Failing to see any SSVEP. Is my raw data bad quality?

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Comments

  • Actually, I meant just wrapping the Arduino in foil. It is physically separate from the OpenBCI.

  • Thanks for your feedback as always.

  • wjcroftwjcroft Mount Shasta, CA

    Because of the oxide layer formed on aluminum, making grounded connections to such foil is daunting.

  • Ah I understand. Maybe the stimulus box will have to have multiple layers.

  • wjcroftwjcroft Mount Shasta, CA

    I do not think you will need any shielding. Try that first.

  • edited November 2022

    I've heard from other researchers that they needed shielding with OpenBCI, so I am curious in which circumstances one does or does not need shielding.

  • Maybe with high-frequency stimulation?

  • skidrowicskidrowic United States
    edited June 24

    Hi Wj and Matt, I find myself with a similar problem as you guys, but was not resolved after making sure the pins on my board were in the down position. When I record close-eyed data I fail to see a consistent peak at 10hz, and here is a video link of the OpenBCI GUI output:

    I'm not using the 4th channel, and I'm sitting with my chip pretty far from my laptop and desk, and have tried lots of different combinations of filtering/ denoising. Let me know if you might have any insight into the issue. Thanks!

  • wjcroftwjcroft Mount Shasta, CA

    @skidrowic said:
    ... When I record close-eyed data I fail to see a consistent peak at 10hz,

    Hi SkidRow,

    I'm not sure why you are commenting on this SSVEP thread. Eyes closed alpha is not the same as 'visual evoked potential' (VEP) issues. Best alpha production is on electrodes in occipital or parietal sites. Some people generate more than others, so suggest trying with a friend you connect up.

    William

  • skidrowicskidrowic United States

    Hi William,
    Thanks for your response, apologies I was doing the eyes closed alpha test since I read earlier in this thread you recommending Matt to do the same to see if he gets a peak at 10 hz. I've been using my computer monitor to flash at 13 hz, and used a photoreceptor detailed on mind affect's page to make sure my screen is flickering accurately. However I still get charts that, similar to matt, have large jumps in amplitude. I will try the closed eyed test on another individual to see if they have a more defined peak at 10. Here is a raw eeg plot, and the corresponding fft plot:

  • wjcroftwjcroft Mount Shasta, CA

    The 'fuzziness' shown in your red, blue, green, orange plot above looks to be mains noise. Yet your Youtube video shows you have your notch set at 50 Hz. Mains frequency here in the US is 60 Hz. You need to change the notch.

  • skidrowicskidrowic United States

    I've adjusted my notch to the correct value of 60, but still got no real peak. Here is a recording of data where my eyes are closed for 10 seconds. I've also attached a link to my python script as well. Thank you again for any help I greatly appreciate it
    https://drive.google.com/file/d/1_cYsEqgHkOUW9NFnQC4UrJHF1C23ErCf/view?usp=sharing

  • wjcroftwjcroft Mount Shasta, CA

    Suggest perhaps working with a friend and have them close their eyes while you watch time series and FFT. The above time series is 700 seconds long. So your 10 second eyes closed is lost in that ocean of eyes open. The blink artifact does not help.

  • skidrowicskidrowic United States

    Ok sure, apologies for the confusion the x axis is data points so the recording is around 3-4 seconds, will try with a friend and perfom ICA to remove blink artifacts

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