Vestibular contribution to spatial orientation. Evidence of vestibular navigation in an animal model

To determine if animals are capable of utilizing vestibular sensory input for spatial orientation, a six-arm radial maze with a rotating central turntable was constructed. Sprague-Dawley rats were trained on this apparatus by rotating them without visual, auditory, or olfactory cues. Animals were required to locate a reward (located in a constant position relative to the starting position) following random rotations varying from 0 to +/- 360 degrees, growing progressively larger in 60 degrees increments. Normal rats (N = 10) showed a steady improvement in performance over the training and testing period. Bilateral labyrinthectomy (N = 5) produced a profound decrement in that performance (p less than 0.001). When visual cues were added, labyrinthectomized animals improved their performance, but remained significantly below that of normal animals without visual cues (p less than 0.001). Normal animals allowed to use visual cues showed no improvement over their performance without visual cues. The results indicate that rats can utilize vestibular sensory information for navigational purposes. In fact, under these experimental conditions, rats are more successful in utilizing vestibular sensory input for navigation than visual cues.