Any of the electrical waves from the parietal and occipital regions of the brain, having frequencies from 8 to 13 hertz. It is a sign of relaxation, since they indicate a lack of sensory stimulation in a conscious person.

Alpha waves are higly regular waves found in an EEG or ERP record of a drowsy individual. While present, interpretation of EEGs and ERPs almost impossible, as the drown out most waveforms due to their high amplitude. They are not easily filtered from a record.