Head direction cells efference copy") preparing the network for an impending head turn. HD cells continue to fire in an organized manner during sleep, as if animals were awake. However, instead of always pointing toward the same direction—the animals are asleep and thus immobile—the neuronal "compass needle" moves constantly. In particular, during rapid eye movement sleep, a brain state rich in dreaming activity in humans and whose electrical activity is virtually indistinguishable from the waking brain, this directional signal moves as if the animal is awake: that is, HD neurons are sequentially activated, and the individual neurons representing a common direction during wake
Pinky and the Brain Labs research facility. Brain is self-centered and scheming, Pinky is good-natured but feebleminded. In each episode, Brain devises a new plan to take over the world which ultimately ends in failure: usually due to Pinky's idiocy, the impossibility of Brain's plan, Brain's own arrogance, or just circumstances beyond their control. In common with many other "Animaniacs" shorts, many episodes are in some way a parody of something else, usually a film or novel. Many of the "Pinky and the Brain" episodes occur in the 1990s at Acme Labs, located in some large American city underneath a suspension bridge. Several episodes