Hersengolven

Brain waves are the patterns of electrical activity resulting from the action of millions of neurons.

An electroencephalogram, or EEG, is a visual representation of brain waves measured by placing electrodes on the head. It is used to study brain function and disorders; the absence of brain waves on an EEG indicates brain death.

An EEG can show four types of brain waves: alpha, beta, theta, and delta waves.

Alpha waves are low-amplitude rhythmic waves with an 8-13 Hz frequency. They appear in healthy adults' EEGs during wakeful rest but diminish during sleep or concentration.

Beta waves have a frequency of 14-30 hertz. They are observed when a person is mentally alert and focuses on specific tasks.

Theta waves have a frequency of 4-7 hertz. They are typically present in children. In adults, they can show up during emotional stress and transiently during sleep.

Delta waves are high-amplitude and low-frequency waves present in sleeping adults and awake infants. In wakeful adults, delta waves may also signal brain damage.