Polysomnography with Cyton (Sleep research): My proposed setup.

First of all: For anybody looking at sleep research using OpenBCI for the first time, you should first check out SpiSOP:

It is super helpful, particularly for people who already know a thing or two about all this. From what I understand they (he?) will be producing more tools and such down the road, so keep an eye out.  

However, I set up my own Cyton in the way described below because it seems to me to be simply an expanded version of the setup provided in the basic setup tutorial, the logic of which I think I now mostly understand. By comparison, the setup suggested by SpiSOP seemed confusing to a n00b like me because, for starters, it didn’t connect BIAS and SRB to the earlobes as I was used to, but rather to central head locations (Fz and Cz respectively). I know you can use these as references too, but for various reasons I also wanted to have frontal, central and occipital points as suggested by the AASM, rather than just the two central electrodes required by the Rechtschaffen and Kales system. The SpiSOP configuration also has electrodes going from mandibles to regular channels (3 & 4), which I thought was weird - aren’t mandibles supposed to be references? I have since learned (thanks to the SpiSOP people generously explaining it to me) that using software you can change which channel is compared with which other - so that if the SRB2 comes off the head or fails, you can “re-reference” your signal to a different reference (the mandibles on channel 3 and 4). But again as a n00b, I don’t know how to do that easily using the native OpenBCI GUI. SO: The SpiSOP recommended setup unsurprisingly makes a lot of sense (particularly since a Cz reference is less likely to come off than a mandible during sleep), but you have to know a bit more about the software side of things (or just be a bit more familiar with all this stuff than I am!). 

My setup, if correct, should be pretty easy and intuitive for non-specialist beginners to use without having to mess around with any software other than the native OpenBCI GUI. However, it might not survive a full 8 hours connected to a wiggling sleeper, and as I begin to explore other software I’ll likely move to using Cz references and so forth. 

Enough caveats. Here is my proposed setup. Does this seem to make sense to anyone else?

Diagram of setup: https://www.instagram.com/p/Bk5FU50nd5Q/?taken-by=benevansprojects

Explanation and questions:

1) SRB2 is connected to the earlobe or mandible bone behind it and serves as a reference for all the EEG electrodes (3, 4, & 5), just like the "getting started" tutorial.

2) Channel 1 provides the EMG signal, connecting to the MyoWare Muscle Sensor, which is placed below the chin (with the ground/bias electrode stuck on the front below the lip, if it is even necessary?). This channel, I think, compares the data from the top and bottom pins rather than comparing them with the SRB reference, so SRB2 should be turned off in the GUI. 

3) Channel 2 provides basic EOG. Like the EMG, I think this signal compares the top and bottom pins (left and right eyes), and should also have the SRB2 turned off in the GUI. The placement of the electrodes is suggested by SpiSOP - I wonder if it is sufficient? Instead, one channel could be devoted to horizontal (comparing L and R canthus positions) and one to vertical (comparing top and bottom eye placements). Also, I have read that it might be useful, or even necessary, to filter these EOG signals quite a bit? 

4) Channels 3, 4, and 5 provide the EEG signals. They compare the electrode with the A1 (or A2) reference connected to the SRB pin. The default settings on the GUI are fine for these signals .

5) BIAS pins: The bottom one goes to an earlobe or mandible (and, simply put, helps provide a cleaner signal). The top one goes to the “R” connection on the MyoWare device, which is connected to the front of the chin. This, however, might not be necessary, since I've been told that both BIAS pins are the same. I’m not even sure you CAN have two BIAS pins going to different places? So this top pin and it's chin connector (R on the MyoWare) might be best left out?

6) All other pins (grey) are not used. This means three other channels are available for… another EOG (as mentioned above)? More EEG? Backup reference electrodes for eventual "re-referencing"?

Thoughts, ideas, suggestions all welcome. I think mostly I'm confused about the EOG and EMG channels that use both top and bottom pins and what settings they should have in the GUI (i.e. the first tutorial says to remove BIAS from the EMG, but elsewhere I've read that all readings require a BIAS, etc...).