How patterns of bleached rods and cones become visual perceptual experiences: A proposal

In an attempt to increase information about how mammalian visual systems cr eate a perceptual experience out of a retinal photochemical bleach pattern, this article brings together recent rat physiological data acquired with l arge electrodes, an old cat behavioral experiment, and two complex human be haviors: reading and the reversible blindness people experience when the sc ene being viewed is stabilized on the retinal surface. The outcome suggests this juxtaposition of disparate data sets has been logical, reasonable, an d informative. The link between rats and reading is the fact that both rat and human retinas convert bleach patterns into ganglion cell volleys 3 time s a second. The probable trigger for these episodic retinal volleys is a mo re or less abrupt change in the pattern of bleached rods and cones, and we claim the absence of this trigger when the image is stabilized is responsib le for the blindness. The cat behavioral experiment correlates performance on visual discrimination tasks with the number of nerve fibers remaining af ter lesions of the optic tract. The analysis of the result, which shows tha t as few as 2% of the normal number of nerve fibers supports perfect perfor mance of such tasks, prompts the concept of a second dynamic visual system, operating in parallel with the anatomical nervous system pictured in the t extbooks. The dynamic visual system model, which brings into the foreground important old facts that have been neglected and integrates them with new data, offers a synthesis that may be useful in interpreting classical visua l behavioral phenomena.