As an addition to Ian's answer, in The Zombie Survival Guide series which is as close to Romero as you can get (although Brooks goes into a little more detail, if I remember Romero's works correctly), you find the following story:

In order to be promoted, the apprentices in some "ancient zombie fighting order" of samurai had to survive one night in a room filled with live-zombie heads in jars that were kept on shelves on the walls of a room. The proximity (screaming? without vocal chords?) to dozens (hundreds?) of undead would apparently turn most insane in one night.

As an addition to Ian's answer, in The Zombie Survival Guide series which is as close to Romero as you can get (although Brooks goes into a little more detail, if I remember Romero's works correctly), you find the following story:

In order to be promoted, the apprentices in some "ancient zombie fighting order" of samurai had to survive one night in a room filled with live-zombie heads in jars that were kept on shelves on the walls of a room. The proximity (screaming? without vocal chords?) to dozens (hundreds?) of undead would apparently turn most insane in one night.