Nineteen-Point EEG and Evoked Potentials Tests

Published Categorised as Brain Power, Personal, Brain Health

I went for another 19-point EEG assessment at the ADD Centre this past week. I’ve had, I think, three of these before, the last one being in September 2007. Things have changed!

First off, much better cap. It’s stretchy and easily goes over all my hair. Plus the electrodes are on the outside. The syringe that injects the electrically conductive gel is still as pointy as ever though. Second, the testing was quite a bit different. I had two EEG tests: the first was on the older equipment so that it could be compared to my previous tests; the second was on wireless, highly sensitive equipment that is connected instantly to Evoke Neuroscience in the US so that they see my brainwaves at the same time as we do. Way cool.

For Test One, there was one laptop and a large box, the size of a fat hardcover, where the EEG and ECG leads are plugged into. For Test Two, there was a monitor in front of me, a small laptop to my right, and a palm-sized wireless box that the leads were plugged into. Big change in box tech, eh!

Test One

The impedance test is done with the new software because they use the same cap and electrodes for both tests, and the new equipment requires a better impedance. Impedance here is a measure of how well the electrodes are reading the brainwaves, that is, how well the electrical waves are getting through to the electrodes. It took awhile to achieve good connections. The last time I had the EEG done, it took eight minutes to get good impedance; the first time twenty minutes. This time, it was like my first time.

The stretchy cap on my head has nineteen electrodes on it corresponding to specific pre-mapped points on my head. After putting that on me, Andrea strapped three white electrodes on my upper left forearm and both wrists to measure my electrocardiogram (ECG). She squirted gel into each (that gel stays liquid till you take the electrodes off, wipe all the gel off, and then it turns into a dry film, ack!). Andrea began by pasting and clipping the ear electrodes on. Your ears are the grounding wires, so to speak. Then with a syringe, she squirted gel into each of the nineteen points and began to use the pointed end of the syringe to create a gel connection between my scalp and the electrodes. Dr. Michael Thompson brought up the impedance screen on the monitor in front of me to show her progress – each circle changes from green to black as connection is achieved. It’s a line drawing of a head with two ears and the nose from the top view. There are twenty-one circles on it, two on the ears, the rest on the head.

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Andrea changed all the circles on the screen from green to black. While she was doing that, I answered a few questions on a paper questionnaire about my memory and concentration. Then I moved myself and some wires, and most of the black went green again. Poor Andrea (and my scalp), she had to work on it again. After a while, she decided it was just random flickering from black to green to black, and we began the test.

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First, I sat with my eyes closed for, I think, five minutes while Dr. Michael Thompson recorded my brainwaves and ECG on the laptop. ECG popped up first, then EEG. Once the waves were showing fully on the screen, I had to reduce muscle tension by actively relaxing my jaw and shoulders. It is very hard to sit still with eyes closed, keeping one’s jaw totally relaxed.

When eyes closed EEG/ECG test was done, we talked about memory. The staff at the ADD Centre will do this sometimes between tests or biofeedback sessions as a way to relax you or give you a break, or sometimes to work another part of your brain. Also, for me, it’s interesting to talk about brain stuff with him.

Then he had me sit and stare at one of the lead wires as it hung down the outside of the box for five minutes for the eyes open EEG/ECG reading. That way, my eyes are open but downcast and are looking at something that won’t allow me to be distracted. Of course, what I hear is still distracting. The room is pretty quiet during these tests though.

Test Two

After that five minutes was up, Andrea took off the strapped-on ECG electrodes, and she unplugged the EEG leads from the big box and plugged them into the palm-sized wireless box. She stuck an ECG electrode onto the base of my neck on the left side. Then we watched the EEG/ECG readings on the monitor in front of me to make sure all was kosher. I must say I found it hard to follow the readings because they didn’t scan across the full width of the frame before they disappeared and began rescanning again. And they scanned very, very quickly. We watched for awhile. This particular technology is still in its Beta phase, I understand. But aside from that, the rest of this test was easy to follow.

This test has four parts to it. The first part is a questionnaire. Then like Test One, there’s five minutes of eyes open then five minutes eyes closed. The last part I’ll explain in a moment.

For part one, the BrainCheck Screener by Evoke Neuroscience, I was given a mouse and the computer showed the questions on the monitor in front of me. Each question had multiple answers. As I clicked each answer, the computer moved through the questions. The eyes open and closed recordings were in the opposite order from Test One. Since Dr. Thompson is big on being relaxed, I think he has you start with eyes closed to ensure you begin as relaxed as possible. The chair one sits in is a big, cushy leather one that swivels and can lean back with a little effort. I wonder how many fall asleep? Dr. Thompson talks you through relaxing and only begins Test One once he sees the muscle tension drop to where he’s satisfied with it. In Test Two, the computer guides you.

When I was done, Andrea gave me a clicker that looks like a small black handheld microphone with a lit red button on top. I had to practice clicking that button, maybe because I still have weakness in my right hand.

The last part tests your evoke potentials. The way I understand it is that when you receive a stimulus, your nerves and neurons respond before you are conscious of seeing the stimulus. That response is standard in you and cannot be altered by your conscious control (though can be through injury, for example); whereas when you see something, you can choose whether or not to react to it. So an evoked potential is a way to evoke or stimulate that subconscious physiological nerve response, which the computer records. The reason why the new equipment has to be so sensitive to EEG amplitudes is that these evoked potentials are small in size.

The ten-minute test comprises three images flashed very briefly in seemingly random order against a white background on the monitor interspersed with a burst of sound through earplugs. You have to practice distinguishing between the first two images, which are a small blue circle and a large blue circle because they are not that different in size. I got 80% in my first practice and so could go on to the test immediately. I found that as the test went on, the large circle began to look huge to my eyes. We had to also test that the volume of the auditory stimulus – a burst of scratchy white noise – was not too low. Well, I have really sensitive hearing. Normal volume made me almost hit the ceiling. After a couple of tries we got the volume down enough so that it startled me but didn’t make me physically jump (well, not too much). I was also shown the visual startle stimulus, a black-and-white checkerboard pattern that filled the screen. Now familiar with what I would see and hear and knowing I was to click only when I saw the large blue circle, I began the test. The computer conducts the test.

At the end of the ten minutes, I was done, exhausted, and divested of all electrodes. Even though Andrea wipes off all the gel, I still looked like Ms Frankenstein, but at least not as bad as after a sleep study. There they use paste. Paste is like concrete; the gel like mortar.

The final part was a one-hour online neuropsychological test I did at home in a quiet place. I had a choice of doing it at the ADD Centre or at home, but after spending a lot of time discussing some of the results of Test One that Dr. Thompson had already compiled while I did Test Two, I had to leave. I was starving, and lunchtime had gone and suppertime was nearing.

I now await the full results of the two tests.

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