Neural and behavioral effects of early eye rotation on the optokinetic system in the wallaby, Macropus eugenii

1. Total optokinetic responses measured by electro-oculography and single unit recordings from the nucleus of the optic tract and dorsal terminal nucleus (NOT-DTN) of the accessory optic system were taken from young adult wallabies, whose one eye had been rotated about the optic axis at birth, and were compared with those from normal controls. 2. The velocities of the horizontal component of the slow phases of optokinetic nystagmus were measured in the horizontal plane as a function of the direction of stimulus motion. In normal animals the overall gain during monocular stimulation was greatest for horizontal temporonasal movement, with a lesser response to movement in the opposite, nasotemporal, direction. Upward or downward vertical stimulus motion did not elicit horizontal responses. In animals where one eye was removed at birth and the other eye was normal, the characteristic bidirectional response was retained; the response was identical with that elicited from one eye of a normal animal. 3. After surgical rotation (extorsion) of the left eye by approximately 90 degrees on or within a few days of birth, the animals were grown to adulthood. The visual streak of the retina of the operated eye was then found, in individual cases, to be between 30-100 degrees from horizontal with the head held in the standard resting position. This angle was taken as the definitive degree of cyclotorsion resulting from the operation in each animal. The extraocular muscles connected with regions of the eye adjacent to the location of their outgrowth in the orbit and not with the normal point of attachment on the globe.(ABSTRACT TRUNCATED AT 250 WORDS)