alternative electrodes, to avoid paste allergy ? [resolved]
Lisoosh
New York, NY
Hello all!
I’m so happy to find this amazing forum. I’ve recently discovered neurofeedback as I was looking for a resource to help my sister and dad, who both have intense mental health challenges. But as we’ve explored this, I’m realizing that for me and for others in my family, it’s such an amazing form of self development and support! Really a gift.
For my dad and sisters immediate support, we rented a home system called Neuroptimal. Though we are really interested in other forms of neurofeedback, this seemed like a good intro. But unfortunately with the system, unfortunately we’ve had a problem where the paste used for the electrodes, give my mother a local allergic reaction. We asked the trainer who rented us the system, and he said that it’s impossible to either use a different paste or change electrodes or anything else. But I wonder if perhaps he might just not be so knowledgeable about hardware and creative approaches to this.
I wonder if anyone here might have any advice? Is it possible to just switch the electrodes, like to plug in different wires into the amplifier? Or any thoughts on electrodes that might be less allergenic – like electrodes that might not need the paste? The locations for the Neuroptimal system are three sensors on the ears, and two sensors on the side of the head.
I’m really excited to hear all of your thoughts! This is such an amazing journey, with neurofeedback. My dad and sister are somewhat incapacitated these days, but they were a computer programmer and a electrical engineer in the past. I love the idea of us getting to experiment with how technology can support the brain.
Thank you all for your thoughts!
Best,
Lisa
Comments
You could try small gauze squares wet with a supersaturated solution of table salt, especially if the leads are clipped on (since the gauze will not be sticky as the paste is). Put the damp gauze where the paste would be.
There are few things less likely to cause allergies than salt, but if that does not work, there are also gels such as the ones used for ultrasound machines that are conductive you could test for allergies on her instead of the paste.
Ohh!!! So cool! Genius!
How supersaturated does it need to be? Is it irrelevant how supersaturated as long as it is supersaturated? (Sorry if this is a dumb question, I’m obviously not the scientific one in the family).
the more salt in the water the better it conducts, but otherwise it does not matter. Silver solutions are better than sodium, but all work.
Bill, thanks.
Hi Lisa,
There are a number of commercially manufactured 'saline EEG' systems. Here are a couple examples. First one is called Free-Cap:
https://www.neurofeedback-partner.de/product-161.html?language=en
That one uses the more expensive (and temperamental), sintered silver chloride electrodes. NeurOptimal just uses plain silver cup electrodes. You could ask if you could lower the price by using your own silver cup electrodes and drop the sintered. Very simple setup as you can see. Just elastic bands held by a chin strap. You position the sensors at the desired 10-20 scalp positions. For NeurOptimal, I believe the scalp sites are C3 and C4. With linked ear references and ground connection.
Greentek is another option that uses a cap instead of bands. But is likely overkill for NeurOptimal.
http://www.greenteksensor.com/
I see OpenBCI is listed at the bottom of that page. We have an old thread on the forum with one or two users trying it. But there is lots of superfluous material in that thread as well (such as meditation discussions). So poor signal to noise ratio.
https://openbci.com/forum/index.php?p=/discussion/1663/greentek-gelfree-s-eeg-cap/p1
These both come with instructions on proper salt solution ratios. Full 'super-saturation' is generally not needed. My understanding from talking to OpenBCI staff, is that they are considering offering a saline cap in the OpenBCI Shop possibly at some point in the future. Not sure the timeline. I'm pretty sure the Free-Cap would be lower priced, since it is only two channels. Whereas Greentek is the full 19 channels.
Regards, William
This is amazing information!! I will review all these options. It's great to know they are there. Thank you so very much!!
As you can see, the idea with the Free-Cap, is just an elastic band arrangement. Since you know your NeurOptimal just uses scalp sites C3 and C4, it may be possible to rig up your own elastic band which goes under the chin / over the ears. Then as previously mentioned small pads or sponges could hold the saline solution under the cups.
In any EEG done at sites with hair (such as C3, C4), it is important to part / move / push the hair out of the way at the site, to allow a closer contact between the electrode (plus sponge) and the direct skin. Without pushing the hair away, it would make a poorer EEG recording.
Here is a link to a Velcro One-Wrap saline headband tutorial I made some years ago. Still use it. Although it's fairly geeky to setup and maintain. You would be better off with a commercially made device.
https://sites.google.com/site/biofeedbackpages/velcro-saline-sensors?authuser=0
And on that same page, I have a sub-page listing various commercial saline systems. Not exhaustive, but covers many of them.
https://sites.google.com/site/biofeedbackpages/velcro-saline-sensors/commercial-saline-sensors?authuser=0
William
Hi William and all,
Sorry for my late reply to all this wonderful information. I am realizing some of the hardware is a little out of my depth-- I'm just not sure what things to buy to replicate the Neuroptimal sensors, so I'm thinking to start small with the saline suggestion.
I wondered, rather than use gauze with saline, do you think it would be sufficient to use a saline gel, like this:
https://bio-medical.com/cg04-saline-base-signa-gel-8oz-tube-2-pack.html
And to just use that with the electrodes provided by Neuroptimal?
With some attacher, like the DrDiane velcro 2 channel Neuroband to hold the two sensors at C3, C4 (https://www.drdiane.com/product/2-channel-neuroband/)
I'd love to know if you guys think that would be an okay way to try it. I actually did call both the psychologist who rented me the machine, as well as Neuroptimal themselves, to ask about this. I was very sad that they both said, it can be only be used with their sensor technology.
NeurOptimal uses cup electrodes which are held to the scalp by the adhesive properties of the conductive paste. Saline gels or liquids have no adhesive. Thus you need some type of band to hold in place.
The DrDiane mentioned on my commercial saline list is the LEAST recommended system. (Cost and poor quality animal skin pouch material.) The list mentions those downsides.
Any type of elastic band material might work. C3 and C4 are over tops of ears. My own saline velcro system uses the Velcro brand One-Wrap, which is hook on one side and loop on the other. If you first place a band around the forehead (loop side inward), that leaves the hooks facing out. And thus can adhere to a loop going over top of the head. Again loop facing in. A chin strap can help to stabilize the 'hat band' around the head circumference.
The gauze or Sham-Wow chamois is still a good way to have the saline held between the cup and the scalp.
This is BS, they are clearly unfamiliar with the many many other manufacturers offering saline systems. In fact you WILL be using the exact same cup sensors with this saline setup. It is just that you will be using saline pads instead of paste. Exact same EEG electrical characteristics.
Yes I thought so!! I was really disappointed, as it seemed like either ignorance or professional business interest.
Great to hear this about the saline!!
We are still figuring out how to hold the sensors in place on the head, if we are using the saline system. I like the Velcro system you are describing! My mom was curious if she could use the conductive paste on the head and the saline on the ears-- since she only had the allergy on her ear, not head. But, I thought that would be a problem for the system, if they have different conductivities. What do you think?
My mom is all set with Velcro one-wraps, supersaturated salt solution and Shamwow
We are so excited.
What do you think of this saline gel as well?
https://bio-medical.com/cg04-saline-base-signa-gel-8oz-tube-2-pack.html
No, the paste and saline pads are equivalent in conduction. So my suggestion is to just use the C3 C4 as before, with paste. Then on the ear clips, since they are spring loaded, all you need is the Shamwow saline pad between the skin and ear cup electrode. This also eliminates any fussing with the One-Wrap. Wish you had mentioned this before.
As we mentioned before, 'supersaturated' is not necessary. You can see the mixing instructions for the solution I use, on my saline page (previous link). It uses KCl instead of NaCl, but NaCl is fine. Don't use "sea salt", just plain salt. The proportions are the same as those used by the EGI Geodesic Sensors mesh caps. You can skip the anti-bacterial.
Thank you so much William! This is such great information. We are really happy to hear about the One Wrap way to set things up -- it might be good in the long run to find a saline set-up for the head as well in case there are more allergic reactions, as my mom is hyper sensitive. But it's awesome to know this is a good way to start.
Ah, great to know!! I will look at your saline page for the mixing solutions. This is just wonderful. Thank you so very much.
Hi again William--
Checking out your saline solution recipe -- I see that you use Dawn dishwashing liquid and Biguanide in the saline solution.
I guess the Biguanide is the anti-bacterial.
What about the Dawn dishwashing liquid? What does that provide to the solution?
A very very tiny amount of soap / detergent is recommended by the EGI Geodesic Sensor Net formula, to act as a skin oil dispersant. This aids in the skin conductance to the electrode. Dawn is particularly gentle and is actually used in animal rescue operations to help disperse any oil spills that seabirds come in contact with.
"Why Dawn Is The Bird Cleaner Of Choice In Oil Spills"
https://www.npr.org/templates/story/story.php?storyId=127999735#:~:text=When asked whether they have,like walking commercials for Dawn.
Fascinating!! Thank you.