Central organization of the efferent supply to the labyrinthine and lateral line receptors of the dogfish.

Neurons that provide the efferent innervation of the inner ear and lateral line were located in the brain by applying horseradish peroxidase to appropriate cranial nerves. The efferent neurons are found in a rhombencephalic nucleus, called here the octavolateralis efferent nucleus, which lies at the rostral pole of the visceromotor column. Up to 40% of these neurons are contralateral. The location of efferent cells is not topographically related to the sense organs they innervate. Their axons leave the brain together with other motor axons in the facial and glossopharyngeal nerves and there is evidence that some neurons innervate both the ear and the lateral line. The efferent nucleus receives direct sensory input from the labyrinth, but not from the lateral line. The organization of the efferent neurons and the distribution of their axons indicates that their effect on the sense organs is probably widespread and nonspecific.