Neuronal pathways involved in the optokinetic head nystagmus of the frog

The morphology of projection neurons in the basal optic nucleus and the pretectal area and the interconnections of these brain regions were studied with the aid of the cobalt-filling technique. It was found that the nucleus-sends long descending axons to the medullary reticular formation. The two basal optic nuclei are reciprocally interconnected and do not give a direct descending pathway. The pretectal nuclei and the basal optic nucleus are also reciprocally coupled. It is supposed that the described pathways mediate commands for horizontal and vertical nystagmic head movements.