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EEG Assessment of Brain Function

Can EEG (electroencephalogram, or brain waves) give a useful assessment of brain performance? By useful I mean one which would point to ways of improving brain performance, and more specifically suggesting one method as being more likely to help than another. In this article I'm going to make the case for a 'yes' answer, and show how EEG assessment can be useful.

An EEG assessment is an obvious starting point for a course of EEG neurofeedback, but I think its utility goes beyond that, to include (peripheral) biofeedback, and other forms of neurotherapy (e.g. brain stimulation, also HEG neurofeedback) and perhaps even nutrition and other forms of brain biohacking.

Medical & Psychiatric Diagnosis

First let me say that the sort of EEG assessment I'm going to be talking about here is not used to make medical diagnoses, i.e. for disorders such as clinical depression, OCD (obsessive-compulsive disorder), ADHD (attention deficit hyperactivity disorder) and chronic fatigue syndrome (CFS). (That said, an EEG based system has been approved by the US FDA as a diagnostic tool for ADHD). It's also worth adding that only medical doctors can make diagoses (not the likes of me).

Everyday Stress Problems

But what about everyday issues such as stress, anxiety, brain fog, fatigue and low mood? I think EEG assessment can give very useful information about the forms that these problems can take, and suggest ways to work with them. To explain how, I need to describe what EEG actually is.

What Is EEG?

Electroencephalography (EEG) is simply the measurement of small voltages from the scalp. These voltages are oscillating in a complex way - particular patterns of oscillation are known colloquially as brain waves - I'll return to these shortly. The oscillations derive from populations in the outer cortex of the brain, acting in concert.

This simple definition belies the true nature of EEG, which is that it's an extremely complex phenomenon that contains an enormous amount of information. What makes it so complex?

  • The complex nature of the wave forms - EEG typically is not just one simple rhythm but a whole set of oscillations mixed together.
  • The EEG varies across the scalp. An EEG assessment compares different parts of the brain (e.g. left to right, front to back) an indeed this is some of the most useful information. There are computational measures in the EEG (e.g. coherence) that indicate how well connected different brain regions are, how well they are communicating. The most advanced EEG assessments tools record from hundreds of points on the scalp at once.
  • Whilst the physiological origin of the EEG is quite well understood, relating EEG informations to high level brain functions such as attention, motivation and emotions is far from straight-forward. The patterns that I'll talk about below are general tendencies, not fool-proof measures. It's easy to over-interpret the EEG. In some ways interpretting EEG is like analysing an engine by listening to the sounds it produces.

EEG Rhythms or Brainwaves

Again, the raw EEG is a voltage, varying in a complex way, such as this:

eeg or brain waves - raw

Sometimes, in some parts of the head, the EEG shows a clear rhythm such as this:

alpha rhythm in EEG

A rhythm can be described in terms of (i) frequency - how many cycles per second and (ii) amplitude - size of the voltage or height of the waveform. In the second graphic above you can see that the frequency, or the relative spacing of the peaks, is relatively constant, while the amplitude varies.

EEG frequency varies between around 1 and 40 Hertz or cycles per second. Different bands within this range have been given names, for example 8 to 12 Hz is alpha - the above rhythm is an example of alpha. Others are delta, theta, beta and gamma.

A complex EEG can be considered as a mix of different component frequencies - so much alpha, and so much beta, etc, varying over time.

Computers can analyse EEG into these component frequencies, in different ways. I'm not going to go into any details, but the result is often called a frequency spectrum, or spectral analysis. An example is shown below. One thing to bear in mind is that the calculation is always based on a window of time - it might be three seconds or three minutes or three hours. Obviously 3 secs is a snap shot of brain function, while 3 hours and even 3 mins is a more averaged picture (which for the most part is more useful).

EEG frequency spectrum

In the above graphic you can see that the "alpha 1" frequency component is high - meaning the brain is generating an alpha rhythm.

Brain Waves and Mental States

To an extent, the EEG frequency components or brain waves correspond to the brain functioning in certain ways, or in other words they (loosely) correlate to states of mind.

What do the different frequency bands mean? I've described the major bands below, but remember the correlations are loose etc ....

  • Delta - 1-4 Hz
  • Delta is most commonly seen in deep sleep, and also in certain types of brain damage. It seems that sections of the cortex generate delta when they are off-line, or disconnected from the rest of the brain. That said, there's always some delta in the EEG.
  • It's interesting to note that delta tends to increase when you hold a mobile phone to your head for some minutes.
  • Theta - 5-8 Hz
  • Theta is associated with a dream-like, intuitive or creative style of brain processing. You tend to see theta more prominently in the back of the head as you drift towards sleep (the hypnagogic state).
  • There's also something called "frontal midline theta" which is quite different. It's linked to memory processing.
  • Alpha - 8-12 Hz
  • The brain generates alpha when it's "ready and waiting" - it's a kind of idling rhythm. Alpha is associated with relaxed alertness. It's seen more prominently in the back of the head, especially when the eyes are closed (when the visual processing areas at the back of the head don't have anything to do).
  • In fact alpha can jump up by as much as 300% or more just by closing your eyes. Do you really feel so different when you close your eyes? This is a reminder not to over-interpret the EEG. That said, some people don't show this change, and they tend to have certain problems (more on this below).
  • Beta - 13-30 Hz
  • The brain shows predominantly more beta when it's engaged in cognitive processing (in broad terms, "thinking" - but focused, not daydreaming). At such times the brain suppresses the lower frequencies (delta, theta, alpha). If your brain struggles with this slow-wave suppression, you'll probably be somewhat cognitively impaired.
  • Gamma - 30+ Hz
  • Gamma is sometimes known as fast beta. Perhaps the thing that gamma is most famous for, is that brains seem to display synchronised gamma across the whole scalp, in a state of clear intense awareness (e.g. this kind of gamma has been seen more prominently in experienced meditators).

EEG Assessment, Brain Performance & Stress

What useful information can we get from the EEG from the point of view of working with problems like stress, anxiety, brain fog, low mood and fatigue, or more generally improving brain functioning?

First let me tell you about two approaches to answering this question.

Normative Databases

One approach is to build up a database of EEG brain maps of lots of "normal" or "healthy" people. Then to assess any individual, you compare their brain map to the average scores of these "normal" people, and see where it differs. Or you could study a group of people with say OCD or some other disorder, and see how their brains typically differ from the norm.

This approach has been used, especially in the academic world. It's the basis of QEEG guided neurofeedback.

The main problems with the normative database approach are:

  • There's such a wide range of "normal", that the resulting databases aren't sensitive enough to highlight minor everyday problems. "Healthy" typically just means not having a medical condition.
  • We aren't aiming for an average brain but an optimally functioning one.

Imagine taking the same approach for weight - the average weight of people who don't have a medical condition is not the same as an optimal weight.

Symptoms Based Approach

Another approach is to start with a population of people seeking help for brain related problems, collect information about their symptoms, then measure their EEGs, and look for correlations between symptom severity and particular EEG parameters such as alpha amplitude.

This was the approach taken by Dr Paul Swingle, one of the world's leading neurofeedback practitioners. Dr Swingle developed a system of assessment that avoids the problems mentioned above, and in addition has the advantage of being quick and easy - it involves recording from just five sites on the scalp (typically for just a couple of minutes or so) and can be performed with inexpensive equipment. It's not suitable for complex brain problems, e.g. autism.

Dr Swingle's system is called the "Clinical Q". Other systems similar to it are available, including the one I use in my own practice - I do stress that it is not the same, and it is not approved or endorsed in any way by Dr Swingle.

EEG Markers for Non-optimal Brain Functioning

What EEG parameters do systems like Dr Swingle's measure, and what do they signify?

Frequency band amplitudes (alpha, theta, beta, etc.). In fact absolute amplitudes aren't as useful as relative (e.g. theta in relation to alpha and beta) partly because of individual factors such as skill thickness, but also because there are variations between devices.

Frequency band ratios are therefore more significant. I'll mention just a couple of them.

Theta : Beta

This is probably the best established of the simple EEG measures. When it's too high at the front of the head, it tends to predict brain fog and poor focus and concentration. (In fact the FDA approved system I mentioned earlier is based on theta:beta).

At the back of the head, theta:beta is generally lower - but if it goes too low it predicts agitation, racing thoughts, mental busy-ness and an inability to switch off - in other words the most common form of stress. Some cases of anxiety look like this. In my experience (i.e. in my client population) this marker is the most likely to show a problem.

High Beta : Beta

This ratio, when measured right on the midline of the head towards the front, can indicate obsessiveness and rigidity (lack of mental flexibility) when it creeps too high. A little above average can indicate a healthy persistence or even stubbornness. If it's too low it suggests passivity.

More EEG Markers

Alpha Response

I mentioned earlier that alpha at the back of the head should jump up when you close your eyes. If it doesn't (i.e. you don't show an alpha response) the most common explanation given is psychological "trauma" - not necessarily extreme trauma, hence the inverted commas.

The graphic below shows alpha amplitude recorded from the back of the head over a couple of minutes. The subject closed their eyes between the two dotted lines - you can clearly see that alpha jumps up substantially, so this is a healthy alpha response. Sometimes the alpha response is slow (delayed) suggesting it's inefficient in some way.

alpha response in EEG

Alpha Speed

The peak frequency within the alpha band, known as dominant frequency, is a kind of brain efficiency marker - the higher the better. Research shows alpha dominant frequency correlates with intelligence, and it's known to fall with age, markedly so in cases of dementia (e.g. Alzheimer's). Ideally the peak alpha frequency should be above 10 Hz.

Left-Right Brain EEG Patterns

There is a very well established research finding that the left frontal region of the brain is a little more active than the right, in emotionally healthy people - but it people with depression or low mood this pattern can be reversed. In terms of EEG, ideally there should be a little more beta on the left, and a little less alpha, compared to the right side.

Sometimes left-right imbalances manifest as emotional volatility (instability), or tendency to anger and rage.

Front-Back EEG Patterns

In a similar way, in a well-functioning brain you expect to see significantly more alpha at the back of the head than at the front, and the opposite pattern predicts brain fog. In beta, there's ideally slightly more at the front of the head (the front of the brain is called the Prefrontal Cortex and it's known to be the seat of executive function - including focus and attention, planning and organisation, also emotional regulation).

Boosting Brain Performance

An EEG assessment is always interesting, but it's real value is in suggesting methods for improving brain performance. Once again I stress that because of the heuristic nature of EEG markers these are no more than suggestions - they aren't guaranteed to work.

Here I'll give some examples of how specific EEG assessment findings can suggest particular courses of action, that make sense at least theoretically. I'll mention a couple of techniques of brain stimulation:

  • AVS or Audio-Visual Stimulation - "light and sound" machines generate visual flashes at particular frequencies, and also audio beats, and work by entraining the brain - which means that the brain's EEG falls into step with the rhythm generated by the machine. Obviously the frequency the machine generates is key.
  • tDCS or Trans-cranial Direct Current Stimulation - in this technique a constant voltage is applied to the head. It's probably best regarded as an experimental method, but it's generating a lot of interest because the (small scale) research shows it helps e.g. depression, and low cost consumer devices are available. In some way it activates the part of the brain under the electrode.

Here are my examples:

1. Low theta:beta at the back of the head - again, a marker of a busy agitated mind that won't swith off.
  • Peripheral biofeedback - I personally favour Optimal Breathing Training with Biofeedback - my favourite stress management technique.
  • Alpha-theta neurofeedback
  • AVS, using a frequency in the alpha or theta range.
2. Left-right imbalance - emotional problems
  • tDCS, using a left-right placement of the electrodes - so that you "activate" the left front brain, which again is associated with emotional positivity. This protocol has been shown to help depression.
  • AVS - certain devices can send different frequencies to each half of the brain. To improve mood you'd probably want to "activate" the left brain using something like a beta frequency, and "calm" the right brain using something like an alpha frequency.
3. Front-back imbalance - brain fog
  • HEG neurofeedback - this is a form of neurofeedback based on detection of metabolic changes in the brain (i.e. changes in metabolic activation or energy consumption). Typically the sensor is placed on the forehead - it's a simple way to train the executive brain.
  • tDCS - this time using a front-back placement of the electrodes so that you activate the front of the head.
4. High frontal theta:beta - brain fog and ADHD
  • HEG neurofeedback again
  • Consider nutrition - although I haven't seen evidence for nutritional interventions, some studies have shown that certain drugs can lower theta:beta, suggesting this marker might indicate a problem that is more biochemical in nature.

Resources & Further Reading

For more information on Dr Swingle's assessment, I recommend his books, especially "Biofeedback for the Brain" which is aimed at a lay audience.

The EEG assessment I use in my own practice uses software I developed myself - it's available for sale and you can read more about my EEG assessment here. Please note my software is not approved or endorsed by Dr Swingle.

Here is an EEG assessment sample report.

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