2*10 pin cables but only 8 or 16 channels ? [resolved]
EstherBarnaul
Cologne
Dear all,
I am in the process of setting up the board. I have two electrcables and would like to put the header termination in the bottom pins. However, there are 16 bottom pins (8 in Cyton, 8 in Daisy) but ten female header terminations on each of the two cables. Which terminations shall I use, and what do do with the two that I cannot connect?
Thanks a lot
Esther
Comments
Esther, hi.
Have you looked at the Daisy tutorial?
https://docs.openbci.com/GettingStarted/Boards/DaisyGS/
Besides the 8 channels (each on Daisy and Cyton), there are also Bias and SRB (reference) connections. For example with Ultracortex headset, Bias goes to one earlobe, and Reference to the other. If you are using an electrode cap, you can choose if you want to use the Ground / Reference locations on the cap for these extra leads, OR, you can use your own earclips.
William
I looked at the tutorial, and there it says that I should use the eight channels. The (upper) SRB is already used for the cable that connects Daisy and Cylon. It is probably not important which colour is used for which channel, and maybe I will need to disconnect the cables from each other anyway. I only have the tendency to decide on e.g. simply taking two cables out, only to learn later that it is not allowed to simply take them away.
Do you know whether there is a video presenting how everything is done and connected? For me as a non-native speaker more pictures could be very helpful because sometimes I am not sure whether the thing in my hand really is the thing named in the text.
Are you using an electrode cap? See this related recent thread,
https://openbci.com/forum/index.php?p=/discussion/3092/mapping-for-connecting-electrode-cap-positions-to-channels
The two LOWER SRB2 pins are connect to a Y-cable, the male pin connector of that Y is then your REFERENCE electrode. YOU get to choose what reference location you use. Some use an ear lobe. If you have the cap, it has a Reference electrode that is not on the 10-20 layout. Similarly Bias can either be the other ear lobe, or the Ground position on the cap.
Thanks a lot. I think my question is much more basic than this. I have this device:
https://github.com/openbci-archive/Docs/blob/master/assets/images/touch_proof.jpg?raw=true
and it has ten terminates. In this picture:
https://github.com/openbci-archive/Docs/blob/master/assets/images/MarkIV/Cyton_Daisy_Setup.JPG?raw=true
it is eight terminates. So my very basic question is: Can/or should I disconnect the single cables from each other and simply put the extra two cables aside?
I know that this sounds rather very, very basic, but since I am alone with this thing (my colleagues do not work with EEG or any other electronic device that needs putting together), I am nervous of destroying everything by taking the wrong devices...
You can separate ribbon cables however you like. There is no interconnections between the wires in the ribbon.
As mentioned previously, you will still need 2 extra wires for Reference and Bias (Ground).
I asked before, are you using an electrode cap?
Sorry, yes I am using an electrode cap.
Stupid question: the extra wires for Reference and Bias are not the y-cable?
The Y-cable joins the TWO SRB2 lower reference pins (one from Cyton and one from Daisy), into a SINGLE reference pin. You still need to connect the reference to the subject. As mentioned, this can be done either through an ear clip (if you have one), or the 'Ref' location on the cap.
Similarly, the Bias pin from Cyton (all 4 Bias pins are the same signal), must be connected to the subject. This can be done either with another ear clip, OR you can use the 'Ground' / GND, location on the cap.
Thanks a lot! I will try this out and will let you know how I managed to do it. Hope it will be a a picture of a happy person.
Hello, me again.
I have now (hopefully) connected everything correctly. However, the cap comes with 19 electrodes (and cables respecitvely, but the board only offers 16 connections. Is this correct? If so: how do I decide which electrodes to use?
Thank you very much,
Esther
@EstherBarnaul, hi.
I merged your new thread into this existing thread on the same subject. Did you see the previous diagram link I posted?
https://openbci.com/forum/index.php?p=/discussion/1087/connecting-mark-iv-to-cyton-including-daisy-board/p1
That diagram shows the default 16 channel GUI 10-20 mapping. You can choose to follow this, or use your own setup.
William
Dear William,
Thanks a lot. Just to make sure: This means that basically three electrodes on the cap will not be connected to anything?
And before I set up another new discussion: do you know which of the electrodes are best for n400 and p600 tests?
All the best,
Esther
Yes, the 10-20 standard is 19 channels. EEG chips such as the Texas Instruments ADS1299 (used in Cyton) have 8 channels each.
https://en.wikipedia.org/wiki/10%E2%80%9320_system_(EEG)
This page mentions where the P600 EEG source generators are located:
https://en.wikipedia.org/wiki/P600_(neuroscience)
Similarly,
https://en.wikipedia.org/wiki/N400_(neuroscience)#Sources
I'd suggest consulting papers measuring these waves, to see what setup they used. As you know, in addition to the 10-20 map, there is also the 10-10 system, which interpolates between 10-20 points. Links above mention central-parietal locations, which have a row in the 10-10 system. But your cap is setup for 10-20, so just approximate. These links also stress that the sources are distributed, so exact scalp positioning is less important.
https://en.wikipedia.org/wiki/10%E2%80%9320_system_(EEG)#Higher-resolution_systems
Thanks a lot again. I hope I will be able to get into this and to work sensibly...
There are no courses you give, by any chance. As mentioned in another post, my problem is that I am the only one around working with EEG (in fact, I am the only one working empirically. My colleagues are pure theorists).
Have a nice day!
Esther
re: online training
JoVE has some EEG material. Try your own search terms,
https://www.jove.com/search?q=eeg
Great! Thang you very, very much!
https://www.jove.com/v/10275/language-the-n400-in-semantic-incongruity