MEG median nerve dataset - CTF
File: sample_raw.zip
License
This tutorial dataset (MEG and MRI data) remains a property of the MEG Lab, McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Canada. Its use and transfer outside the Brainstorm tutorial, e.g. for research purposes, is prohibited without written consent from the MEG Lab.
If you reference this dataset in your publications, please acknowledge its authors (Elizabeth Bock, Esther Florin, Francois Tadel and Sylvain Baillet) and cite Brainstorm as indicated on the website. For questions, please contact us through the forum.
Presentation of the experiment
Experiment
- One subject, one acquisition run of 6 minutes
- Subject stimulated using Digitimer Constant Current Stimulator (model DS7A)
- The run contains 200 electric stimulations randomly distributed between left and right:
- 102 stimulations of the left hand
- 98 stimulations of the right hand
- Inter-stimulus interval: jittered between [1500, 2000]ms
Stimuli generated using PsychToolBox on Windows PC (TTL pulse generated with the parallel port connected to the Digitimer via the rear panel BNC)
MEG acquisition
Acquisition at 1200Hz, with a CTF 275 system, subject in seating position
- Recorded at the Montreal Neurological Institute in November 2011
- Anti-aliasing low-pass filter at 300Hz, files saved with the 3rd order gradient
- Recorded channels (302):
- 1 Stim channel indicating the presentation times of the stimuli: UPPT001 (#1)
- 26 MEG reference sensors (#3-#28)
- 272 MEG axial gradiometers (#29-#300)
- 1 ECG bipolar (#301)
- 1 vertical EOG bipolar (#302)
- 1 Unused channels (#2)
1 dataset: subj001_somatosensory_20111109_01_AUX-f.ds
Stimulation delays
Delay #1: 4 samples @ 1200Hz = 3.3ms. The CTF MEG system has an anti-aliasing filter (1/4 the sampling rate) applied at the time of recording. This filter is applied only to the MEG channels and not to the stimulus channels. Therefore the MEG has a 4 sample delay when compared with the stimulus channel.
Head shape and fiducial points
3D digitization using a Polhemus Fastrak device (subj00111092011.pos)
Position of the anatomical references used for these recordings:
The position of the CTF head localization coils, pictures available in file fiducials.jpg- Around 110 head points distributed on the hard parts of the head (no soft tissues)
Subject anatomy
- Subject with 1.5T MRI
Processed with FreeSurfer 5.2