[EEG] low budget EEG project update

Dan Brown danbrown at gmail.com
Thu Jul 22 10:30:45 PDT 2010


Last night Vicente and I met at Noisebridge. We got some data out of
the headset and talked about it, and came up with some ideas for what
to do next. Here's a quick summary and some links to more information
for those interested.

Data validation is an open issue. At times, the numbers coming from
the Neurosky module appeared to be good; reacting to closing eyes and
a few other simple tests. However, they also seemed to generate
similar responses when hooked up to my hand instead of Vicente's (or
my) head. Next steps for this issue: Dan will get another Neurosky
module from a Force Trainer and try to get raw data out of it. Then we
can look at how the raw signal changes when eyes open/closed, or
blinking lights. If someone has a working EEG, that would be a good
benchmark for comparison.

Neurosky does claim to be getting its signals from the brain, and not
from muscles (as the Emotiv headset appears to). Some notes from a
recent talk by the director of tech development at Neurosky claim this
to be true. http://codechix.pbworks.com/f/NeuroSkyEEG.html

The headset is a bit uncomfortable. It's made for kids, and the
elastic strap pushes the metal electrode into the forehead. It would
be difficult to wear it to sleep.

There are 2 different Neurosky modules that are used in products. One
is called the TGAM (ThinkGear ASIC Module), and that is what is inside
the Mind Flex from mattel and the MindSet from Neurosky. The MindFlex
does not generate raw data, the MindSet does. I tried to send the TGAM
from Mind Flex commands over the serial link, but none of the ones I
tried had any effect on its behavior. I wonder if it's pre-programmed,
or hard wired (reversibly?) to not produce the raw EEG signal? I
haven't been able to find any data sheets on this chip. The other type
of module is called the TGEM (ThinkGear EM module, yeah dumb name),
and it may be what's inside the Force Trainer. Instead of the ASIC
chip, it has 2 microprocessors (a PIC and an ATMEGA) and it should
respond to commands to change its behavior. Both types of modules have
5 inputs for the EEG: one for the single electrode, and a pair of
GND+REF for 2 reference electrodes that are meant to be connected to
the person's ear(s). They also both have the 4 wires for power and
serial which I mentioned before. This information comes in part from
the FCC registration docs:
https://fjallfoss.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=N&application_id=258224&fcc_id='PIYP2639-09A5T'
(mindflex)
https://fjallfoss.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=N&application_id=785615&fcc_id='XG9MS1'
(force trainer)

Here's a recent video with presentations from Zeo, Neurosky, and Brain
Fingerprinting Laboratories: http://www.vlab.org/article.html?aid=339

And here's a paper with an interesting way to estimate depth of sleep
in a continuous manner (not epoch-based, not quantized into "stages",
not based on R&K, not based on FFT):
http://www.hsr.nl/bobkemp/papers/2000Microcontinuity.pdf

I will set up another time to meet if/when I have a device that can
generate raw EEG data. In the mean time, I'd be interested to hear any
suggestions from the rest of you. thanks!
Dan



On Tue, Jul 20, 2010 at 9:37 AM, Dan Brown <danbrown at gmail.com> wrote:
> Last week I picked up the parts. The mind flex was $35 at a surplus
> store, and the bluetooth module was $45 (a barebones version exists
> for $25, but for prototyping I wanted it on a convenient breakout
> board)
>
> Yesterday I tapped the serial interface wires on the neurosky eeg
> daughter board in the mind flex headset, roughly following steps 2 and
> 3 from this blog post: http://ericmika.com/itp/brain-hack . I took 4
> wires (+3.3V, GND, TX, RX) and connected them to the bluetooth module.
> Sure enough, data flowed from the neurosky. It is what we expected:
> spectral power bands, meditation, concentration. Although I don't
> expect it to cooperate, I will try to request it to send raw data,
> too.
>
> Today I'm working on writing a python routine to parse the neurosky
> ThinkGear packets, and if I have time I will try to get a graphic
> display working.
>
> ** WEDNESDAY, AKA TOMORROW at 6pm: I'd like your help interpreting the
> data. If you're able to make it to noisebridge between 6pm and 8pm or
> so, you can put on the headset and see your data and then we can try
> to figure out how good it is. If anyone has another EEG device to
> compare, that would be very helpful. Please let me know if you plan to
> be there.
>
> In the near future, I will get one of those other EEG toys, the "Force
> Trainer", which may have a slightly different neurosky module inside.
> If it does, it may be able to send out raw EEG data at 512 Hz, as well
> as the stuff that the mind flex provides. At least, that what the FCC
> registration documents suggest.
>
> Dan
>
>
>>>>> >> While for the Mindflex technically has Bluetooth-band wireless is built
>>>>> >> in, nobody has yet been able to get much use out of it because by default a
>>>>> >> significant portion of the useful data is filtered out before it is reached.
>>>>> >>  The $200 standalone model does have full serial over Bluetooth built in if
>>>>> >> that's what you mean.
>>>>> >> As for the electrodes, from what I've seen it would seem that they aren't
>>>>> >> active (though what I've seen isn't hugely informative on the subject), but
>>>>> >> the amplification/analysis of the system is entirety done inches away from
>>>>> >> them anyway, so you might get some of the advantages of an active electrode
>>>>> >> system.  If you were talking about the same data I'm thinking of, it seems
>>>>> >> that they may have also been using higher quality electrodes, distinct from
>>>>> >> the ones in their actual consumer products, as a proof-of-concept for their
>>>>> >> dry electrode system.
>



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