Changes in Human Brain Potentials during the Onset of Sleep.

A-interrupted alpha: the normal waking 10.per-second rhythm dominates the pattern B-Zozu voltage: the alpha rhythm is lost C-spindles: short groups (“spindles”) of 14-per-second waves appear and also random “delta” * waves 0.2 second or more in length D-spindles plus random: both types of wave increase in voltage and the delta waves become longer E-random: the 14.per-second waves become inconspicuous, but delta waves continue to increase in voltage and wavelength