If you watch the oscilloscope, you’ll get comfortable reading what EEG activity looks like: it is not generally repetitive or overly consistent. When all the wave forms are roughly the same height, instead of taller and shorter, that’s probably not brain. If the width of the waves are very consistent rather than shifting to wider (slower) and narrower (faster) patterns, again, that’s probably something mechanical rather than organic. Sudden spikes, especially when they are repetitive, probably also indicate a problem.

Artifact in Assessments

Artifacting can make a big difference when the artifact is strong. Watching for artifact when you replay a session, you can get a pretty clear picture of what it looks like on the Power Spectrum and/or Oscilloscope displays. Then you can recognize it on the screen during the assessment data gathering. That’s the ideal time. The more you can avoid artifact in the recording, the easier it is to remove it in the processing. You’ll end up with more seconds of clean data and spend less time getting it.

Do not assume that auto artifacting will “skim off” the high amplitudes. In a well-recorded assessment, the auto-artifacting frequently removes zero segments as artifact.

About my 2nd year of working with clients, Joel Lubar was kind of a mentor to me. He had come to visit us in Atlanta one time, and we had just gotten an artifacting version of what was called A620 software. You looked at two-second epochs as raw waveforms and either approved or rejected them based on the one channel of data. I had just gotten the software and begun working with it, so I was artifacting a file while Joel sat beside me at the computer. Joel was not one to suffer in silence, so after a few sighs watching me stare and stare at a 2-second epoch, he stood up to go out and get something from the car or something like that. As he left, he turned back to me at said, “try something for me.” He asked me to continue artifacting this 2 minute file as carefully as I possibly could and save the results. Then do it again as fast as I could, just removing the most obvious artifacts. “See how different they are,” he said and left for about 20 minutes. By the time he got back, I had gotten the message. Big, obvious artifacts are the ones that really mess up the averages and standard deviations of the data. The ones so small that you can’t really be sure they are or aren’t make almost no difference at all.

Eye Artifact

An eyeblink lasts 1-2 seconds in its effect on the EEG unless you are blinking very rapidly. Eye movement, cable movement and eyeblinks are all slowwave excursions, so they will appear in the power spectrum and oscilloscope.

Teach your clients to “peek through their eyelashes” when training frontally. I tell them, “pretend you’re in a room full of adults and you REALLY want to stay to see what’s going on, but you know they’ll make you leave if they think you are awake. So you pretend your eyes are closed, but you open them just enough to be able to see.”

Each eye has a voltage drop in the eyeball. Even being close to the eyes can cause an effect on the signal.

Eyes moving, even with eyes closed, will cause delta artifact the further forward the electrodes are.

You can and do blink and move your eyes when they are closed. Try it and you’ll see the effect on readings taken in the frontal areas. Regularity of the surges would suggest blinks.

I look at the power spectrum in bins mode. If all the frequencies on both sides surge out and then come back pretty much together, that’s almost certainly eye artifact. If the high amplitude activity appears in various frequencies and moves around in a more organic way, then it’s probably brain.

If you are consistently seeing high levels of delta (recognizing that delta is often the highest power in many brains except for posterior eyes closed alpha), I would always check the eyes. Eye movement, electrode movement, eyeblinks and even the eyes themselves can produce high levels of delta. And, of course, if you did not artifact the data before dumping it into the assessment, it’s pretty worthless. I work with dozens of trainers at any given point in time–include rookie home trainers just starting out–and see nearly all of them able to get useful assessments if the data are carefully gathered and properly artifacted.

Eye rolls also create artifact that appears as excessive slow activity. You can see them as the whole wave form rolls up off the baseline and then down below it.

Contact lenses tend to magnify blink artifact significantly.

Muscle Artifact

Any muscle tensing or bracing produces a surge in most frequencies, but especially in the higher bands (like high-beta). EMG is usually seen between 50 and 200 Hz, but, depending on the amplifier being used, the EMG may not appear at all, because the amplifier only reads up to 35-45 Hz. Nevertheless, high-beta (and often fastwave coherence as well) will appear very high when it is in fact an artifact of EMG.

EMG is usually defined as 20-200 Hz, though obviously there are lots of EEG signals in that range as well. If you grit your teeth while recording EEG, you’ll see a surge in nearly all frequencies, but the higher the frequency the greater the artifact. Since most amplifiers have lowpass filters built into them to cut off very high frequencies like this, depending on what amp you are using, you may be thinking you are training a frequency your amplifier can’t even see.

Oz is generally about 1.5 inches above the inion. That’s still pretty close to the neck muscles. Be very careful to have the client sit with head up, not dropped forward, to avoid producing muscle artifact from those muscles. This is an issue we talk about in the assessment process, especially for the Midline reading and especially at task.

Artifact in the Signal

Lots more 60 Hz signal when it is by itself is often a measure of quality of hookup. When it is very high relative to the rest of the power spectrum, it’s almost always an issue of poor impedances/bad scalp connections.

If levels of 60 Hz are within the range of the other amplitudes in the EEG and you don’t have impedance problems, it’s not a big thing. Remember that we don’t actually measure anything anywhere near there with the filters in the assessment or training designs. What you need to watch for is usually clear in the power spectrum. If you see regular spikes up and down the EEG (for example, at 22, 35, and 50 Hz), that is a seriously bad signal.

Heartbeat Artifact

Regular pulses, depending on their frequency, can often be related to artifact, especially ECG. Especially with clients who are heavy. You may be picking up pulsing in a blood vessel. It’s not common to see any kind of regular oscillation that affects all frequencies repeatedly. And since such an artifact would be expected to result in activity at all sites coming from the same source (the artifact), that would be a rule-out in a case where coherences were generally high.

If someone is producing ECG artifact, you can see the regular pulsing in the oscilloscope. Usually earlobes are a major culprit, so I move from the ears to mastoids or use a bipolar montage. Occasionally I have managed to get a head lead directly over a blood vessel under the scalp and moving the offending electrode will fix the problem.

I don’t recall having personally run into a client where we couldn’t get away from the pulse. I’d be hesitant to try to set up a filter in the specific frequency where the pulse occurs to filter it out, but that’s possible. Heart rates usually run from, say, 50-90 pulses per minute, which would be from around 0.8 to 1.5 Hz. (If your heart rate is 60 bpm, that would be 1 Hz–60 in a minute divided by 60 seconds.) Putting a filter down there with a threshold that blocks sudden amplitude surges would at least block the signal at those times.

You can actually move ear clips up to the cartilage area closer to the top of the ears. The problem with ECG is almost always in the earlobes, and moving to the mastoid or the cartilage almost always helps.

Electro-magnetic Fields

These can be caused by ungrounded laptops, power supplies, or almost any electrical equipment–sometimes equipment you can’t even identify. These often appear as high coherences in faster frequencies and high levels of fast activity.

Ungrounded laptops are a significant source of artifact. If you are using a 2-prong plug instead of a three-prong plug, even in a grounded outlet, you won’t get the benefit of the grounding, and you are likely to have a noisy signal. Try unplugging the AC adaptor from the wall and the computer while you are running and see if the signal cleans up.

Watch for coherence levels being artificially high if you have significant electromagnetic field interference. Even if you use your notch filter and keep the training range to 1-40, coherences can be adversely affected.

Electrodes that are scratched, have nicked wires or are long and stretched out creating an antenna to pick up signals also are a source of artifact.

I’ve certainly seen cases of intrusive EMF: in Zurich I did a workshop with one of their electric trolley lines outside the building and we all (using cabled amplifiers) had such horrible noise problems that we had to drop the part of the workshop related to gathering assessments. In Sao Paulo, trainers I consult with have struggled with such problems due to their proximity to a broadcasting tower. In California I was called to an office to figure out why it was impossible to get a decent signal in one room, when signals were fine on both sides and downstairs from the same office. None of us three “experts” who were there were able to find the source of the problem. All of those cases involved cabled amps. But those were very rare experiences among the thousands of situations I’ve seen and trained in.

Assessing and Training the Pre-Frontal Cortex

Fp1 and Fp2 are extremely difficult sites to evaluate and to train, because they are extremely close to the eye muscles (blink or eye movement cause excessive slow frequency artifact) and they are right over all those expressive muscles in the forehead. It is almost impossible, except with the most controlled and motivated client, to get a decent artifact-free reading there.