MNE montage for UltraCortex IV setup

Hi all,

I use MNE in my 'day job' working with EEG signals in a research facility and I'm starting to play around with OpenBCI at home. I've loaded some raw data into MNE and I want to set the montage correctly so that I can colour-code the traces and start plotting topographies or sensor-locations to be able to better inspect the data coming out of the headset. Is there a custom montage for this headset? In the OpenBCI_GUI it displays the electrodes in the correct place, but I'm a bit lost in where this data resides and in what way I can "inform" MNE about this to have the regular colour-coded sensor locations visible.

Thanks in advance for any hints and help.
Alex

Comments

  • I seem to have posted this in the Software section. I meant to post this in the Electrodes section. Sorry about that.

  • retiututretiutut Louisiana, USA

    In the UC Mark IV doc, there is a default electrode configuration and a table that lists the positions.

    https://docs.openbci.com/docs/04AddOns/01-Headwear/MarkIV#electrode-location-overview

    You are free to change electrode positions to whatever suites your needs, though the Headplot widget in the GUI is not customizable at this time. The GUI and BrainFlow keep track of channel numbers associated with the ADS1299 pins for the sake of simplicity.

    For GUI 5.0.4, data recordings are stored in [USER]/Documents/OpenBCI_GUI/Recordings with no specific information on anatomical electrode positions. If you save the data as BDF, I think you may be able to add this extra information afterwards. We are considering ways to improve how data is stored. https://github.com/OpenBCI/OpenBCI_GUI/issues/966

    Hope this helps,
    RW

  • Hi RW!

    Thanks for the links. I'll check out the Github and see if there might be any further issues I might be able to help with once the teething problems are all sorted. I had trouble getting the montage correct but then I realised I wasn't setting the board_id correctly. It worked initially, but then it stopped and I hadn't realised I wasn't specifying the correct board_id for the Cyton+Daisy ("2") and once I did that, then mne.channels.make_standard_montage('standard_1020') worked as expected after resetting the montage on top of the RawArray data structure did the trick.

    So, if I understand you correctly, each of the pins on the board is associated a priori with an electrode location (i.e. T7)? I know in the documentation it said it was pretty liberal and there probably is a way to reset it, but at least without making any of those changes, there is an understood "default" convention?

    Thanks!

  • retiututretiutut Louisiana, USA

    The GUI and BrainFlow keep track of channel numbers associated with the ADS1299 pins for the sake of simplicity.

    Expanding on this note, I mean that Channel 1 on the Cyton will be Channel 1 in BrainFlow, the backend software to handle communicating with the board. I think you may be looking for something like this? https://mne.tools/dev/auto_tutorials/intro/40_sensor_locations.html#about-montages-and-layouts

    @algmur You may need to make a custom "MNE montage" for the default Mark IV electrode positions. If you do, maybe you could share here what others should use or other advice for MNE.

    Take Care,
    RW

  • retiututretiutut Louisiana, USA
    edited April 28

    Here is a side by side comparison of the default/recommended 16 ch setup with Mark IV and the BioSemi16 built-in montage.
    :)

    OpenBCI Default 16 Ch Mark IV (shown in Docs). Has electrodes around the head, but not on the midline.

    BioSemi Cap 16 Ch Montage (16 channel MNE built-in montage). Includes some electrodes along the midline.
    https://www.biosemi.com/headcap.htm
    https://mne.tools/stable/generated/mne.channels.make_standard_montage.html#mne.channels.make_standard_montage

    So, if you like the BioSemi built-in montage shown, you can move the electrodes on the Mark IV and make sure to plug electrodes into the correct channel (marked A1-A16 which would correspond to Cyton-Daisy channel numbers). Custom electrode positioning is a strength of the Mark IV headset.

    RW

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