Newbie question - OpenBCI for surface EMG / EEG of cranial nerves?

pycypycy Hong Kong
in General Discussion
Hello,
I'm a complete newbie but I am interested in buying one of the OpenBCI boards for my research project, which involves conducting surface EMG / EEG of various cranial nerves to detect facial movements (ideally also imagined movements).  I've read all the getting started guides and the forums, but I wanted to ask a few questions to check that this is theoretically possible with the OpenBCI boards (or even at all). Appreciate any comments or advice!

1) 8 vs 16 channels:
If I buy a 8 channel Cyton board, can I later buy a second 8 channel cyton board and will that be equivalent to having a Cyton + Daisy board (or can it be easily made to be?)

2) Is there any difference in how the Cyton treats EMG/EEG/ECG signals at the raw signal level?  i.e. can I use all the channels for EMG rather than EEG?  (It appears so from the tutorials?)

3). Is the raw signal coming into my computer filtered at the hardware level in any way?  e.g. are any artifacts (e.g. eye blinks or 50Hz electrical background).  

4) is the Cyton board significantly better than the Ganglion wrt noise?  Seems that there is a difference between reported noise on Ganglion (AD8237) vs Cyton (ADS1299)?
http://alexandre.barachant.org/blog/2017/03/02/Hands-on-OpenBCI-Ganglion.html
vs
http://eeghacker.blogspot.hk/2013/12/self-noise-of-openbci.html

5) which electrodes are most appropriate?  gold or the snap electrode cables? 

Appreciate any advice!

PY

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Py, hi.

    1) the Daisy is not sold separately, so if you want 16 channels you must purchase the 16 channel kit.
    2) all the biosignals are using the same A/D converter; scale factors can be adjusted per channel.
    3) raw output is not filtered or artifacted.
    4) Cyton does have somewhat better characteristics because of the ADS1299 chip. Ganglion has been fixed regarding Alex's article.
    5) snap electrodes will be more comfortable on the face. You can find a range of size and shapes.

    Note that your EMG will be measuring muscle activity, not the cranial nerves directly. Imagined movements are another area called "motor imagery", see this recent thread,


    William

  • pycypycy Hong Kong
    Thanks William for the help and pointers.

    On (1) is it technically and practically possible to have two Cyton boards operating at the same time?  Is there any advantages vs having a Cyton + Daisy?  (I can code, but I'm not much of an electrical engineer).
  • wjcroftwjcroft Mount Shasta, CA
    The 16 channel Cyton+Daisy samples all 16 channels at EXACTLY the same moment in time; by clock synchronization. Two Cytons will have two separate data streams that will differ slightly in synchronization. At 250 hz, one sample happens every 4 ms. Network and serial port delays can also be a factor, so you might see several times 4 ms sample skews. But in your application with EMG, this may not be so critical / important. Exact sync is needed in some types of EEG work, especially those that measure coherence or ERP.

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