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tutorial:shared:dataset [2014/04/30 10:50]
robert mention that data is epoched and not continuous, see http://bugzilla.fcdonders.nl/show_bug.cgi?id=2550
tutorial:shared:dataset [2017/08/17 11:21] (current)
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 MEG signals were recorded with a 151 sensor CTF Omega System (VSM MedTech Ltd.,Port Coquitlam, Canada). In addition, the EOG was recorded to later discard trials contaminated by eye movements and blinks. The ongoing MEG and EOG signals were lowpass filtered at 100 Hz, digitized at 300 Hz and stored for off-line analysis. To measure the head position with respect to the sensors, three coils were placed at anatomical landmarks of the head (nasion, left and right ear canal). While the subjects were seated under the MEG helmet, the positions of the coils were determined before and after the experiment by measuring the magnetic signals produced by currents passed through the coils. ​ MEG signals were recorded with a 151 sensor CTF Omega System (VSM MedTech Ltd.,Port Coquitlam, Canada). In addition, the EOG was recorded to later discard trials contaminated by eye movements and blinks. The ongoing MEG and EOG signals were lowpass filtered at 100 Hz, digitized at 300 Hz and stored for off-line analysis. To measure the head position with respect to the sensors, three coils were placed at anatomical landmarks of the head (nasion, left and right ear canal). While the subjects were seated under the MEG helmet, the positions of the coils were determined before and after the experiment by measuring the magnetic signals produced by currents passed through the coils. ​
  
-The MEG data are stored as epochs or trials of fixed length around each stimulus trigger, i.e. the file does not represent a continuous record of the data and the data in the inter-trial-interval is not stored. The consequence is that the data cannot be represented as a continuous record, as at the epoch boundaries there is a discontinuity. See also the [[getting_started/​ctf?&#​background|background on the CTF system]].+The MEG data are stored as epochs or trials of fixed length around each stimulus trigger, i.e. the file does not represent a continuous record of the data and the data in the inter-trial-interval is not stored. The consequence is that the data cannot be represented as a continuous record, as at the epoch boundaries there is a discontinuity. See also the [[/getting_started/​ctf?&#​background|background on the CTF system]].
  
 Magnetic resonance images (MRIs) were obtained with a 1.5 T Siemens system. During the MRI scans ear molds with small containers filled with vitamin E marked the same anatomical landmarks. This allows for realignment of the MRIs to the MEG coordinate system according to the anatomical landmarks. Magnetic resonance images (MRIs) were obtained with a 1.5 T Siemens system. During the MRI scans ear molds with small containers filled with vitamin E marked the same anatomical landmarks. This allows for realignment of the MRIs to the MEG coordinate system according to the anatomical landmarks.