How the Body Works: REM

Rapid eye movements can be measured by placing an electrode on each side of a sleeping person's eye. Eye movements between the front and the back of the eye cause changes in the electrical potential, which can be recorded on a moving band of paper.

A recording of a person undergoing a dreaming phase of sleep, as illustrated here, shows the only stage at which rapid eye movements occur.

This recording, is of Stage III sleep, which is dreamless.

This recording shows a person whose eyes are closed and who is in a relaxed state.

All readings are measured over a four-second time period