Electroencephalogram

Electroencephalography records electrical activity in the brain via electrodes attached to the forehead and scalp. On the right, the electroencephalogram shows normal alpha, beta, theta, and delta waves.

(From KS Saladin, Anatomy and Physiology, 1998, WCB McGraw-Hill, p. 489; with permission.© The McGraw-Hill Companies Inc./Dennis Strete, photographer)