The resting EEG is the recording of ongoing spontaneous brain electrical activity while the person being examined is relaxing (the person’s eyes may be open or closed). It is made up of oscillations that are described in terms of frequency, which is the number of times a wave completes its cycle per unit of time. Frequency is measured in Hertz (Hz), which is the number of cycles (i.e., undulations) of the wave per second. EEG oscillations also are described by the magnitude of their voltage (power) measured in microvolts (μV [millionths of a volt]).
