Animal models of strabismic amblyopia: physiological studies of visual cortex and the lateral geniculate nucleus

Receptive field properties of visual cortical and lateral geniculate cells were studied in 4 models of amblyopia in the cat: monocular deprivation (MD cats), surgical esotropia (esotropic cats), optically induced concomitant strabismus (stationary prism cats) and optically induced incomitant strabismus (rotating prism cats). Comparison observations were made in normal cats. Recordings in visual cortex indicated a reduction in responsiveness to the treated eye in MD and rotating prism cats. Esotropic and stationary prism cats showed mainly a loss of binocular cells. Recordings in the lateral geniculate nucleus indicated a reduction in the spatial resolving capacity of X-cells driven by the treated eye in MD, esotropic and rotating prism cats. The magnitude of this effect was comparable in all of these preparations. Stationary prism cats showed comparable spatial resolving capacities in X-cells driven by either eye. Y-cells were unaffected in any preparation except MD where there were reduced frequencies of Y-cells driven by the treated eye. These results indicate that: (1) interocular differences in spatial patterns without form deprivation are sufficient to produce a loss of responsiveness to one eye in visual cortex; (2) incomitant disparities are necessary to produce the physiological correlates of amblyopia in cats; and (3) deficits in spatial resolution in geniculate neurons are comparable in magnitude in various amblyopic preparations.