Testing in an EEG Lab — Trial and Error
Hi all, here’s an EEG update from Tegan.
So, I am lucky enough to have some previous experience in EEG (used to red real-time brain activity) before I started this internship. As such, the PhD candidate I’ve been paired with decided to hand the reigns over to me on my first testing day.
Let’s just say it didn’t go according to plan.
But first a disclaimer — I would like to say that I genuinely enjoy testing. Being relatively new at setting up an EEG experiment, it takes me about 30 minutes. So I get a lot of time to talk to participants. I have met a lot of different people so far, which I really enjoy. One of my first participants was an exchange student from Ireland. And since Ireland is my #1 travel destination, I was very excited to learn all about it. Do you guys get much time to talk to participants?
However, getting back to the process. Set up can kind of be described like a beauty regime — I need exfoliant, gel (a lot of it), a q-tip, a cotton pad, a cap, a blunt syringe, and a lot of patience. And the electrodes (which don’t really fit my beauty metaphor, oops).
There’s a suprising amount of skin prep. I first need to exfoliate and wipe clean the areas of the face I test on. After that, I can put on some face electrodes using gel. The most important ones are the nose and the areas behind the ears. That’s because these are the electrodes that you reference from. Which basically means that they the help evaluate the data from all the other electrodes.
A side-note: the first time I set up an EEG on my own, I forgot to put gel on the electrodes. Which meant I had to go back and re-do all of it again. A pain. The gel is really important because it enhances the ability of the electrodes to pick up electrical activity. Without it, I wouldn’t have gotten much data.
After I finish with the face electrodes, I can put on the EEG cap. Which looks like a cotton swimming cap with a bunch of holes in it. There’s 64 holes, to be exact. Putting gel in each of them and then plugging them with the matching 64 electrodes takes up most of the set up time.
The problem with gel is that you have to get the amount right. If you don’t put enough in, then the electrodes pick up poor signals. If you put too much in, then the EEG machine basically flat-lines (we call it “bridging”). This means that you have to write off that participant and try again with the next one. It’s a very stressful balancing act.
And, unfortunately, on my first testing day I bridged. It’s a humbling experience, I must say, having to explain to a participant that I’m new at EEG and didn’t get it right.
Alas! This story has a happy ending. The thing with bridging is, is it’s really hard to tell the difference between putting too much gel in and having a broken electrode. So, when the PhD student also kept “bridging” his experiments, we thought something might be wrong — and not with us.
The thing I really love about this lab, is that everyone is so supportive. We didn’t have to look around too much before one of the professors was willing to spare 15 minutes to check it out. So, I became the participant and we waited for the EEG to bridge — which it did [success!]. And it took the professor all of 5 minutes to diagnose that it was one of the face electrodes that were broken.
Conclusion: the PhD student and I don’t actually have terrible EEG skills. It was just a broken electrode.
Overall, I really do enjoy testing. Using EEG can be a test (ha) of patience, but seeing your data come to life on the screen never ceases to amaze me. The beautiful thing about EEG is that you can see the real-time brain activity of your participant. And even though this is illegible without data analysis and processing, it’s still really cool and absolutely worth it. How are you guys going with testing?
Thanks for tuning in on my disaster,
Tegan.
