Orientation column

About: Orientation column is a research topic. Over the lifetime, 1142 publications have been published within this topic receiving 130169 citations.

The Design of Striate Cortex

Abstract: Our lack of knowledge about the functions of most regions of the brain makes it difficult to discuss how different parts of it may have evolved, and why particular brain regions are differently organised in different species. It is relatively easy to understand why the shape of a bird’s beak varies from one species to the next, since the function of the beak is understood, but why is the lateral geniculate nucleus of a monkey organised differently from that of a cat or a mouse? A satisfactory explanation of the evolution of the lateral geniculate nucleus (or that of almost any other brain region) is impossible because we have very little idea of what the nucleus is for. Although discussing the evolution of the striate cortex may seem an equally impossible task, we do have some ideas about its possible function, thanks mainly to the work of Hubel and Wiesel, and my purpose in this chapter is to discuss one of their suggestions about what striate cortex does, and to show how this may have influenced some aspects of its design or evolution.

The disinhibitory zone of the striate neuron receptive field and its sensitivity to cross-like figures.

Abstract: Acute experiments on immobilized anesthetized cats were used to confirm the suggestion that the sensitivity of many neurons on the primary visual cortex to cross-shaped, angular, and Y-shaped figures may be determined by the presence within their receptive fields of disinhibitory zones, which block end-stopping inhibition A total of 55 neurons (84 functions, ie, on and off responses) were used for studies of sensitivity to crosses, and responses to single bars of different lengths were compared before and after stimulation of an additional lateral zone of the field (the presumptive disinhibitory zone), which was located in terms of responses to crosses Seventeen of the 55 cells in which increases in the length of a single bar decreased responses, ie, which demonstrated end-stopping inhibition, showed significant increases in responses (by an average factor of 206 ± 016) during simultaneous stimulation of the lateral zone of the receptive field, which we interpreted as a disinhibitory effect on end-stopping inhibition These data provide the first direct evidence for the role of end-stopping inhibition and its blockade by the disinhibitory zone of the receptive field in determining the sensitivity of some neurons in the primary visual cortex of the cat to cross-shaped figures

Models of Simple and Complex Cells

Abstract: The receptive field properties of neurons in the retina and LGN are fairly similar both in their spatial center-surround organization and in their temporal band-pass structure. What happens at the level of primary visual cortex where LGN axons project? The first systematic investigations of cortical visual responses were made by Hubel and Wiesel at the end of the 1950s and early 1960s, taking advantage of newly engineered tungsten electrodes that permitted stable extracellular recordings from nerve cells over long periods of time in awake animals. Similar electrodes have been used over more than sixty years for extracellular recordings in cats and monkeys. Hubel and Wiesel soon discovered that the responses of cortical neurons are much richer than what had been described at earlier stages of visual processing and reported the existence of two major types of cells called simple and complex in the primary visual cortex of the cat. They went on to characterize many other aspects of the representation of visual information by cortical neurons and cell assemblies in primary visual cortex. We will focus here on describing the linear and non-linear properties of simple and complex cell receptive fields as well as some aspects of the transformation of neural signals occurring at the cortical level.