The activity happening within the brain is electrochemical by its nature. When this activity is measured, it can be broken down into five major frequency bands: delta, theta, alpha, beta and gamma. Roughly speaking, these bands correspond to certain biological states.

For example, delta waves are prominent in slow wave sleep (SWS, stage 4 of NREM). Beta waves are seen in normal waking state as well as intense thinking or concentration. Theta waves are seen with meditation, hypnosis, trances and other altered states of consciousness.

In other words, with a suitable measuring device, it is possible to get objective feedback about what your state of consciousness is.

What causes these wave-fluctuations? Electricity; remember that the activity happening within the brain is electrochemical. There are minute electrical fields involved.

To measure such fields, for example an EEG (electroencephalography) device can be used. The procedure for noninvasive EEG works in principle like this: electrodes are placed on the scalp, possibly at multiple positions (the channel count of EEG devices refers to the number of such positions). For invasive EEG the electrodes are inserted directly into the brain, which is obviously something a home experimenter will not want to do, unless they wish to win the Darwin Awards. After electrodes are in place, the tiny electrical signals are sensed and amplified by the device and filtered suitably for analysis.

Below is a table illustrating the states related to the five major frequency bands: delta, theta, alpha, beta and gamma:

Delta < 3 Hz Babies, deep dreamless sleep, SWS/stage 4 of NREM
Theta 4 .. 7 Hz Young children, drowsiness, other altered states of consciousness in older individuals
Alpha 8 .. 12 Hz Closed eyes, relaxation.
Beta 12 .. 30 Hz Active thinking and concentration
Gamma 20 .. 100 Hz Not measurable with EEG due to attenuation from skull and scalp

Experimenting with EEG and Brainwave Measurements

To experiment with brainwave measurements, you would first have to obtain a device capable of measuring such activity. Clinical-quality EEG devices with many measurement channels can be expensive and hard to attain, let alone operate for a non-medical professional. Some EEG devices for consumers are created, for example, by BrainMaster, Guger Technologies, Mind Media. Nowadays one can find also some consumer-grade brain-computer interfaces (meant for gaming purposes) which seem to have EEG features.

If you like to tinker with electronics, there is a project for creating a construction kit for an EEG device. There is also a commercial medically certified version of OpenEEG platform called MindMaster EEG, but it is very expensive and unfortunately only available to residents within Germany and Austria.

Note, that even a few EEG measuring channels is enough for non-clinical applications and private exploration.

Uses of EEG and Brainwave Measurements

Through brainwave measurements, you get information about the “current state” of your brain’s activity. This information can be used for biofeedback applications (also known as neurofeedback in this context). For example, if you want to learn how to efficiently make yourself relax, you can observe the changes in brainwave activity and try to focus more on the things (e.g. a relaxing memory, kittens, a sunny beach) which seem to bring the brainwaves towards the lower bands.

What if You Have No EEG Device?

Obviously, if you are drowsy enough, you will notice it indirectly, e.g. by bumping into furniture when walking around, or through problems focusing the eyes. I’ve noticed it myself that when doing Ganzfeld experiments in the evening (when I’m already slightly tired), I can spot the onset of sleep from the way the eyes just stop focusing, begin to “roll around” when attempting to focus, and can be opened at most halfway open. It’s like trying to read a book when one is starting to fall asleep. However you notice the effect in yourself, it is an important observation to make and learn to detect, especially if you intend to do experiments with the hypnagogic state!