Orientation column

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

The representation of three‐dimensional visual space in the cat's striate cortex

Abstract: 1. Binocularly driven single units were recorded in the cat's striate cortex. For each neurone the two monocular receptive fields were stimulated simultaneously in order to assess the optimal positioning of the image in both eyes to give the best binocular response. 2. The electrode was driven perpendicular to the surface of the brain to explore cortical columns, all the cells of which are known to have the same preferred target orientation. 3. All orientation columns were found to fit into one of two classes according to their binocular organization. 4. In a constant depth column the receptive fields of binocular neurones cover a small retinal area and they are laid out in almost identical arrays in the two eyes. Consequently, the horizontal disparity is practically the same for all the units. The depth column as a whole is viewing a thin sheet of visual space, a few degrees wide, floating at some distance from the cat. There may be about 0·6° disparity difference between neighbouring depth columns. 5. In a constant direction column the binocular units' fields are all super-imposed on the retina contralateral to the hemisphere containing the column. In the ipsilateral eye they are more scattered horizontally. Therefore the horizontal disparity varies enormously from cell to cell and the column as a whole is viewing a cylinder of visual space directed towards the contralateral eye. Neighbouring direction columns may vary by about 4° in their oculocentric visual direction. 6. This columnar arrangement is probably important for space perception in the cat. Activity in only one depth and one direction column would specify the orientation and the three-dimensional locus of an object in space. 7. The two types of column may be involved in the control of disjunctive and conjugate eye movements.

Laminar differences in the orientation selectivity of geniculate afferents in mouse primary visual cortex

Abstract: It has been debated whether orientation selectivity in mouse primary visual cortex (V1) is derived from tuned lateral geniculate nucleus (LGN) inputs or computed from untuned LGN inputs. However, few studies have measured orientation tuning of LGN axons projecting to V1. We measured the response properties of mouse LGN axons terminating in V1 and found that LGN axons projecting to layer 4 were generally less tuned for orientation than axons projecting to more superficial layers of V1. We also found several differences in response properties between LGN axons and V1 neurons in layer 4. These results suggest that orientation selectivity of mouse V1 may not simply be inherited from LGN inputs, but could also depend on thalamocortical or V1 circuits.

Topographic organization of the orientation column system in the striate cortex of the tree shrew (Tupaia glis). II. Deoxyglucose mapping.

Abstract: The topographic organization of the orientation column system in the tree shrew striate cortex was examined by using 2-deoxyglucose autoradiography to map the cortical sites of increased metabolic activity produced by visual stimulation with stripes of a single orientation. Awake experimental tree shrews (freely moving, restrained, or paralyzed) were given injections of deoxyglucose label and then stimulated with vertical, horizontal, or oblique stripes for 45--75 min. Autoradiographs of coronal sections through the striate cortex revealed regularly spaced radial zones of increased deoxyglucose uptake 150--350 micrometers wide, extending from the cortical surface to the white matter, separated by interzone regions of lower uptake. The radial zones were most densely labeled and distinct in layers I--IIIb and least distinct in layer IV, which was continuously and densely labeled throughout both the radial zone and interzone regions. These radial zones, which were not present in control animals that viewed many orientations, reflect the locations of cortical cells activated by a single stimulus orientation. Reconstructions of the radial zones from serial sections produced maps of the distribution of increased deoxyglucose uptake across striate cortex. The maps reveal a highly organized system of narrow, parallel bands that are slightly wavy and have a mean spacing of 530 micrometers. The band pattern was confirmed in sections cut tangential to the cortical surface and was similar in animals stimulated with either vertical or horizontal stripes; the bands consistently abut the 17--18 border at nearly right angles and extend across the striate cortex in a generally posteromedial direction. These patterns of increased deoxyglucose consumption confirm the anisotropic distribution of orientation-selective cells across the tree shrew striate cortex, suggested in the preceding microelectrode study (Humphrey and Norton, '80). The density distribution of label within the bands further suggests that the anisotropy is due to a system of parallel, somewhat wavy iso-orientation lines arranged roughly perpendicular to the 17--18 border.

Anatomy and physiology of the afferent visual system.

Abstract: The efficient organization of the human afferent visual system meets enormous computational challenges. Once visual information is received by the eye, the signal is relayed by the retina, optic nerve, chiasm, tracts, lateral geniculate nucleus, and optic radiations to the striate cortex and extrastriate association cortices for final visual processing. At each stage, the functional organization of these circuits is derived from their anatomical and structural relationships. In the retina, photoreceptors convert photons of light to an electrochemical signal that is relayed to retinal ganglion cells. Ganglion cell axons course through the optic nerve, and their partial decussation in the chiasm brings together corresponding inputs from each eye. Some inputs follow pathways to mediate pupil light reflexes and circadian rhythms. However, the majority of inputs arrive at the lateral geniculate nucleus, which relays visual information via second-order neurons that course through the optic radiations to arrive in striate cortex. Feedback mechanisms from higher cortical areas shape the neuronal responses in early visual areas, supporting coherent visual perception. Detailed knowledge of the anatomy of the afferent visual system, in combination with skilled examination, allows precise localization of neuropathological processes and guides effective diagnosis and management of neuro-ophthalmic disorders.