Orientation column

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

Visual Processing in the Primate Brain

Abstract: The visual system is the most widely studied and perhaps the best understood mammalian sensory system. Not only have the details of its anatomical features been well described, but the behavior of it neurons have also been characterized at many stages of the neural pathway. This chapter focuses on the visual system of nonhuman primates and deals with the way the primate visual system performs the analysis of various attributes of the visual image and then integrates these attributes into a percept of a visual scene. It shows how such fundamental dimensions of visual stimuli as spatial and temporal variations in luminance and chromaticity are first encoded at the level of the retina, and the manner in which the encoding of other more complex stimulus features, such as motion, complex form and depth, emerge at the level of visual cortex. Finally, modulation of visual cortical activity by such cognitive phenomena as memory and attention are discussed. Keywords: dorsal visual stream; lateral geniculate nucleus; neurophysiology; nonhuman primates; parietal cortex; retina; striate cortex; temporal cortex; ventral visual stream

Developmental Designs and Adult Functions of Cortical Maps in Multiple Modalities: Perception, Attention, Navigation, Numbers, Streaming, Speech, and Cognition.

Abstract: This article unifies neural modeling results that illustrate several basic design principles and mechanisms that are used by advanced brains to develop cortical maps with multiple psychological functions. One principle concerns how brains use a strip map that simultaneously enables one feature to be represented throughout its extent, as well as an ordered array of another feature at different positions of the strip. Strip maps include circuits to represent ocular dominance and orientation columns, place-value numbers, auditory streams, speaker-normalized speech, and cognitive working memories that can code repeated items. A second principle concerns how feature detectors for multiple functions develop in topographic maps, including maps for optic flow navigation, reinforcement learning, motion perception, and category learning at multiple organizational levels. A third principle concerns how brains exploit a spatial gradient of cells that respond at an ordered sequence of different rates. Such a rate gradient is found along the dorsoventral axis of the entorhinal cortex, whose lateral branch controls the development of time cells, and whose medial branch controls the development of grid cells. Populations of time cells can be used to learn how to adaptively time behaviors for which a time interval of hundreds of milliseconds, or several seconds, must be bridged, as occurs during trace conditioning. Populations of grid cells can be used to learn hippocampal place cells that represent the large spaces in which animals navigate. A fourth principle concerns how and why all neocortical circuits are organized into layers, and how functionally distinct columns develop in these circuits to enable map development. A final principle concerns the role of Adaptive Resonance Theory top-down matching and attentional circuits in the dynamic stabilization of early development and adult learning. Cortical maps are modeled in visual, auditory, temporal, parietal, prefrontal, entorhinal, and hippocampal cortices.

Double orientation tuning of visual cortex neurons in the cat

Abstract: Orientation tuning of 148 visual cortex neurons was investigated in immobilized unanaesthetized cats. The light slit of the optimal size flashing in the receptive field was used as a stimulus. It was found that 88 neurons (59%) had double orientation tuning: preferred and additional. Additional orientation was either orthogonal or at a sharp angle to the preferred orientation. In 64% neurons double orientation was found only after a change of the contrast between stimulus and background. This kind of tuning in many neurons appeared only at definite moments after the beginning of the stimulus. Model analysis showed that double orientation tuning might be a consequence of the specific structure of neuronal receptive fields. The functional meaning of double orientation tuning and its role in the detection of visual images signs are discussed.