[FieldTrip] Getting started with realtime EEG data

Sun Mar 3 23:26:15 CET 2013

This is extremely helpful, and just what I was looking for, thank you (both
Robert and Stefan). I have a few followup questions you've inspired.

How "swappable" is the hardware? Do all EEG's fundamentally produce the
same data from the same brain activity? And/or, does FieldTrip always
expose data in its buffer in the same format?

For example, I would be fine investing the $750 for an Emotiv 14-channel
EEG, or even the $1200 for a KT88-1016, but not until after I've done some
development with a cheaper device first. However, I would not want to have
to rewrite all my code, or much of it, if I switch devices.

I do have a requirement that I can have the same code work with either live
or replayed data. From how you describe its buffer approach, it sounds like
that's a core value of FieldTrip, and will make that requirement much
easier to satisfy.

Also, I do have one peculiar requirement, which is that the hardware be
suitable for wearing during ordinary sleeping at home. This is more a
requirement for the final (potentially more expensive) device, than the
development device. The promotional photo for the Emotiv
EEG<http://www.emotiv.com/store/hardware/epoc-bci-eeg/developer-neuroheadset/>,
for example, looks like it might not be so great for that.

I think I will be using WebSockets, but there will be an intermediate
server. So, I will have a computer (perhaps a Raspberry Pi) receive data
from the EEG, and then immediately stream it up an open TCP connection to a
web server. This server will then stream it down to the individual browsers
of visiting users, and JavaScript will do the visualization, in something
like Three.js or Processing.js.

So I don't think I'd be making a JavaScript implementation of FieldTrip,
but I believe the server software could be made to be general purpose, and
reusable in the work of others like yourselves. That would be a satisfying
byproduct.

The idea here is that the resulting website will show fully live and real
time EEG data, specifically while I am sleeping. Since I only sleep for
~1/3 of any given day, the ability to replay things will be helpful in
giving the site utility during the other 2/3.

I've never done any signal processing before, not even so much as a fast
Fourier transform. But I'm willing to learn! I'll be consulting the
tutorial<http://fieldtrip.fcdonders.nl/tutorial> you've
kindly written, but if you have any suggestions of learning material I
should look at when figuring out how to (for example) detect when a subject
has entered levels of sleep given streams of EEG data, it would be a lot of
help to me.

Unfortunately, the paper you linked to (
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8986.2012.01471.x/full) is
behind a paywall and is $35, but if you recommend it highly enough, I'll
check it out.

Again, thank you for being so welcome to a newbie, and for the
recommendations and links.

-- Eric

On Sun, Mar 3, 2013 at 4:58 AM, Robert Oostenveld <
r.oostenveld at donders.ru.nl> wrote:

> Hi Eric,
>
> I think that NeuroSky renamed and discontinued some of their products
> since we made the initial implementation of the ThinkCap.  I am still able
> to find documentation here
> http://developer.neurosky.com/docs/lib/exe/fetch.php?media=thinkcap:thinkcap_headset_user_manual.pdfand
> http://developer.neurosky.com/docs/doku.php?id=thinkcap. I cannot tell
> whether the complete sets now sold by NeuroSky still use the same software
> interface, but NeuroSky is rather open with their development tools.
>
> Alternatives you may consider are the Emotiv Epoc or the DIY OpenEEG. The
> Epoc has more channels and a head mount for the electrodes. For the Epoc
> you have to look into teh different SDK options, the cheapest version only
> gives access to processed data, not to the raw data. For both the Epoc and
> openeeg a implementation of a stand-allone executable is available in
> http://fieldtrip.fcdonders.nl/development/realtime/implementation. LIke
> for the ThinkCap, this copies the data to a "fieldtrip buffer", where
> another (c/c++/java/python/matlab) application can easily read it from and
> do the signal processing, not having to worry about the buffering and data
> representation any more.
>
> I know it falls outside your budget, but have a look at
> http://engineuring.wordpress.com/2009/06/15/writing-your-own-soft-for-a-really-cheap-eeg-hardware-for-brain-computer-interfacing.
> These KT88-1016 systems are available from ebay.
>
> Let me add a bit from the developers perspective and software design. The
> rationale for the fieldtrip buffer is that it allows us to develop analysis
> pipelines using EEG data files on disk (using ft_read_data). Once the
> offline analysis pipeline performs as desired, we just switch from reading
> to disk to reading from the buffer (also ft_read_data). We happen to do
> this using MATLAB for the rapid application development, but the same
> strategy (develop for file, run in real-time) can be used with another
> programming environment.
>
> I think that for signal processing you'll better off if you develop the
> code using some good quality data from a file on disk. You can always enact
> a real-time data stream by replaying data from that EEG file, or using the
> sine2ft GUIs (see realtime/bin). Otherwise you'll be doing all development,
> constantly having to wear the headset. That is fine for artefact detection
> (you can blink while you code), but not if the tasks get more complicated,
> e.g. relaxing to increase your occipital alpha/10Hz won't work well if you
> also have in realtime have to monitor whether your applications picks up
> the alpha.
>
> Some time ago we (i.e. Boris Reuderink and me) looked into the
> possibilities of a web-standards implementation.  Web Sockets would be
> needed in Javascript  if we want to have the browser connect to a
> "fieldtrip buffer" TCP server. The Web Sockets still seemed a bit risky
> w.r.t. it working on all platforms. A server-side implementation offers
> more choice, python/java/php reading the data from a FT buffer or from the
> device, and then pass it on in html format to the connected web ) but would
> not scale as easily with multiple client connections if data processing
> needs to be done on the server. We then considered the best option to  be
> to implement a RESTless server implementation. The server would one the one
> hand contains the FT buffer (where it receives the data over low-level TCP)
> and on the other hand have a web server with the RESTless interface. I.e.
> the requests that are represented here
> http://fieldtrip.fcdonders.nl/development/realtime/buffer_protocol would
> each translate to a http call like "http://ftbuffer.donders.nl/get/hdr"
> and "http://ftbuffer.donders.nl/get/dat?begsample=xx&endsample=xx". You
> can ask Boris (CC) offline whether he has given it further thought.
>
> best regards,
> Robert
>
>
>
> On 2 Mar 2013, at 3:12, Eric Mill wrote:
>
> > Hi all,
> >
> > My apologies if this is off-topic here, since you all seem like very
> busy experts!
> >
> > I'm trying to figure out what I need to get started with capturing
> real-time EEG data using consumer-priced headsets (<$200). I don't actually
> have any interest in using MATLAB, though - I just want to capture the raw
> data, in real time.
> >
> > I see that FieldTrip has a realtime acquisition module for NeuroSky's
> "ThinkCap", though I can't find a current product by NeuroSky called that.
> Is there something else of theirs I could buy that would work with
> FieldTrip?
> >
> > Or, should I be looking elsewhere entirely? What should someone who
> wants real-time EEG data do?
> >
> > My plan is to stream this data and visualize it on the web in real time.
> My background is in web development, not cognitive science, but I'm willing
> to learn what I have to make something interesting. I'd also love to have
> the project result in libraries useful for other people in the field.
> >
> > Thanks for any advice you can give on what EEG to buy, and/or where to
> learn the core concepts I'll need to use the data.
> >
> > -- Eric
> > _______________________________________________
> > fieldtrip mailing list
> > fieldtrip at donders.ru.nl
> > http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
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