Head direction cells form the brain's internal compass

Correct: B — It fires only when the animal's head points in a specific compass direction, regardless of location

Taube, Muller, and Ranck (1990) reported neurons in the rat postsubiculum that fired vigorously when the animal's head pointed in a particular allocentric direction — north, say — regardless of where the animal was in the environment or what it was doing. Each cell had its own preferred direction, and together they form an internal compass. Subsequent work has identified head direction cells throughout the limbic system (anterior thalamus, retrosplenial cortex, entorhinal cortex), and they remain stable across visits to the same environment but rotate in concert when prominent landmarks are moved — anchoring the internal compass to external cues.