recommendations for research material by electrode location?

[cycon]

Hello all.

I am an experienced developer, looking to get more involved with BCI.

I have access to an Emotiv EPOC headset with ability to access its Raw EEG signals through their SDK, and going by this forum post, will soon be able to tie that together with the OpenViBE software suite.


Unfortunately however, the key Cz, C3, and C4 electrode locations (going by the 10-20 scale) for P300 and right/left/feet motor control are not available on the Emotiv hardware. Instead their hardware provides electrodes in the following 10-20 locations:

AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6, F4, F8, AF4


My understanding, based on discussions with Emotiv, is that they designed their headset with as many unique channels of information as possible, at the best price/feature ratio, which would fit the most number of potential users in a one-size-fits-all form factor. This last restraint prevented them from Cz, C3, and C4 because the exact locations from user to user were not consistent enough to be relied upon in a consumer setting (their target market). Locations for an adult would not be the same as an adolescent user, and getting the locations lined up precisely is "too hard" for the casual or non-technical public.


So the question I'm getting at, is what resources and methods can the OpenViBE community recommend for me to search, find, and review research papers and similar published material which will help me to learn what sorts of signals and information I can pull from those specific electrode locations, in order to reproduce and contribute to interesting work in the field of BCI?

I have a few Neuroscientist friends who can help me get access to various peer-reviewed journals, however I first need to be able to tell them which papers I am after - and that's where I am having a tough time.

How can I best learn what a given electrode is known to be able to measure versus another?

What forums, mailing lists, or other online resources can OpenViBE users and developers recommend?

What are the methods which someone like myself - who is better versed in software development than neuroscience - might apply to learning more on the research and academic side when we are not currently part of those communities?


Cheers

Steve Castellotti

[nbaron]

Hello cycon

Like you, I am "better versed in software dev than neuroscience"
In the beginning of the year I worked on a BCI project and I tried to found as many information as possible.
I can advice you to look at :
[*]here, OpenVibe wbsite
[*]OpenEEG website and mailing list
[*]Those articles ==> http://www.biosemi.com/publications/ (artikel1..8.html)

Hope it will help !

[yrenard]

Dear Cycon,

I recommend that you read the following article which is an excellent introduction to the field of BCIs.

Best regards,
Yann Renard

[cycon]

I recommend that you read the following article which is an excellent introduction to the field of BCIs.

Yann-

Thanks for that. I'm familiar with Wolpaw's work at Wadsworth, it was a BBC article several years ago posted to Slashdot which first introduced and got me interested in BCI.

The full content of that original journal publication referred to by the article is still freely available online here:

Control of a two-dimensional movement signal by a noninvasive brain-computer interface in humans


I've put in a request for your suggestion in the meantime, many thanks for the recommendation.


Cheers

Steve Castellotti

[cycon]

I recommend that you read the following article which is an excellent introduction to the field of BCIs.

I've put in a request for your suggestion in the meantime, many thanks for the recommendation.

Thank you once again, that article was a great help. I think I'm starting to better understand the basics.

Since its review I have found at least one paper which describes being able to pull P300 data out of the Emotiv headset specifically (available online here) though granted with only up 88.9% accuracy in the best circumstances (dropping between 66.7% and 77.8% in less favourable conditions).

I am now working my way through Farwell and Donchin's 1988 paper which first introduced P300 use for BCI applications, and hoping to combine it with Schalk et al's 2000 research into the "Error Potential" to increase selection accuracy (even though that researched was focused on mu and beta rhythm control as opposed to P300 detection).

If anything all of the reading I have done has pointed to more and more research focusing on sensors aligned along the longitudinal Nasion-Inion line, everything from Fpz being used to eliminate EOG noise, Cz for mu and beta rhythm measurements (along with C3 and C4 as mentioned above), Cz and Pz being recommended for P300 measurements, Cz yet again for Error Potential recordings, and Fz and Oz being used to help with spacial filtering. None of which are available on Emotiv's hardware, nor any other commercial headset offerings.

I suspect I will have to look into building a modularEEG (based on OpenEEG designs) if I want to get into any more complex work, though that would defeat most of my projects' goals, which are centered around general-purpose and easily-accessible hardware.

In any case I would still appreciate further recommendations, especially anything utilizing the sensor locations have access to with consumer-grade hardware.


Cheers

Steve Castellotti

[Stefanj]

Hi Steve

One thing that professionals will always tell you is NOT to mix EEG electrode types. For instance, don't mix Ag/AgCl with solid silver or gold electrodes, etc. The reason is that this would create large DC offset potentials which your EEG amplifier would have problems in dealing with. Ideally the electrodes should be from the same supplier and be of the same age.

The Emotiv however, has coupling capacitors right at it's input (this is quite different from any modern EEG amp I have ever seen) and the above mentioned rule therefore doesn't apply.

It would be quite feasable to unplug one or more Emotiv electrodes, make your own substitute "plug" and run a small extension wire to extra electrode(s) which you would then be free to mount where you wanted to.

This problem and my suggested solution has nothing to do with electronics, but rather it becomes a mechanical and implementation challange. For instance, you could go buy standard Ag/AgCl electrodes and attach them with gel and/or some band.

A bigger challange would be to make your own "electrode plugs". A broken, discarded Emotiv would be ideal. I think you could even buy replacement electrodes from Emotiv. You would have to solder the extension wire to the metal contact. You would need a small soldering iron and be quick with soldering, otherwise you would melt the plastic.

You could even go one step further and make your own substitute saline electrodes. Find a small cap from a bottle, or something similar, and cut it down so that it is shallower. Find a small piece of tin and cut it so as to fit inside the cap. Best would be to solder the perimeter edge with solder so as to prevent rusting. Solder a suitable wire to the tin and run the wire through a little hole you punched or drilled into the cap. Now glue the piece of tin to the cap bottom. Finally insert some cotton wool and moisten with the same saline solution you use to wet your Emotiv electrodes.

Regards
Stefan