SSVEP and Acceptable Ranges for Railing Percent

dcgainesdcgaines Houghton, MI, USA
edited January 15 in Headware

Hello,
I recently purchased an OpenBCI system and am currently trying to start with using SSVEP. So far I have been unable to see a consistent spike in the FFT plot in response to stimuli. I tried looking through past forum posts but most pointed to the MindAffect GitHub repo which does not appear to be active anymore. I've begun to suspect signal quality - we are sometimes able to see the alpha wave at 10Hz but I'm not sure how prominent it should be. Most channels are showing a railing % of 30%-50% after adjusting the electrodes (dry combs). Is this in the acceptable range, or is there a problem we still need to fix? I see a lot of threads on how to fix railing, but not many mentions of what ranges I should be looking to get these to.

Thanks!
Apologies if this is in the wrong category, I can't find a way to change/delete it

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Hi DC,

    @dcgaines said:
    ...
    I recently purchased an OpenBCI system and am currently trying to start with using SSVEP. So far I have been unable to see a consistent spike in the FFT plot in response to stimuli.

    Please read this recent comment on the other SSVEP thread:

    https://openbci.com/forum/index.php?p=/discussion/comment/21024/#Comment_21024

    I tried looking through past forum posts but most pointed to the MindAffect GitHub repo which does not appear to be active anymore.

    MindAffect Github is here at the moment, is is far superior to SSVEP.

    https://github.com/wjcroft/pymindaffectBCI

    I've begun to suspect signal quality - we are sometimes able to see the alpha wave at 10Hz but I'm not sure how prominent it should be. Most channels are showing a railing % of 30%-50% after adjusting the electrodes (dry combs).

    Railing issue the dry passive electrodes discussed here:

    https://openbci.com/forum/index.php?p=/discussion/1481/how-to-become-de-railed

    And the first link I gave above mentions that most success with SSVEP or cVEP is with wet electrode systems, due to increased signal levels there.

    Regards, William

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