VOR adaptation is essential for ensuring adequate visual acuity during head turns and for restoring proper motor and perceptual orientation in space in response to changes in the organism or its environment, such as occur with growth and development, aging, injury to the peripheral or central nervous system or the donning of a new pair of spectacles.

The proposed experiments examine the neural mechanisms of VOR adaptation through a systematic analysis of the correlation between 1) the patterns of neural activity present in the circuit for the VOR during the induction of learning, 2) the altered activity in the circuit during the expression of learning, and 3) the behavioral changes that are induced.

The VOR is one of many motor systems that are thought to rely on cerebellum-dependent learning to maintain normal sensorimotor function and for recovery of function following injury. The anatomy and physiology of the cerebellum is very regular across the extent of this structure, therefore, the principles uncovered in studies of VOR adaptation may be useful for the development of rational therapeutic approaches for many forms of sensorimotor dysfunction.

Thesaurus Terms:
eye movement, neural information processing, neuroregulation, vestibuloocular reflex biological signal transduction, cerebellar Purkinje cell, cerebellar cortex, cerebellum, head movement, neural plasticity, retina, sensorimotor system, smooth pursuit eye movement, visual stimulus
Macaca mulatta, electrode, single cell analysis, statistics /biometry

Institution: STANFORD UNIVERSITY, STANFORD, CA 94305
Fiscal Year: 2006
Department: NEUROBIOLOGY
Project Start: 30-SEP-1999
Project End: 31-MAY-2008
ICD: NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS
IRG: SMI

LEARNING & MEMORY 11:559-565
©2004 by Cold Spring Harbor Laboratory Press; ISSN 1072-0502/04 $5.00

Reversal of Motor Learning in the Vestibulo-Ocular Reflex in the Absence of Visual Input

Marlene R. Cohen¹, Geoffrey W. Meissner², Robert J. Schafer¹ and Jennifer L. Raymond¹,³

¹ Department of Neurobiology and ² Department of Biological Sciences, Stanford University, Stanford, California 94305, USA

The subjects in this experiment were one female and three male rhesus monkeys (Macaca mulatta; 6-15 kg). Monkey L seemed to have impaired vision in one eye. The eye movements reported for that monkey were recorded in the eye with apparently normal vision.

Using sterile procedures described previously (Lisberger et al. 1994 ; Raymond and Lisberger 1996 ), animals were implanted with an eye coil for measuring vertical and horizontal eye movements and a head holder for restraining the head.

During experiments, animals were seated in a primate chair to which their head holder was secured. Head movement stimuli were delivered using a servo-controlled turntable (Carco) that rotated the animal, the primate chair, and a set of magnetic field coils (CNC Engineering) together about a vertical axis.

All surgical and behavioral procedures conformed to guidelines established by the U.S. Department of Health and Human Services (National Institutes of Health) Guide for the Care and Use of Laboratory Animals (1996) as approved by Stanford University.

VOR Gain Training
Animals were fitted with either 2.2x magnifying or 0.25x miniaturizing goggles, which they wore in their home cages for up to 4 wk. The first experiments were conducted after the monkey had been wearing the goggles for at least 24 h.

Following each day's experiment (which lasted <2 h), animals were returned to the home cage with the goggles on until the next experiment. Experiments were most often separated by 24 h and were never separated by <18 h.

After the animals had worn goggles for a period of several weeks, the goggles were removed and the animals were allowed at least 1 wk to recover in their home cages before more experiments were conducted. After removal of the goggles, the VOR gain returned to normal in 3 d.

Testing Procedures
During an experiment, the animal was seated in a primate chair and its head was restrained using the implanted head holder. The chair was secured to the turntable.

Once the animal's head was fixed, the goggles were removed and the eye coil was calibrated by having the monkey fixate a small visual target at a number of locations. Within 10 min of the goggles being removed, the lights were turned off.

At no time during the setup were the animals allowed to experience combined visual and vestibular stimulation when they were not wearing goggles. All experiments were conducted in a room specially designed to keep all light out, and this was checked periodically by the experimenters by adapting to the darkness in the room for 15 min and searching for stray light.

To further control for possible light leaks into the room, some experiments on Monkey B were conducted while the goggles remained on throughout the hour of head movements in the dark.