Hardware problems and tips for setup problems
This is a list of current and past problems we have had with the neuroscan system.
Current Problems
Past Problems
1. We had a major issue regarding the system. After recieving a "repaired" headbox in April, we began to have intermittent failures of the Aquire program. The program would take about 5 seconds to boot, and when starting acquisition, the program would crash with the error "read data from device." We contacted neuroscan about the issue. They thought it was a problem with the system amp, but the replacement amp had the same problem. We then realized that our problems began shortly after we received the "fixed" headbox. Neuroscan sent us a temporary replacement headbox, and the problem was resolved.
2. The system crashed once at the same time a participant's cell phone rang. We are not sure if this is a coincidence, and related to problem # 1 above, as we have not been able to duplicate the problem. In any case, it may be advisable to ask participants to turn off their cell phones during the experiment.
Tips for Set-up problems
1. All the colors change together
During impedence set-up, all the electrodes may change color together, or it may be hard to get any of them into the blue/black regions. This most likely is caused by the ground electrode. Try to redo the ground electrode, and this problem should go away.
2. Two of the electrodes change together
This is caused by a "salt-bridge", when the gel from 2 electrodes touch each other, creating a bridge between the 2 electrodes. If this happens, note it on the checklist, and try to use less gel. This can be avoided by gently pressing down on the electrode when inserting the gel. This will cause the excess gel to flow out of the top of the electrode instead of spreading on the subject's scalp.
3. The recordings from all of the electrodes are "dirty"
If the recordings from all of the electrodes seem dirty, and they all seem to have the same effect, it is almost certainly casued by the M1 electrode behing the left ear. This is the reference electrode for all cap electrodes, and a problem in M1 will affect the recording from all electrodes. You can easily tell if this is the case by looking at the recording from M2.
4. There is a small "blip" about every second accross all electrodes
This is an example of problem #3 above. In this case, M1 is picking up a heartbeat, and that is being reflected in the recordings of the other electrodes. Usually this occurs when the M1 electrode is placed too low. Re-apply the electrode at a higher point behind the ear.
5. Problems with subjects who wear glasses
Many times the end of the glasses can interfere with the reference M1 electrode. To avoid this, have the subject put his/her glasses on before you attach M1. Then attach M1 so that it is not touching the glasses.
6. Fill the difficult electrodes first
The electrodes around the edge of the head (including O1, Oz, O2, FP1, FPZ, FP2) are often much more difficult to fill than the electrodes in the center of the cap. Fill the outside electrodes first, giving the gel a bit more time to connect while you fill the center electrodes. The outside electrodes will then be easier to adjust if needed.