Integration in the head-direction system is a computation by which horizontal  angular head velocity signals from the vestibular nuclei are integrated  to yield a neural representation of head direction. In the thalamus,  the postsubiculum and the mammillary nuclei, the head-direction  representation has the form of a place code: neurons have a preferred  head direction in which their firing is maximal [Blair and Sharp, 1995,  Blair et al., 1998, ?]