Behavioral Analysis of the Role of Geniculocortical System in Form Vision

Abstract

In looking at the title of this session, I am not certain as to how the work I am going to describe fits in. We have been studying the visual system of cats, and, thus it is not clear whether the experiments I will describe are relevant to higher functions of lower animals, or lower functions of higher animals. Basically, the question that we have been asking is a very simple one, and is derived from the recent advances in the anatomy and physiology of the mammalian visual system: which neural structures are important, or perhaps critical for the seeing of shapes. The first experiment I will describe has been done so many times it is difficult to recount all of the people who have performed it, but perhaps it is best to refer to LASHLEY’s original demonstrations. In a series of studies, LASHLEY (1, 2) studied the role of visual cortex which he believed to be important in vision. The simple paradigm he used was to estimate its role by testing visual behavior before and after removing visual cortex. As you are all no doubt aware, the animals that he tested were marvelously resistant to revealing deficits after rather extensive lesions. These findings forced LASHLEY to put forward a rather weak hypothesis to account for his results: namely, that vision is mediated by structures that are widely scattered through the brain, perhaps through all of it. While there is nothing basically wrong with this idea, it is not a very satisfying conclusion. Somehow, it seems more reasonable to assume that specific functions are mediated by unique brain parts, and recent discoveries in the physiology and anatomy of the brain tend to support such a view.