How are brain waves formed?

Neurons in the cerebral cortex have bioelectric activity, often with continuous rhythmic potential changes, which is called spontaneous EEG activity. The cortical EEG recorded by placing the lead electrode on the scalp is called EEG. In animal experiments or surgical patients, the cortical spontaneous EEG recorded by opening the skull and placing the lead electrode directly on the cortical surface is called cortical electrogram. If there are limited potential changes in some areas of the brain under the stimulation of sensory afferent impulses, it is called cortical evoked potential.

According to the speed of frequency, the waveforms of EEG signals can be divided into α wave, β wave, θ wave and δ wave. α wave with faster frequency appears when awake, quiet and eyes closed. There are almost no delta waves with the slowest frequency when adults are awake. Δ wave can also appear in adults with extreme fatigue, sleep and anesthesia. Recording and analyzing brain wave shape is of reference significance for the diagnosis of some brain diseases.

Brain wave is the result of the sum of postsynaptic potentials of a large number of neurons in cerebral cortex, and the formation of synchronous rhythm of brain wave is related to the activity of non-specific projection system in cortical thalamus.