Orientation column

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

Sequential change in receptive fields of striate neurons in dark adapted cats

Abstract: 1. A general purpose, digital computer was employed to map quantitatively the receptive fields of units in cat's striate cortex. 2. Receptive fields were studied as a function of barbiturate anesthetic level under dark adapted conditions. 3. Receptive fields obtained from lateral geniculate axons were topographically simple and usually represented a single peak with concentric zones of decreasing excitability. Such fields were stable under all anesthetic and electroencephalographic conditions. 4. Responses were recorded from striate cells, both simple and complex in the sense of Hubel and Wiesel. These demonstrated varied field configurations such as an excitatory cylinder in an inhibitory field, excitatory vertical axis flanked by asymmetric inhibitory areas, and more complex patterns including potentially direction and velocity sensitive ones. 5. Many cortical maps were unstable over time, especially in the presence of low voltage, fast electroencephalographic activity. Changes were not random nor did they represent simple linear displacements of peaks, but included axis shifts, gradient change, and expansion or contraction of excitatory and inhibitory zones with centers at fixed relative positions. 6. Heavy barbiturate anesthesia and spontaneous spindling in the EEG markedly reduced the variability in these maps; the encephale isole preparation was more stable than spinally intact animals. This association suggests a role of the midbrain reticular formation in cortical variability. 7. Random rather than iterative presentation of matrix points resulted in higher mean firing rates and more stable receptive fields, probably the result of photochemical recovery in dispersed receptors and time averaging of cellular excitability. 8. When stability was analyzed as a function of time interval of response (early on, late on, early off, late off), initial on responses were often more stable than longer latency late on- or off-responses. This factor, among others discussed, makes eye movement an unlikely explanation for map variability. It suggests additionally that late on- and off- responses represent input to the cortical cell from units other than those producing the early on-response. 9. The effects of pentobarbital, in addition to stabilization of the receptive field, included striking phase reversals in which inhibitory regions became excitatory and visa versa. Firing rate often changed substantially, but both increases and decreases were observed. 10. It is argued that visual response under pentobarbital is a special and not the general case of visual perception and that sequential receptive field changes during aroused brain states reflect integrative, purposive processes at the cortical level.

Spontaneous symmetry breaking in self–organizing neural fields

Abstract: We extend the theory of self-organizing neural fields in order to analyze the joint emergence of topography and feature selectivity in primary visual cortex through spontaneous symmetry breaking. We first show how a binocular one-dimensional topographic map can undergo a pattern forming instability that breaks the underlying symmetry between left and right eyes. This leads to the spatial segregation of eye specific activity bumps consistent with the emergence of ocular dominance columns. We then show how a 2-dimensional isotropic topographic map can undergo a pattern forming instability that breaks the underlying rotation symmetry. This leads to the formation of elongated activity bumps consistent with the emergence of orientation preference columns. A particularly interesting property of the latter symmetry breaking mechanism is that the linear equations describing the growth of the orientation columns exhibits a rotational shift-twist symmetry, in which there is a coupling between orientation and topography. Such coupling has been found in experimentally generated orientation preference maps

Perceptual capacity of the isolated visual cortex in the cat

Abstract: The split-brain approach was utilized in 6 cats to test the degree of functional autonomy in the visual system. The central visual cortex of one hemisphere was isolated by the removal of most of the extravisual neocortex of the same hemisphere. Visual inflow was restricted to the isolated side in four cases by sectioning the crossed optic fibres at the chiasma and masking one eye and in two cases by section of the contralateral optic tract. The isolation produced severe deficits in visual performance, although all cases retained some ability to learn and to recall simple pattern discriminations. The results of two- and three-stage removals of the non-visual cortex, and of terminal section of the callosum, as well as histology of the lateral geniculate nucleus indicated that geniculo-striate damage was not the limiting factor. Removal of fronto-parietal cortex produced as much or more decrement in visual discrimination than did removal of temporal cortex.

Genetic instructions and developmental plasticity in the kitten's visual cortex.

Abstract: Two major properties of neurons in the kitten's visual cortex, binocularity and orientation selectivity, are present when the eyes first open, and therefore can be established by genetic instructions alone. However, both of these attributes require visual experience for their maintenance or strengthening; and both can be rapidly modified by unusual kinds of experience. Alternating sequences of cells dominated by one eye, then the other, can be recorded during penetrations through the cortex in binocularly deprived kittens, typical of the 'ocular dominance columns' of the normal adult cat. However, if one eye is deprived by lid-suture, the entire visual cortex becomes strongly dominated by the open eye. Experiments in which each eye saw separately through a transparent neutral density filter or a translucent diffuser showed that this phenomenon is caused not by the reduction in retinal illumination, but by the abolition of contrast in the deprived eye. A study of the retrograde transport of horseradish peroxidase from the visual cortex to the principal laminae of the lateral geniculate nucleus suggested that monocular deprivation from early in life may lead to a gross reduction in the distribution of afferent fibres from the deprived laminae. Previous experiments have found that if a kitten is exposed only to contours of one orientation, its cortical neurons become modified in their distribution of preferred orientations. This phenomenon was re-confirmed in a new study using a rigorously objective method of analysis.

The organization of somatosensory cortex in the short-tailed opossum ( Monodelphis domestica )

Abstract: The organization of neocortex in the short-tailed opossum ( Monodelphis domestica ) was explored with multiunit microelectrode recordings from middle layers of cortex. Microelectrode maps were subsequently related to the chemoarchitecture of flattened cortical preparations, sectioned parallel to the cortical surface and processed for either cytochrome oxidase (CO) or NADPH-diaphorase (NADPHd) histochemistry. The recordings revealed the presence of at least two systematic representations of the contralateral body surface located in a continuous strip of cortex running from the rhinal sulcus to the medial wall. The primary somatosensory area (S1) was located medially while secondary somatosensory cortex (S2) formed a laterally located mirror image of S1. Auditory cortex was located in lateral cortex at the caudal border of S2, and some electrode penetrations in this area responded to both auditory and somatosensory stimulation. Auditory cortex was outlined by a dark oval visible in flattened brain sections....