Comparisons with other consumer / commercial EEG devices?

kzzkzz
edited January 2015 in General Discussion
I'd like to use a BCI to play with measuring brain activity, primarily during sleep, and secondarily with concentration, meditation, and relaxation while awake. I'm happy to program, and willing to solder; what I care about is a) data quality, and b) setup time per use.

In terms of data quality, how does OpenBCI compare with dry sensor approaches that are quick to put on, such as the Zeo or http://www.plxdevices.com/product_info.php?id=XWAVESPORT ? Does anyone have noise floor data like http://eeghacker.blogspot.com/2013/12/self-noise-of-openbci.html for them, or a reasonable guess from having used similar sensors?

About how long does it take to connect the electrodes for the electrode starter kit, per-use? Chip's blog suggests that it takes a while, but is that more like 2 minutes or 20? How difficult is it to make the electrodes stay in place while napping?

Any insight would be greatly appreciated.

Comments

  • wjcroftwjcroft Mount Shasta, CA
    edited June 2019
    Kzz, hi.

    It's interesting that both of the headbands you mention (Zeo and XWave Sport) have been discontinued.  I wonder if that may have to do with the challenging aspects of the sensor technology itself, or simply low sales.  Whoever figures out how to do reliable low cost dry active sensors, is going to have a big win.

    If you are looking for sensors adapted for sleep, that seems best done with a dry active sensor approach, since paste or saline-solution passive sensors will dry out in that interval.  But if you are just interested in sensor sites on the forehead, then using the passive "stick-on" Ag-AgCl "dot" snap-on sensors may be a usable alternative.  You can get these cheaply in quantity if you do some web searches.  Your reference and ground connections could be on the left and right mastoids (behind the ear).  I believe the gel inside these and the plastic film covering would keep the sensor hydrated throughout the night.

    Conventional cup sensors used with 10-20 paste can be used during the day.  These only take less than a minute to put on each.  In some medical environments the techs still do a skin prep abrasion before applying the sensors, but this is less needed in this modern era with amps having input impedances of 1 gigaohm (as does the ADS1299 used in OpenBCI).  See:

    http://wwe.eeginfo.com/research/ElectrodeImpedance.pdf

    Another attractive way to go are the saline solution based sensors, such as used on the Emotiv EPOC.  These are just pads which hold moisture between the skin and the metallic electrode.  Before use, the pads are moistened with saline solution, and hold their moisture for an hour or more during use.  Sensors are held on not with paste, but with a band of some sort, such as a headband or velcro band.  Sensor / band mechanics must be arranged such that the band does not wick away the moisture.

    ---

    Regarding data quality, I don't know of any other consumer grade equipment that has the research / commercial grade amp we are using, the TI ADS1299.  24 bit samples, programmable gain and sample rate, delta-sigma ADC design, sensor location flexibility, on-board programmability.  Much of the consumer gear has fixed 10-20 locations and only a few sensors, closed source approach, etc.

    William
  • Hi Kzz,

    Electrodes are (IMHO) the hardest part of getting a reliable EEG setup.  Sleeping might be one of the hardest scenarios of all, given the long duration (hours) and given the fact that you're laying your head on top of some of the electrodes, which will try to move them around, which is a bad thing.

    William's suggestion to start with the stick-on electrodes is definitely the right thing to do when you're getting started.  They're quick, cheap, and easy.  As William said, the main down side is that you can only attach them to places with no hair (like your forehead).  But, by starting with these easy electrodes, it'll let you work out all of your other issues such as...can you really sleep with all of these wires coming off your head?  How do you manage all those wires?  Do you get tangled up?

    When you get those issues addressed, you can move on to other electrode types with more confidence that the effort required to put them on your scalp will be paid back with a good overnight recording.

    And, to answer your broader question, your only real option for electrodes (as a consumer) are traditional wet passive electrodes.  The world could really use a low-cost, open-source dry active electrode, but as far as I know, they just don't exist.

    Good luck!

    Chip
  • edited January 2015
    Emotive EPOC vs. OpenBCI, features?
  • wjcroftwjcroft Mount Shasta, CA
    Here is a great review paper on 4 commercial EEG systems that came out summer of 2014. @ratlabguy is the lead author,

    http://iopscience.iop.org/1741-2552/11/4/046018/pdf/1741-2552_11_4_046018.pdf


    Usability of four commercially-oriented EEG systems

    US Army Research Laboratory, Human Research and Engineering Directorate, Translational
    Neuroscience Branch, Aberdeen Proving Ground, MD, USA

    Human Neuromechanics Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI,
    USA

    Abstract
    Electroencephalography (EEG) holds promise as a neuroimaging technology that can be used to understand how the human brain functions in real-world, operational settings while individuals move freely in perceptually-rich environments. In recent years, several EEG systems have been developed that aim to increase the usability of the neuroimaging technology in real-world settings. Here, the usability of three wireless EEG systems from different companies are compared to a conventional wired EEG system, BioSemi’s ActiveTwo, which serves as an established laboratory-grade ‘gold standard’ baseline. The wireless systems compared include Advanced Brain Monitoring’s B-Alert X10, Emotiv Systems’ EPOC and the 2009 version of QUASAR’s Dry Sensor Interface 10–20. The design of each wireless system is discussed in relation to its impact on the system’s usability as a potential real-world neuroimaging system. Evaluations are based on having participants complete a series of cognitive tasks while wearing each of the EEG acquisition systems. This report focuses on the system design, usability factors and participant comfort issues that arise during the experimental sessions. In particular, the EEG systems are assessed on five design elements: adaptability of the system for differing head sizes, subject comfort and preference, variance in scalp locations for the recording electrodes, stability of the electrical connection between the scalp and electrode, and timing integration between the EEG system, the stimulus presentation computer and other external events.
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