The Power of Brainwave Frequency: Interpreting Dominant Frequencies in Neurofeedback

Brains are like powerful operating systems, driving a person’s health, for better or for worse. Harnessing the brain’s power and guiding it towards healthy functioning is the goal of neurofeedback training. Like a wild horse, the brain may need guidance to direct its power. Neurofeedback training acts as a bit in the horse’s mouth. It’s designed to help harness the brain’s power and lead it towards better health. Neurofeedback training does this by interacting with brainwave frequencies which make up a person’s brain state. In a way brain states reflect a person’s status or mode. They indicate whether a person is alert or asleep, anxious or calm, and more. In order to help clients harness the power of a dominant brainwave frequency, first, clinicians must learn how to interpret dominant frequency.

What is Dominant Frequency?

Gaining a solid understanding of dominant frequency is essential to the work of neurofeedback training. When dominant frequency is discussed, it’s important to clarify that the term dominant frequency refers to where the most power shows up, when comparing the different points along the frequency spectrum. Essentially, it means the frequency that has the most power. In other words, the dominant frequency is where the most amplitude can be seen, according to a frequency spectrum chart.

Identifying Dominant Frequency

It may be helpful to practice identifying dominant frequencies. The chart below shows the alpha component band. This view takes the frequency bands that make up alpha and shows the individual frequencies at 8, 9, 10, 11 and 12 Hz. The amplitude, which is measured in microvolts, can be  seen along the y-axis. So looking along the x-axis helps to answer the question: at which Hertz is the amplitude the highest?

To know the dominant frequency for alpha in this EEG, look at the highest bar in the chart and then ask: where, along the frequency spectrum, is the greatest amplitude? In the chart below, it can be seen that the dominant frequency is between 10.0 and 10.5 Hz. So, basically the dominant frequency shows at what frequency (Hz) is the most power. 

The first chart only shows the alpha bands and which is the dominant frequency. The next chart shows the bands for each type of brainwave. Frequency bands are given at 1 Hz in the next chart. The dominant frequency can be found for each band (color coded from left to right): delta, theta, alpha, low beta, beta and high beta. The dominant frequency for each band is listed below.

Dominant frequency for each band, according to 1 Hz chart

• • • • • Delta: 3 Hz
        • Theta: 4 Hz
        • Alpha: 10 Hz 
        • Low Beta: 15 Hz
        • Beta: 16 Hz
        • High Beta: 21 Hz

Notice that the dominant frequencies are reported in hertz. Since hertz refers to the cycles per second, it is said that a dominant frequency is “fast” or “slow” compared to a normal EEG. To say “high” or “low” when talking about dominant frequency is inaccurate.

Dominant Frequency and Brain States

Knowing what dominant frequency is and how to find it in a chart is great, but how does that relate to brain states? After all, influencing brain states is the goal of neurofeedback training. So how can dominant frequencies show a person’s brain state?

Brain states like sleep, awake, alert, high alert, anxious, focused or meditative, etc., all have their own indicators on EEG charts. For example, delta has a frequency range of 0.5 to 4 Hz. So if there is a dominant frequency at 4 Hz, then that’s the faster side of a delta range. This would show that the brain state is consistent with sleep. 

Since beta ranges in frequency from 12 to 40 Hz, then a beta dominant frequency at 35 Hz is on the fast side. This is considered beta dominance and it could indicate a brain state that is very alert or anxious.

Another way to tell whether or not a dominant frequency is normal for brain waves is by looking at the color coding in the brain maps. A dominant frequency in alpha is in the normal range (~9.5 to 10.5 Hz). The circles in the portion of the brain map labeled “alpha” are green which indicates that this dominant frequency is normal compared to a healthy EEG. 

Interpreting Brainwave Frequencies with Reference Ranges

Understanding how each of the brainwave frequencies are represented in a normal, healthy sample helps to identify when a brainwave may be a sign of an unhealthy brain state. In order to get a sense of which brainwave frequencies are fast or slow compared to normal, it is useful to look at the individual reference ranges for each type.

Once the dominant frequencies in a qEEG brain map are identified, then the next step is to use the reference ranges to see whether or not it is in a normal range. Any of the locations in the brainmap with dominant brainwave frequencies that are not in the normal range should be investigated. This can be done by comparing the patterns that are seen in disordered clients. From there, a clinician can get a better sense of how to help a client going forward. 

Using Dominant Frequency in Neurofeedback Training 

Understanding how to help a client means knowing what type of brainwave frequency training strategy to use. When it comes to applying the knowledge of dominant frequency, there are certain strategies that can be used. After interpreting whether or not a dominant brainwave frequency is within a normal range, a plan can be developed for intervention. The strategy may depend on what kind of pattern is seen in the EEG distributions of the brainwave frequencies.

For example, when alpha dominant frequency is abnormal other brainwave frequencies may be abnormal as well. Higher alpha amplitudes, occurring around 9.5 Hz, are usually associated with abnormal EEG distributions. Recognizing patterns like these is useful for determining which brainwave frequencies to train.

Training Specific Brainwave Frequencies

Once patterns in brainwave frequencies are assessed, it becomes a matter of deciding on the appropriate training strategy. While a training strategy like sensory motor rhythm (SMR) may be appropriate for a variety of conditions, there are other training methods that may be applied in a more specific manner. Here are some studies showing how certain neurofeedback training strategies may be applied.

Alpha asymmetry training in depression. When an EEG shows asymmetry in the frontal lobe, it could be a sign of depression. In this case, the individual displays left prefrontal alpha amplitude that is higher than the right. A training protocol that has shown results is aimed at increasing the activity in the right frontal lobe while at the same time decreasing it on the left. In the study, after 5 weeks of training sessions, participants in the training group showed a relative increase in right frontal alpha. This study suggests that training alpha brainwave frequencies, specifically increasing activity in the right frontal lobe may be effective in reducing symptoms of depression. This is referred to as an asymmetry protocol.

Reducing alpha in ADHD. Research suggests that observing brainwave frequencies in real time with EEG, may help in understanding ADHD. There is even a discussion of the possibility of alpha oscillations to be used as a biomarker. Using a training strategy aimed at reducing alpha, researchers observed an interesting post-neurofeedback effect in the ADHD group. These participants had an alpha rebound after their session, where previously abnormal alpha levels were normalized. During this post-session alpha rebound, they showed improvements in motor inhibition. 

Knowing how to interpret dominant brainwave frequency helps when choosing which training strategy is best for the client. Applying the appropriate training strategy has helped people find success towards their personal goals. Accurately interpreting qEEG brain maps and applying neurofeedback training can help clients harness the power of their brainwave frequencies.

Interpreting Dominant Brainwave Frequency Leads to Client Success

Knowing how to interpret brainwave frequency is pivotal to helping clients achieve results with neurofeedback training. It’s essential to building an effective strategy. When the right strategy is used, brainwave frequencies respond and brain states are adjusted. Guiding the brain towards specific brain states harnesses the power of the brain, according to the client’s goals. Whether the goal is to improve memory and attention or to calm an anxious mind, choosing the right strategy can be very empowering.

 

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Works Cited

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