multi person, multi channels SSVEP on OpenBCI

SeventeenChenSeventeenChen Shenzhen
edited July 8 in Cyton
Hi, everyone, 
We have tried to observe multi-channels SSVEP on computer with Cython, the details of our experiment are following:
1. two people , channal 1 and channel 2
2. Oz, Cz, AFz; Oz is the measurement connected to N1(N2 fot the other), Cz is the reference connected to P1(P2), AFz is GND connected to BAIS. The connection is like 'Shark Attack' experiment.
The question is:
We found the signal in one channel could influence the other, which should be calculated individually, for example, if we found a peak in channel 1, there could be the same peak in channel 2, but the peak shouldn't appear in fact. Why does it happen? How could we analysis the mutili-channal SSVEP individually with Cython?


Regards,
Chen

Comments

  • Usually the peak that should not appear in more than one place is due to a change in the surrounding environment that affects both persons, and multiple leads and channels. There is also some possibility of cross talk between channels. The crosstalk should be removable by subtracting Cz from Oz on each person.
  • wjcroftwjcroft Mount Shasta, CA
    Bill, thanks.

    Chen, hi. Have you adjusted your OpenBCI_GUI settings to disconnect SRB2 (and SRB1) from the common reference bus? And also disabled the Bias (inverse common mode signal) injection? I think in your case you only want to use Bias as a ground, and give up on the common mode injection, since you are using two subjects. I believe Chip's Shark Attack setup used such settings. If you are not receiving the data with the GUI, (for example Python), then you need to send the appropriate SDK serial port commands to affect these settings.

    Regards,

    William

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