Showing papers on "Orientation column published in 1974"

Sequence regularity and geometry of orientation columns in the monkey striate cortex

Abstract: The striate cortex of the macaque monkey is subdivided into two independent and overlapping systems of columns termed “orientation columns” and “ocular dominance columns.” The present paper is concerned with the orientation columns, particularly their geometry and the relationship between successive columns. The arrangement of the columns is highly ordered; in the great majority of oblique or tangential microelectrode penetrations the preferred orientations of cells changed systematically with electrode position, in a clockwise or counterclockwise direction. Graphs of orientation vs. electrode track distance were virtually straight lines over distances of up to several millimeters; such orderly sequences were often terminated by sudden changes in the direction of orientation shifts, from clockwise to counterclockwise or back. The orientations at which these reversals occurred were quite unpredictable. Total rotations of 180–360° were frequently seen between reversals. In tangential or almost tangential penetrations orientation shifts occurred almost every time the electrode was moved forward, indicating that the columns were either not discrete or had a thickness of less than 25–50 μ, the smallest order of distance that our methods could resolve. In penetrations that were almost perpendicular to the surface, the graphs of orientation vs. track distance were relatively flatter, as expected if the surfaces of constant orientation are perpendicular to the cortical surface. Stepwise changes in orientation of about 10° could sometimes be seen in perpendicular penetrations, each orientation persisting through several clear advances of the electrode, suggesting a set of discrete columnar subdivisions. The possibility of some kind of continuous variation in orientation with horizontal distance along the cortex was not, however, completely ruled out. Occasionally a highly ordered sequence was broken by an abrupt large shift in orientation of up to 90°. Shifts in ocular dominance occurred roughly every 0.25–0.5 mm and were independent of orientation shifts. In multiple parallel penetrations spaced closer than about 250 μ the slopes of the orientation vs. track distance curves were almost the same; reconstruction of these penetrations indicated that the regions of constant orientation are parallel sheets. On crossing perpendicular to these sheets, a total orientation shift of 180° took place over a distance of 0.5–1.0 mm. Column thickness, size of shifts in orientation, and the rate of change of orientation with distance along the cortex seemed to be independent of eccentricity, at least between 2° and 15° from the fovea. A few penetrations made in area 17 of the cat and in area 18 of the monkey showed similar orderly sequences of receptive-field orientation shifts.

Uniformity of monkey striate cortex: a parallel relationship between field size, scatter, and magnification factor.

Abstract: This paper is concerned with the relationship between orientation columns, ocular-dominance columns, the topographic mapping of visual fields onto cortex, and receptive-field size and scatter. Although the orientation columns are an order of magnitude smaller than the ocular-dominance columns, the horizontal distance corresponding to a complete cycle of orientation columns, representing a rotation through 180°, seems to be roughly the same size as a left-plus-right ocular dominance set, with a thickness of about 0.5–1 mm, independent of eccentricity at least out to 15°. We use the term hypercolumn to refer to a complete set of either type (180°, or left-plus-right eyes). In the macaque monkey several penetrations were made at various eccentricities in various parts of the striate cortex subserving the fovea, parafovea and midperiphery. As observed many times previously, in any vertical penetration there was an apparently random scatter in receptive-field positions, which was of the same order of magnitude as the individual receptive fields in that part of the cortex; the field size and the scatter increased in parallel fashion with eccentricity. The movement through the visual field corresponding to a 1 mm horizontal movement along the cortex (the reciprocal of the magnification factor) also increased with eccentricity, in a manner that was strikingly parallel with the increase in receptive field size and scatter. In parts of the cortex representing retina, at least out to about 22° from the fovea, a movement along the cortical surface of about 1 mm was enough to displace the fields so that the new position they collectively occupied half overlapped the old. Such an overlap was thus produced by moving along the cortex a distance about equal to the thickness of a left-plus-right set of ocular-dominance columns, or a complete 180° array of orientation columns. It therefore seems that, independent of eccentricity, a 2 mm × 2 mm block of cortex contains by a comfortable margin the machinery needed to analyze a region of visual field roughly equal to the local field size plus scatter. A movement of 2–3 mm corresponds to a new visual field region and to several new sets of hypercolumns. The cortex thus seems remarkably uniform physiologically, just as it is anatomically.

Neural Basis of Orientation Perception in Primate Vision

Abstract: Orientational differences in human visual acuity can be related parametrically to the distribution of optimal orientations for the receptive fields of neurons in the striate cortex of the rhesus monkey. Both behavioral measures of acuity and the distribution of receptive fields exhibit maximums for stimuli horizontal or vertical relative to the retina; the effect diminishes with distance from the fovea. The anisotropy in the neuronal population and in visual acuity appear to be determined by postnatal visual experience.

An intracellular study of neuronal organization in the visual cortex.

Abstract: Neuronal connections in the visual cortex of cat (areas 17 and 18) were studied with intracellular recording and electrical stimulation techniques under Nembutal anaesthesia. Four types of axonal projection were seen; 1. association efferent cells projecting to adjacent cerebral cortex on the ipsilateral side, 2. commissural efferent cells to visual cortex on the contralateral side, 3. corticofugal efferent cells to the ipsilateral lateral geniculate body and superior colliculus, and 4. non-efferent cells whose projection is confined within the visual cortex. Both association and commissural efferent cells were located in layer III, corticofugal efferent cells in layer V and non-efferent cells in layers II–VI. Upon these cells two types of synaptic actions were exerted by the specific visual afferents that originate from the lateral geniculate body; 1. type I, monosynaptic excitation plus disynaptic inhibition and 2. type II, disynaptic excitation plus trisynaptic inhibition. Type I effects were found in layers III–V, and type II in layers II and VI. In the border region between areas 17 and 18 monosynaptic excitation and disynaptic inhibition were produced also by the commissural efferents originating from the contralateral visual cortex. On the basis of these results, a possible neuronal circuitry in the visual cortex is postulated.

The orientation selectivity of single neurons in cat striate cortex

Abstract: The sensitivity to stimulus orientation — orientation selectivity — of simple and complex neurons in cat striate cortex was studied quantitatively. Orientation selectivity was found to be related to receptive field size — neurons with larger receptive fields being less sensitive to stimulus orientation than those with smaller receptive fields. Simple cells were more orientationally selective than complex cells. The orientation selectivity of simple cells was only weakly related to their receptive field geometry (i.e., receptive field width/length ratio), but simple cells with narrow, elongated excitatory receptive fields are more orientationally selective than those with squarer, excitatory receptive fields. These results indicate that orientation selectivity cannot be accounted for solely by the geometry of the excitatory zones and suggest that inhibitory influences sharpen the tuning of simple striate neurons for stimulus orientation.

Binocular neurons of the rabbit's visual cortex: receptive field characteristics.

Abstract: Using standard electrophysiological techniques, 130 neurons were recorded from the binocular region of the paralysed, unanesthetised rabbit's visual cortex Their receptive fields were categorised into 5 major classes: stationary, motion sensitive, direction selective, double-direction selective and indefinite The majority of the preferred directions of all direction and double direction selective receptive fields were located within±10° of horizontal or vertical Of the 130 neurons studied, 104 (79%) were binocular and 50% of these binocular neurons had non-identical receptive fields on the two retinae The dominance distribution for these binocular neurons revealed a strong tendency toward contralateral dominance, and no ipsilateral monocular neurons were found The retinal locations of the receptive fields of these binocular neurons extended from 51° to 84° posterior to the optic disc The ranges of relative horizontal and vertical “disparity” were calculated for all well-defined binocular receptive fields and found to be 245° and 21°, respectively No evidence of “columnar organisation” was seen for the visual cortex of the rabbit These data are contrasted to similar data on the binocular visual system of the cat, and are also interpreted as evidence of the need for interactions among large populations of neurons within the visual cortex of the rabbit

Ontogenesis of receptive fields in the rabbit striate cortex.

Abstract: The responses of rabbit striate cortex neurons to light or optic nerve shock were tested in 633 units in 54 rabbit pups 3–25 days of age. Units were driven by optic nerve shock at the youngest ages tested, but could not be driven by light until postnatal day eight. It was found that the symmetric receptive field types (concentric, uniform, motion) were present at or near the time of eye opening (10–11 days), while the asymmetric types (directional, simple, complex, oriented-directional) did not appear until several days later. All adult receptive field types were first seen at day 18. Until about day 20, cells with indefinite response properties were much more numerous than in the adult, and it is suggested thab cells with asymmetric receptive fields may differentiate out of the indefinite group. Development of visual response in the striate cortex is markedly retarded when compared to that in the superior colliculus.

Inhibitory zones of receptive fields of the lateral geniculate body and visual cortex of the cat

Abstract: Unit responses to moving strips were investigated. The organization of the inhibitory zones in the receptive fields of the lateral geniculate body and visual cortex of the cat was compared. The response in the receptive field of the lateral geniculate body was inhibited only during simultaneous stimulation of the excitatory and inhibitory zones of the field. Stimulation of the inhibitory zone in the receptive field of the visual cortex was effective for a long time (several hundreds of milliseconds) after stimulation of the excitatory zone. The inhibitory zones of the simple and complex receptive fields of the visual cortex differed significantly. An increase in the width of the strip above the optimal size reduced the inhibitory effect in the complex fields. This was not observed in the simple receptive fields. The functional and structural models of the receptive field of the visual cortex are discussed.