My 50 Year Odyssey to Develop Behavioral Methods to Let Me See Quickly How Well Kittens See

Abstract

The importance of animal models to an understanding of the development and plasticity of visual functions was evident from the outset of the long experimental collaboration of David Hubel and Torsten Wiesel in the early 1960s. Their initial work on kittens had massive impact in part because of the recognition that kittens share with primates substantial similarities of visual system organization and plasticity (e.g., eye-specific lamination of the thalamus and columnar organization of the visual cortex), as well as comparable visual abilities (including stereoscopic vision). In addition the plasticity demonstrated in response to early periods of selected visual exposure provided a glimpse into the origins of amblyopia. Five decades ago my laboratory developed a method for the fast measurement of visual thresholds in kittens in order to capture the consequences for spatial vision of the rapid physiological changes that occurred in the visual cortex during both typical development and those that follow various forms of early selected visual exposure. This paper describes the further evolution of the method with an emphasis on the testing procedures that enable fast capture of spatial visual thresholds such as visual acuity on every animal and occasion. In these respects, the method emulated features of basic tests of human spatial vision as applied in clinical settings. As with clinical tests for humans, the method includes benchmarks of low vision necessary to document the profound immediate consequences of early selected visual deprivation and the speed and extent of the subsequent recovery.

Keywords: critical period; darkness; vision; visual acuity; visual deprivation.

Figure 1.

Photograph of a 4-week-old young kitten scrambling to the floor from a box only 2.9 cm high. The same kitten was unable to descend to the floor from the next highest box (5 cm high). This kitten was deemed too young to initiate training on the jumping stand on that day.

Figure 2.

A photograph of an updated early model of the jumping stand where letters are used to designate key features. The scale bar is 20 cm long. A kitten is placed on the platform (B) and guided gently into the open-ended box (A) to jump toward the vertical grating below for a food reward accompanied by verbal praise and petting. The distance of the jumping platform to the stimuli can be adjusted in large steps by use of boxes of various sizes (G1 and G2) and in smaller continuous amounts by adjustment of the extension of two yoked laboratory jacks (C). If the kitten jumps instead to the adjacent horizontal grating (an error), it is placed immediately on the platform to repeat the trial without any reward. The gratings, illuminated by the lamp (L), are placed on two adjacent closed trapdoors (D) separated by a divider (F) that is 1 cm wide.