Eye movements evoked by electrical stimulation in the superior colliculus of rats and hamsters

Although the organization of the sensory representations in the rodent superior colliculus is known to be similar to that of more advanced mammals, little is known about collicular motor organization in these animals. Since it has been suggested that rodents make head, rather than eye, movements to facilitate visual orientation, fundamental organizational dissimilarities could exist in the superior colliculi of different species to underlie these different orientation preferences. However, we observed that electrical stimulation of the rodent colliculus evoked the same pattern of movements observed in other mammals. Conjugates, contraversive saccadic eye movements were evoked and were found to be topographically organized. In addition vibrissa and pinna movements could also be evoked. Although some species difference in evoked movements were evident, the same pattern of motor representations appears to exist in widely disparate mammalian species.