Brain waves are generated by the building blocks of your brain — the individual cells called neurons. Neurons communicate with each other by electrical changes.We can actually see these electrical changes in the form of brain waves as shown in an EEG (electroencephalogram).
Brain waves are measured in cycles per second (Hertz; Hz is the short form). We also talk about the “frequency” of brain wave activity.
The lower the number of Hz, the slower the brain activity or the slower the frequency of the activity.
Researchers in the 1930’s and 40’s identified several different types of brain waves. Traditionally, these fall into 4 types:
– Delta waves (below 4 hz) occur during sleep
– Theta waves (4-7 hz) are associated with sleep, deep relaxation (like hypnotic relaxation), and visualization
– Alpha waves (8-13 hz) occur when we are relaxed and calm
– Beta waves (13-38 hz) occur when we are actively thinking, problem-solving, etc.
For obtaining basic brain patterns of individuals, subjects are instructed to close their eyes and relax. Brain patterns form wave shapes that are commonly sinusoidal. Usually, they are measured from peak to peak and normally range from 0.5 to 100 μV in amplitude, which is about 100 times lower than ECG signals. By means of Fourier transform power spectrum from the raw EEG signal is derived. In power spectrum contribution of sine waves with different frequencies are visible. Although the spectrum is continuous, ranging from 0 Hz up to one half of sampling frequency, the brain state of the individual may make certain frequencies more dominant.
We can see and measure these patterns of activity in the EEG.