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
The Stealers of Dreams typical. Then the Doctor is there, and asks to talk to him, go into the building and try to help. Once the Doctor gets inside, Jack fills him in on what's happening. Rose is in a room, still unsure of herself. The Doctor tells her about the microorganisms, how they feed off electrical activity, and seem to just love the neuroelectro-chemical signals put out by the right side of adult human brains. They create a feedback loop, which passes to the left side and causes a person to become 'fantasy-crazy.' He tells her that now that she understands what is