Ultracortex Mark IV vs Gelfree Electrode Cap?
I have some grant money (€2400) that will expire at the end of the month and I want to buy an EEG system to test some research ideas. I have searched many different distributors, and it seems that I can get the most channels with OpenBCI. I also like open source projects in general, so I want to support their ideals.
However, I cannot decide on whether to get the Ultracortex Mark IV or the Gelfree Electrode Cap. I would get the 16 channel variant of either that includes the CythonDaisy board. What are the pros and cons of each? I lean towards the Gelfree Electrode cap because it looks nicer, but the Mark IV has more electrode position possibilities. Would both work during VR? What about during navigation outside? Since both connect to the same board, I would think they are the same in this regard.
Could I measure ERPs with either of them or is the dry cap technology not sufficient? I saw one study where ERPs could be measured from Muse, so I would assume both of these would be sufficient.
Would either of them work with the ThinkPulse Active Electrodes if I decide to upgrade?
Any advice would be highly appreciated.
Comments
Hi Dustin.
Sorry for the delayed response.
re: comfort / accuracy during navigation outside.
Wet electrodes systems, such as the Gelfree / saline cap, or gel based systems, are generally less prone to motion artifacts and modest head movement. This is because the water based electrolyte / skin interface is less subject to pressure differences from modest head motion. The heavier Mark IV headset has a certain 'inertia' that may result in differing electrode pressures when in motion.
In terms of comfort, note that the dry electrodes of Mark IV, (cones, and combs) are hard silver chlorided plastic, thus more noticeable pressure points on the scalp. VR headsets may be uncomfortable with either the Gelfree or Mark IV, due to positioning of the VR unit straps and face / eye mounts. But workarounds may be possible. It seems likely the Mark IV would be harder to adapt due to the overlap of the VR head mount with the front portion of Mark IV.
re: Thinkpulse Active (soft rubber) electrodes
These only work with Mark IV. But signal quality with the Gelfree should be similar. Note that with the default Mark IV headset (no actives) signal amplitude is generally slightly less than with wet or active based systems.
William
Curious on the pros and cons of each system. It seems like there are way more projects for the ultracortex but the gel free cap seems like it would be slightly more accurate and comfortable to wear.
@ronykrell, hi.
I merged your new thread into this existing thread on the same topic.
William
Thanks, this is super helpful! I noticed there seem to be a lot more projects out there that used the Mark IV than the gel free electrode cap. Are the systems similar enough that tutorials / knowledge articles on the Mark IV are transferable to the cap? Are there dedicated sites / resources to support for the cap?
This is because the Mark IV has been available for many years, while the gel-free cap is a newer option. The Mark IV is great for many quick sessions and if you are also working with a smaller team (or even individually). The gel-free cap is easier than the gel-required caps because the setup time is less, and won't leave a small mess in your hair. Caps are generally better if you plan to do longer sessions (1hr+), and they may also work while doing sleep recordings. The MarkIV is best for awake recordings, and if someone breaks the headset (though this is pretty hard to do) it could easily be remade using a 3D printer. Certain parts on the Mark IV, like the electrodes, are not 3D printable and come with the "print-your-own" kit.
At OpenBCI, we want everyone to be able to learn and develop solutions using Brain Computer Interfaces. To make this a reality, we help by providing open-source software and hardware in a modular fashion.
The Cyton board can connect to both wearable options, and working with this on the software side is exactly the same. The biggest difference between the cap and the Mark IV would be that the cap potentially offers a better connection via the electrodes based on your planned activity and hairstyle.
BTW, here is a searchable list of many published papers using OpenBCI technology: https://docs.google.com/spreadsheets/d/1WvolD2-QJ5aUJy5o0Dq5wdFQtLMkMtppZT8s_ihYyA4/edit#gid=0 .
Take Care,
RW