What is Brainwave Rhythms

What is Brainwave(EEG)?

Brainwaves, also known as EEG (Electroencephalography), are produced by synchronized electrical pulses from masses of neurons communicating with each other. These subtle signals are detected by the sensors placed on your forehead on the inner side of the Flowtime headband. Flowtime collects the data and extracts the valid signals to make the real-time brainwave that reflects the change of brain states.
 
Real-time Brainwave (EEG)
After you put on the headband, it takes some time to finish calibration (if the skin is dry, it may take longer, about 30s to 1 min). During this time, you may also see the real-time brainwaves, but not stable due to too much noise. After that, you'll see the consistent real-time brainwaves.
For a better experience, a small amount of Electrooculography (EOG) is included in the brainwave data, so you will see real-time brainwave changes accordingly when you blink, move your eyes, or have other facial movements. But too many facial movements like grinding your teeth will make too much noise for brainwave analysis, which will result in a flat line of the real-time brainwave.

What is Brainwave Rhythms?

The brainwaves are divided into five kinds of rhythms based on their frequencies. They are α wave, β wave, θ wave, δ wave, and γ wave. When your brain is in different states, the percentage changes. Through frequency domain analysis of real-time brainwaves, we'll know the power ratio of each brainwave. The change in their percentage reflects the change of brain states.

There are slight discrepancies in the frequency bands of the brainwave rhythm reported on different papers. The frequency band adopted in our algorithm is based on below. [1]

 Besides, the ratio varies from person to person, related to gender and age, etc. [2][3][4]


Following is a typical case from a young man at the age of 28 when he was awake with his eyes open: β waves are dominant (30%-40%), θ waves the second (25-35%), α waves the third (20%-30%), γ waves the fourth (around 10%) and δ waves the last (below 10%).

The ratio may be different from the result made through the clinic or other devices as the data profoundly depends on the device's sensitivity to the frequency and the sensor placement.

How to understand Brainwave Rhythms graph?


The change of brainwave energy reflects the change of mental state during meditation.

 

A user's report of Brainwave Rhythms after meditation

 

Absolute Brainwave Rhythm (dB) in a typical meditation state

(As a 3-year meditator, his alpha and gamma wave energy showed an increasing trend as he entered the meditation state.)

 

Absolute Brainwave Rhythm (dB) in certain meditation states

(The user has many years of meditation experience, and he shifted ways of practice as two distinctly different states emerged in which beta and gamma wave energy rose significantly.)
 
Tips: The value of the y-axis is dB, but the scale is not fixed. It's made based on the highest and lowest value of each session.

References

1. Sanei, Saeid & Chambers, Jonathon. (2007). EEG signal processing. 10.1002/9780470511923.
2. Doppelmayr, Michael. (2004). Changes in EEG-bandpower and coherence in the theta, alpha, and gamma band while solving Raven's Matrices. International Journal of Psychophysiology. 54. 38-38.
3. Otero GA, Pliego-Rivero FB, Fernández T, Ricardo J (2003) EEG development in children with sociocultural disadvantages: a follow-up study. Clin Neurophysiol 114:1918–1925.
4. Latta F, Leproult R, Tasali E, Hofmann E, Van Cauter E (2005) Sex differences in delta and alpha EEG activities in healthy older adults. Sleep 28:1525–1534.
September 06, 2022 — Flowtime Team
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