Orientation column

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

Unsupervised learning for the visual cortex (layer IV): model and simulations

Abstract: The authors present a statistical model to study the evolution of orientation columns in layer IV of the visual cortex after birth by simulating, on the retina, the first visual experiences of an animal (darkness, biased, and normal visual environments). The results are consistent with biological experiments. The authors show the necessity of introducing a new nonlinear model in which both vertical and intracortical connections evolve simultaneously as soon as the visual experience begins. The model sets up intracortical connections and achieves the maturation of orientation columns. It takes into account recent neurobiological observations for the development of intracortical connections. Simulations reproduce the results of experiments which observe excitative intracortical connections between cells of similar orientation in different hypercolumns. >

Image processing in the primary visual cortex

Abstract: INTRODUCTION Area 17 or the primary visual area forms the first link in the chain of cerebral analysis of a visual image. The neurones forming the primary visual cortex are characterized by the extreme precision of their connections, functional specialization and hierarchic organization. The spatial precision of the connections within the system for vision permit retinotopic representation in the visual cortex, so that each point of the retina is projected into a specific area of the cortex. The cortical neurones which analyze the characteristics of the image situated in a precise zone of the visual field are themselves organized into a basic functional unit known as a hypercolumn. Within each hypercolumn there are various columnar cell systems with receptive fields having similar characteristics. Thus, each hypercolumn is made up of multiple orientation columns, two ocular dominance columns and 'blob' regions. All these systems permit the analysis of different aspects of the image. The neurones belonging to the orientation columns are sensitive to the orientation, spatial frequency and movement of a visual stimulus; those of the 'blob' regions to colour, and the binocular neurones of the ocular dominance columns to depth. Within each column, the hierarchical pattern of neurone interconnections determines the successive appearance of cells with receptive fields having new properties.