or source level. If your system consists of gradiometers, however, maybe these weights would be necessary?
If you really need those weights, I believe you can find them in the header structure, somewhere in data.hdr.orig. You will then need some knowledge on how to apply those weights.
From: fieldtrip-bounces at science.ru.nl <fieldtrip-bounces at science.ru.nl> on behalf of Ling Wang <lingwang at m.scnu.edu.cn>
Sent: Wednesday, May 4, 2016 11:32 AM
Subject: [FieldTrip] 4D-Neuroimaging Magnes 2500WH system
We recently started a joint study with the staff of a hospital specialized for brain diseases, where there is a 4D-Neuroimaging Magnes 2500WH system. We have collected a sample MEG data with the system to see if we can perform experiments with the system. I am trying to analyze the data with FieldTrip. As introduced in the tutorial (http://www.fieldtriptoolbox.org/getting_started/bti), the software currently reads digital balancing weights only for the Magnes 3600 system but not the 148-channel system. And yes, the software does not compute the balancing matrix for our MEG data, as indicated by the function, ft_read_header, "not applying digital weights in the gradiometer balancing matrix", when reading our MEG data.
I have three questions about analyzing these Magnes 2500WH MEG data with FieldTrip.
1) Can we still carry out the analyses (ERF, TRF and connectivity) correctly at the sensory-level?
2) Is there a plan that FieldTrip would read the digital balancing weights for the MEG data of the Magnes 2500WH system?
3) If we want to program to read the weights, what information do we need and possibly where can find the related information (e.g., the user manual of the system?)?
Thanks in advance.
School of Psychology
South China Normal University
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