Emory University, Atlanta, GA

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Stop Animal Exploitation NOW!
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"Exposing the truth to wipe out animal experimentation"

Government Grants Promoting Cruelty to Animals

Emory University, Atlanta, GA

VALLABH E. DAS - Primate Testing - 2006

Grant Number: 5R01EY015312-03
PI Information: ASSISTANT PROFESSOR VALLABH E. DAS, vdas@rmy.emory.edu 

Abstract: DESCRIPTION (provided by applicant):
Binocular alignment must be maintained in the horizontal, vertical and torsional planes to ensure binocular sensory fusion. Normal development ensures binocular alignment during fixation and binocular coordination during eye movements. Unfortunately, abnormal visual experience during development usually leads to ocular misalignment (strabismus). In fact, various studies have reported the incidence of strabismus to be about 2-5% of the infant population. Data from strabismic humans and from strabismic monkeys in our laboratory have shown that ocular misalignment is accompanied by a lack of conjugate eye movements. Though strabismus is most often associated with a horizontal misalignment, often a combined horizontal, vertical and torsional misalignment is observed. Along with the static horizontal, vertical and torsional misalignment, there appears to be substantial dynamic cross-talk between the principal eye movement planes. In the clinical literature these apparent cross-axis interactions are usually described as 'A' and 'V' patterns of strabismus. Unfortunately, there is a lack of understanding of the neural or mechanical bases for these cross-axis movements, the putative relationship or lack thereof to the neural control of horizontal, vertical or torsional eye movements and the relationship to the etiology of the strabismus. Competing hypotheses include static malpositioning of extraocular muscle pulleys, sideslip of extraocular muscles and muscle pulleys, torsional control of eye movements gone awry leading to apparent muscle dysfunction and finally simply unexplained overaction/underaction of individual extraocular muscles. The goal of our studies is to clarify static and dynamic properties of cross-axis movements and examine its source in animals with a sensory induced strabismus. Our approach will include structural imaging of extraocular muscle to determine role of muscle pulleys; behavioral experiments to examine control of torsion and Listing's laws; neurophysiological experiments to examine the role of motor and pre-motor structures in the brain and biomechanical modeling of extraocular musculature to simulate experimental data. Completion of our studies will be of benefit to the understanding and treatment of certain types of strabismus.

Thesaurus Terms:

binocular vision, eye coordination disorder, eye movement biomechanics, disease /disorder model, extraocular muscle, oculomotor nuclei Macaca mulatta, magnetic resonance imaging

Fiscal Year: 2006
Department: NEUROLOGY
Project Start: 01-FEB-2004
Project End: 31-JAN-2008

J Neurophysiol 93: 108-116, 2005. First published August 18, 2004

Modeling of Smooth Pursuit-Related Neuronal Responses in the DLPN and NRTP of the Rhesus Macaque
Seiji Ono1, Vallabh E. Das1,2, John R. Economides3 and Michael J. Mustari1,2
1Division of Visual Science, Yerkes National Primate Research Center and 2Department of Neurology, Emory University, Atlanta, Georgia; and 3Beckman Vision Center, University of California, San Francisco, California

Submitted 8 June 2004; accepted in final form 13 August 2004

Surgical procedures
A detailed description of our surgical procedures can be found in earlier publications (Mustari et al. 1988 , 1997 , 2001 ). Behavioral and single-unit data were collected from two normal juvenile rhesus monkeys (Macaca mulatta) weighing 45 kg. Surgical procedures, carried out under aseptic conditions using isoflurane anesthesia (1.252.5%), were used to stereotaxically implant a stainless steel head-stabilization post (Crist Instruments) and stainless steel recording chambers. In the same surgery, a scleral search coil for measuring eye movements (Fuchs and Robinson 1966 ) was implanted underneath the conjunctiva of one eye using the technique of Judge et al. (1980) . All surgical procedures were performed in strict compliance with National Institutes of Health guidelines and the protocols were reviewed and approved by the Institutional Animal Care and Use Committee at Emory University.

Behavioral paradigms
During all experiments, monkeys were seated in a chair with the head stabilized in the horizontal stereotaxic plane. Neurons in the DLPN and rNRTP were first classified as visual or smooth-pursuit related. We tested neurons for visual sensitivity by requiring the monkey to fixate a stationary target while a large-field visual stimulus was moved in eight cardinal directions separated by 45. Only neurons that responded during horizontal or vertical smooth pursuit of a small-diameter (0.2) target spot moving at low frequency (0.10.75 Hz; 10) were included in this study. All neurons were tested as monkeys tracked a target that moved with a step-ramp trajectory with a constant velocity ramp (1030/s) over a dark background. The size of the step was adjusted so that smooth pursuit was initiated without initial saccades (Rashbass 1961 ). Usually the size of the step was between 2 and 4. Data collected during step-ramp testing were used for the model fitting procedure described in the following text.

* Fuchs and Robinson 1966

Please email:  VALLABH E. DAS, vdas@rmy.emory.edu to protest the inhumane use of animals in this experiment. We would also love to know about your efforts with this cause: saen@saenonline.org

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Rats, mice, birds, amphibians and other animals have been excluded from coverage by the Animal Welfare Act. Therefore research facility reports do not include these animals. As a result of this situation, a blank report, or one with few animals listed, does not mean that a facility has not performed experiments on non-reportable animals. A blank form does mean that the facility in question has not used covered animals (primates, dogs, cats, rabbits, guinea pigs, hamsters, pigs, sheep, goats, etc.). Rats and mice alone are believed to comprise over 90% of the animals used in experimentation. Therefore the majority of animals used at research facilities are not even counted.

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