Wrong signals which doesn't similar to EEG
Good day all!
We have bought Cyton board at November of 2019. But we can't get EEG signals.
We have tried to connect electrodes according to this manual: https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/EEGSetup
And we have used these positions at a head (10-20 System):
According positions and manual from above we have connected electrodes to pins on the Cyton board in the following way:
AF7 - 1N
AF8 - 8N
F3 - 2N
F4 - 7N
C3 - 3N
C4 - 6N
P3 - 4N
P4 - 5N
A1 (reference) - SRB2
A2 (bias) - BIAS
After this we have seen at GUI signals which doesn't similar to EEG. Also no any reaction on eyes closing. Our doctor (EEG specialist) approved that is not an EEG signal.
I have attached video with signals
Please help us - what are we doing wrong?
Comments
First, check that the power supply is not too low a voltage, and that your settings on the GUI are with proper filters and voltage amplitude scaling. Assuming good power and GUI settings, there may be a problem with some (the reference leads) or all of the leads not having good scalp contact.
Check what happens when you wiggle the wires-- this should cause a brief surge of artifact in the tracing.
If you get that, I would then see what happens if you have someone push down on the scalp leads during recording, to see if this changes or improves the tracing.
Bill, thanks, great points.
Stanislav (ColdDeath), hi.
Has this November 2019 Cyton, ever worked correctly? Assuming you turned it on in 2019, and did the tutorials, did any of the EEG, ECG, EMG signals look ok? The current EEG tutorial,
https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/EEGSetup
Is just two channels using paste. Have you tried that simple setup? Is your 8 channel test above also with paste? Your signals look universally low amplitude, which is usually a sign of a bad reference connection. So ear lobe electrode is especially important and the electrolyte / paste / gel / etc, you are using.
Be sure all the pins you are connecting to, are the ones 'closest' to the board surface, or also called 'bottom' pins.
William
Billh and wjcroft thank you so much for your advices!
I will try all that you have been written above today and will write result.
wjcroft, this board was bought at November 2019 but only recently has been used.
We have checked the following:
As conclusion - no one approach hasn't helped.
Also we have discovered some high frequency noises sometimes.
Any ideas? Please help.
Please try all Cyton tutorials, and report if you see EEG, EMG, ECG as expected. I would first suspect your electrode quality.
https://docs.openbci.com/docs/01GettingStarted/01-Boards/CytonGS
https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/EEGSetup
https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/ECGSetup
https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/EMGSetup
Swap around your electrodes, in case one of the wires or connectors is defective. I would first suspect your reference lead.
If you get a signal with wiggling a wire, check each wire for a signal from wiggling one at a time. If all wires respond to wiggling them, you may either have a skin impedance problem (the electrodes are not making good contact) or the filtering and graph range settings on the GUI are not correct.
We have checked electrodes and wires and get such signals.
Could you see please and say is it more looks like EEG? Video attached.
Stanislav (ColdDeath), thanks.
Your video does look like EEG. However, previously I asked you the below question. Each tutorial shows what the expected signals look like: EEG, ECG, EMG. Performing these simple tests will confirm your Cyton is operating normally with all signal types.
If the leads (wires and electrodes) are ok, check this document: https://www.aset.org/files/public/Skin_Safety_During_EEG_Procedures.pdf