By attaching electrodes to the scalp and using a device known as an electroencephalogram (EEG), we can view and analyze the traces of electrical activity in the brain that represent the “brain waves”.
Like all waves, brain waves have a frequency, measured in cycles per second or Hertz (abbreviated Hz), which is the number of cycles the wave goes through in one second. So, a lower Hertz number represents a slower wave.
Brain waves are categorized by their frequency. There are four kinds brain waves generally known to science and measured by EEGs – alpha, beta, theta, and delta – and one more that has been recently discovered now that EEGs are becoming sensitive enough – gamma.
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