Control of eye movements while recording from single units in the pigmented rat

Abstract

RESEARCH NOTE CONTROL OF EYE MOVEMENTS WHILE RECORDING FROM SINGLE UNITS IN THE PIGMENTED RAT CAROL M. CICERONE and DA~VIEL G. GREEX Vision Research Laboratory, University of Michigan. Ann Arbor. MI 43103, U.S.A. (Receiced 29 November We report here that in the rat, even under deep Many investigators report recording from single units urethane anesthesia. there are large eye movements in the rodent visual pathway without neuromu~uIar which are not eliminated by the mechanical means relaxants to immobilize the eye. This is in contrast to the situation in the cat where it has been shown of cutting the conjunctiva and sewing on an anchored that neuromuscular blocking agents are required to full eye ring. Neuromuscular blocking agents are required to reduce the movements to a tolerable level. reduce eye movements to a tolerable level (Cleland In addition, we show that with well-regulated and Enroth-CugelI, 1966; Rodk but by locating ing agents were used. A typical result is shown at the projection of the optic disc, she finds slow drifts the top of Fig 1. The elapsed time between each con- of no more than 2 to 3 degihr which were within secutive pair of labeled points is 30min. In the first the tolerance necessary for her experiments. Driiger half hour, eye movements were recorded every j min; thus speculates that large slow drifts may be an arti- in the second half hour, every 15 min. Close monitor- fact caused by glue irritation or the weight of the ing of eye movements is important. If movements had mirror. However, Drfiger and Hubel (1976) report been tracked less closely, say once every hour, then that if tectal coordinates were remapped 3-5 hr after in this example only points a and c would have been the original mapping, a general shift of the projection recorded. An underestimate of eye movements would of up to 15’ in one direction was found. Atthough have been made. Large, slow drifts in one direction Drager and Hubel believe swelling of tissue is the as shown in this record were typical. Also typical were most likely cause for the shift, as they also point out, patterns of movement which included large drifts and eye movements can well account for the observation. intervening periods of up to an hour with very little DrPger also attempted the use of Flaxedil, a neuro- motion. Under this condition, we have recorded slow muscular blocking agent. Without careful regulation drifts of up to 4.5 deg/hr. of the respiration volume, she found unresponsive or With the same preparation we now infused a solu- epileptiform discharges from the cortex, and thus she tion similar to that used in cat (e.g. Rodieck, Pet- abandoned the use of Flaxedil. tigrew. Bishop and Nikara. 1967; Enroth-Cugell and 9a>