Brainwaves know different frequency ranges. Dynamic synchronic or asynchronic changes measured over a certain number of channels, can refer to certain events such as perception and recognition of images and objects, motoric intention or mental concentration.
The following frequency ranges are typical for EEG reading:
Alpha 7.5-13Hz Alpha waves are associated with relaxation. The amplitude of alpha waves ranges between 10 and 50 mV.
Beta 13-40Hz Beta waves are associated with alertness, arousal, problem solving, and concentration. Beta waves are fast but low amplitude.
Delta 0-4Hz Delta waves are associated with deep sleep. They are a high-amplitude, low-frequency wave, and are generated by the lack of processing by neurons. Delta waves can also be found when examining a comatose patient.
Theta 4-7Hz Theta waves are associated with sleep, but can also be associated with anxiety, epilepsy, and traumatic brain injury.
Mu 7-11Hz Mu rhythms are associated with the motor cortex, and can be used to recognise imaginary motor movement.