Electrical Microstimulation of the Superior Colliculus in Strabismic Monkeys.
Visually guided saccades are disconjugate in human and nonhuman strabismic primates. The superior colliculus (SC) is a region of the brain topographically organized in visual and motor maps where the saccade goal is spatially coded. The present study was designed to investigate if a site of stimulation on the topographic motor map was evoking similar or different saccade vectors for each eye.



We used microelectrical stimulation (MS) of the SC in two strabismic (one esotrope and one exotrope) and two control macaques under binocular and monocular viewing conditions. We compared the saccade amplitudes and directions for each SC site and each condition independently of the fixating eye and then between each fixating eye. A comparison with disconjugacies of visually guided saccades was also performed.



We observed different saccade vectors for the two eyes in strabismic monkeys, but conjugate saccades in normal monkeys. Evoked saccade vectors for the left eye when that eye was fixating the target were different from those of the right eye when it was fixating. The disconjugacies evoked by the MS were not identical but similar to those observed for visually guided saccades especially for the dominant eye.



Our results suggest that, in strabismus, the saccade generator does not interpret activation of a single location of the SC as the same desired displacement for each eye. This finding is important for advancing understanding of the development of neural circuits in strabismus. French Abstract.
Washington National Primate Research Center, University of Washington, Seattle, Washington, United States 2Department of Ophthalmology, University of Washington, Seattle, Washington, United States.
Jérome
J
Fleuriet
Washington National Primate Research Center, University of Washington, Seattle, Washington, United States.
Mark M G
MM
Walton
Faculty of Health and Sport Science, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Seiji
S
Ono
Washington National Primate Research Center, University of Washington, Seattle, Washington, United States 2Department of Ophthalmology, University of Washington, Seattle, Washington, United States 4Department of Biological Structure, University of Washing.
Michael J
MJ
Mustari
D000818:Animals; D004195:Disease Models, Animal; D004599:Electric Stimulation Therapy / Q000379:methods*; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D008839:Microelectrodes; D013285:Strabismus / Q000503:physiopathology / Q000628:therapy*; D013477:Superior Colliculi / Q000503:physiopathology*; D016896:Treatment Outcome; D015348:Vision, Binocular / Q000502:physiology*