When you are ready with your experiment and would like to test it on the MEG machine before running subjects, contact Rob Rohloff to set aside a time during the week when you can test your triggers on the Machine. See Getting Started for information on how to access the current MEG scanner schedule at Froedtert Hospital.
Preparing an experiment
Come down to the MEG lab when there is some free time in the schedule and ask the lab technician to be present so there is help. Please make sure that you speak with Rob and notify him that you will be in the MEG suite during that time. Click on the 'change Project' tab and select 'new'. Fill in the basic info there and save under the project name you've selected.
- Although some people use their PI as a project name, this is a bit risky since recording parameters could change across studies. It could be better to create a study-specific project every time you start a new study.
- But NOTE that a single 'Project' can be associated with a bunch of different 'Settings'. So to be safe you should make sure to explicitly load your 'Settings' every time, after you load the Project.
Now save this and click the button to change the acquisition settings. Several options here:
- You need to make sure you've selected all the MEG channels and possibly a subset of EEG channels. Confusingly, 61-64 are reserved for the bipolar channels, even if your cap has more than 60 channels...they pick up again at 65. So if you plan to record HEOG, VEOG, and/or ECG (heartbeat), make sure these are selected.
So after you have selected 61, 62, and 64, right click on each sequentially and choose either 'EOG' or 'ECG' as appropriate. If you leave them coded as EEG type instead of EOG type, the EEG digitization will be incorrectly mapped and it will be a big pain to reconstruct post-processing.
- Decide on online high-pass and low-pass filters. Convention in EEG literature is highpass of .01 Hz. Low-pass cutoff usually doesn't matter as long as it's >= 100 Hz.
- Decide on a sampling rate. The maximum allowed sampling rate depends on the data acquisition hardware and the slider automatically reflects the limitation imposed by the hardware. (Make sure it is atleast twice your low pass frequency according to the Nyquist Criterion)
Sometimes the Acquisition computer freezes, this can most often be fixed by rebooting the Acquisition machine. Go to Maintenance --> RestartAcquisitionPrograms. This just takes a few seconds. It can be really noisy after you do this so you should go to Tune and load vv-now.
NOTE: Always alert Candida Ustine the MEG Engineer before doing this!
Sometimes some MEG channels may look noisy, either with sporadic electronic spikes or be flat, in those cases you will have to Tune the channels. Please do not tune the channels by yourself, please make sure to ask the MEG Engineer for further assistance.