Abstract: DESCRIPTION (provided by applicant):
The vestibulo-ocular reflex (VOR) stabilizes gaze and hence foveal images during head movements. Deficits in the VOR resulting from disease or changes in development can severely impair vision. Neural adaptation in the VOR is essential to overcome these deficits. Over the past several decades, the investigation of the VOR and its adaptation has been focused on the contributions of brainstem and cerebellar pathways. The contributions of cerebral cortex in the VOR, however, remain largely unexplored. Recent studies have demonstrated that the frontal eye field (FEF) has direct projections to brainstem VOR pathways and neurons in the subregion of the FEF linked to smooth eye movements (FEFsem) exhibit activity related to both eye movements and head movements, suggesting an important role for the FEFsem in the VOR. The objective of the proposed research is to employ single unit recording and chemical lesion approaches to study the contributions of the FEFsem in the generation and adaptation of the VOR. The first aim is to use single unit recording techniques to quantitatively analyze how the FEFsem neurons encode head motion in monkeys. Recently, we have developed a paradigm that induces robust short-term and long-term plasticity in the VOR that compensates for translational head movements (TVOR). A novel feature of the paradigm is that these behavioral changes are not guided by visual information but by the spatial context of the task, i.e. whether the target is stationary in space or fixed relative to the head. The second aim is to take advantage of this paradigm to study the role of the FEFsem neurons in the generation of the TVOR. This experiment will provide greater understanding of the FEFsem in the information processing related to the task context and in the voluntary control and adaptation of the TVOR. The third aim is to assess the functional significance of the FEFsem by reversibly inactivating the FEFsem and studying its effect on the generation and adaptation of the TVOR. This research will provide important knowledge for understanding the fundamental vestibular and oculomotor neurophysiology and improving the diagnosis and treatment of vestibular disorders in humans.

Thesaurus Terms:
eye movement, head movement, neural information processing, neural plasticity, vestibuloocular reflex, visual field auditory stimulus, biological signal transduction, cerebral cortex, muscimol, neurophysiology, neuropsychology, smooth pursuit eye movement, space perception Macaca mulatta, electrode

Institution: UNIVERSITY OF MISSISSIPPI MEDICAL CENTER, 2500 N STATE ST, JACKSON, MS 39216
Fiscal Year: 2006
Department: OTOLARYNGOLOGY AND COMMUNICATIVE SCIENCES
Project Start: 20-SEP-2002
Project End: 31-AUG-2008
ICD: NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS
IRG: IFCN

The Journal of Neuroscience, May 15, 2003, 23(10):4288-4298

Rapid Motor Learning in the Translational Vestibulo-Ocular Reflex

Wu Zhou,^1,2,3 Patrick Weldon,² Bingfeng Tang,² and W. M. King<sup>2,3,4

1</sup>Department of Otolaryngology and Communicative Sciences, University of Mississippi Medical Center, Jackson, Mississippi 39216, ²Department of Neurology, University of Mississippi Medical Center, Jackson, Mississippi 39216, ³Department of Anatomy, University of Mississippi Medical Center, Jackson, Mississippi 39216, and ⁴Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan 48109

Animal preparation for eye movement recordings. Data reported here were collected from six monkeys (Macaca mulatta) that were prepared for chronic recording of binocular eye movements in multiple staged surgical procedures. First, a stainless steel receptacle was implanted on the animal's skull so that the animal's head could be stabilized with respect to the vestibular stimulator and the electromagnetic field of the eye coil system. An eye coil was implanted on one eye during the surgery (Robinson, 1963 ; Judge et al., 1980 ). During a second surgery, performed after the animal was trained to fixate visual targets, a second coil was implanted on the other eye for binocular recording of eye movements and to control vergence eye position. After recovery from surgery, the monkeys were brought to the laboratory for training or experiments. In the laboratory, the monkey was comfortably seated in a custom-fabricated monkey box mounted on the vestibular stimulator. The field coils and the monkey's head were stabilized relative to the main axis of the vestibular stimulator. The head was stabilized by attaching a stainless steel rod to the post implanted on the monkey's head. The stainless steel rod did not introduce any appreciable distortion of the magnetic field used by the search coil system. The eye coil was calibrated by placing targets at known positions (±20°, every 5°) and requiring the monkey to fixate these positions with its head fixed. An eye coil calibration was performed at the start of each experimental day.

Monkeys were trained to fixate and track visual targets in exchange for fruit juice rewards.