scholarly journals Analysis of an Experimental Cortical Network: i) Architectonics of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid; Similarities with Human Microgyria

1991 ◽  
Vol 2 (1) ◽  
pp. 1-28 ◽  
Author(s):  
G. M. Innocenti ◽  
P. Berbel
Keyword(s):  
Radial Glia ◽  
Thick Layer ◽  
Ibotenic Acid ◽  
Cortical Areas ◽  
Visual Areas ◽  
Local Injections ◽  
Layer I ◽  
Areas 17 And 18 ◽  
Normal Cortex ◽  
Severe Destruction

Lesions of cortical areas 17 and 18 have been produced in newborn kittens by local injections of the excitotoxin ibotenic acid (ibo). Twenty-four hours after an injection on postnatal days 2 or 3, the gray matter of areas 17 and 18 near the center of the injection appears completely destroyed, with the exception of a one-to-two cell-thick layer at the bottom of layer I. Intact migrating neurons and radial glia can be found light- and electron-microscopically in the region affected. During the following weeks a several hundred micron thick cortex reforms. In the adult, this cortex consists of superficial layers I, II and III as proven by cytoarchitectonics, continuity with the corresponding layers of the normal cortex and cellular composition. We believe that the recovery is due to completion of migration by neurons spared by the ibo injection. More severe destruction of cerebral cortex, i.e. complete loss of the neuronal layers or their reduction to a few cell-thick mantles can be obtained with ibo injections at the end of the second or, respectively, first postnatal week. Severity of lesion also depends on the dose of ibo injected. There are interesting similarities between the ibo-injured cortex and two human neocortical displasias: microgyria and ulegyria.

scholarly journals Analysis of an Experimental Cortical Network: ii) Connections of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid

1991 ◽  
Vol 2 (1) ◽  
pp. 29-54 ◽  
Author(s):  
G. M. Innocenti ◽  
P. Berbel
Keyword(s):  
Horseradish Peroxidase ◽  
Corpus Callosum ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Ibotenic Acid ◽  
Contralateral Hemisphere ◽  
Cortical Areas ◽  
Visual Areas ◽  
Local Injections ◽  
Areas 17 And 18

Lesions of cortical areas 17 and 18 were produced in newborn kittens by local injections of the excitotoxin ibotenic acid. In the adult this results in a microcortex which consists of superficial layers I, II and III, in the absence of granular and infragranular layers. Horseradish peroxidase, alone or wheat germ agglutinin conjugated, was injected in the microcortex or in the contralateral, intact areas 17 and 18. The microcortex maintains several connections characteristic of normal areas 17 and 18 of the cat. It receives afferents from the dLGN, and several visual areas of the ipsilateral and contralateral hemisphere. However, it has lost its projections to dLGN, superior colliculus, and, at least in part, those to contralateral visual areas. Thus some parts of the microcortex receive from, but do not project into, the corpus callosum. In addition, the microcortex maintains afferents from ipsilateral and contralateral auditory areas AI and AII which are normally eliminated in development.

First order connections of the visual sector of the thalamic reticular nucleus in marmoset monkeys (Callithrix jacchus)

2007 ◽  
Vol 24 (6) ◽  
pp. 857-874 ◽  
Author(s):  
THOMAS FITZGIBBON ◽  
BRETT A. SZMAJDA ◽  
PAUL R. MARTIN
Keyword(s):  
Visual Field ◽  
Callithrix Jacchus ◽  
Higher Order ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Lower Visual Field ◽  
First Order ◽  
Cortical Areas ◽  
Visual Areas

The thalamic reticular nucleus (TRN) supplies an important inhibitory input to the dorsal thalamus. Previous studies in non-primate mammals have suggested that the visual sector of the TRN has a lateral division, which has connections with first-order (primary) sensory thalamic and cortical areas, and a medial division, which has connections with higher-order (association) thalamic and cortical areas. However, the question whether the primate TRN is segregated in the same manner is controversial. Here, we investigated the connections of the TRN in a New World primate, the marmoset (Callithrix jacchus). The topography of labeled cells and terminals was analyzed following iontophoretic injections of tracers into the primary visual cortex (V1) or the dorsal lateral geniculate nucleus (LGNd). The results show that rostroventral TRN, adjacent to the LGNd, is primarily connected with primary visual areas, while the most caudal parts of the TRN are associated with higher order visual thalamic areas. A small region of the TRN near the caudal pole of the LGNd (foveal representation) contains connections where first (lateral TRN) and higher order visual areas (medial TRN) overlap. Reciprocal connections between LGNd and TRN are topographically organized, so that a series of rostrocaudal injections within the LGNd labeled cells and terminals in the TRN in a pattern shaped like rostrocaudal overlapping “fish scales.” We propose that the dorsal areas of the TRN, adjacent to the top of the LGNd, represent the lower visual field (connected with medial LGNd), and the more ventral parts of the TRN contain a map representing the upper visual field (connected with lateral LGNd).

Structural basis of cortical synchronization. II. Effects of cortical lesions

1995 ◽  
Vol 74 (6) ◽  
pp. 2401-2414 ◽  
Author(s):  
M. H. Munk ◽  
L. G. Nowak ◽  
J. I. Nelson ◽  
J. Bullier
Keyword(s):  
Corpus Callosum ◽  
Posterior Part ◽  
Preceding Paper ◽  
Ibotenic Acid ◽  
Border Region ◽  
Extrastriate Cortex ◽  
Structural Basis ◽  
Encounter Rate ◽  
Cortical Areas ◽  
Reciprocal Connections

1. To understand the structural basis of the different types of interhemispheric synchronizations described in the preceding paper, we made sections of the corpus callosum and lesions of extrastriate cortex. We measured the effects of such operations on the frequency of encounter, width and strength of T, C, and H peaks in cross-correlation histograms computed from single-unit and multiunit recordings from areas 17-18 of opposite cortical hemispheres in the cat. 2. Sectioning of the corpus callosum led to a complete abolition of T and C couplings and a strong reduction of encounter rate and strength of H coupling. A section limited to the posterior half of the corpus callosum abolished T and C couplings completely. This suggests that T and C couplings are mediated by the direct reciprocal connections between visual cortical areas circulating through the posterior part of the corpus callosum. 3. The encounter rate of H peaks depended on the extent of the callosal cut. Larger lesions gave a more pronounced reduction of the number of H peaks. From this observation we conclude that H peaks are at least partially mediated by polysynaptic pathways involving widely distributed cortical regions. 4. Extensive lesions of extrastriate cortex were made by aspiration of the gray matter or injections of ibotenic acid. These lesions removed the direct inputs from cortical areas sending ipsilateral as well as contralateral inputs to the area 17-18 border region. Encounter rate and coupling strength of C and H peaks were decreased, whereas little effect was observed on T peaks. 5. These results demonstrate that all types of interhemispheric synchronization are mediated by corticocortical connections and that T and C peaks are generated by reciprocal connections between areas 17 and 18 of each hemisphere. Feedback connections play a role in mediating or facilitating the C and H types of interhemispheric synchronization.

An examination of linking hypotheses drawn from the perceptual consequences of experimentally induced changes in neural circuitry

2013 ◽  
Vol 30 (5-6) ◽  
pp. 271-276 ◽  
Author(s):  
DONALD E. MITCHELL ◽  
STEPHEN G. LOMBER
Keyword(s):  
Striate Cortex ◽  
Extended Period ◽  
Monocular Deprivation ◽  
Specific Cell ◽  
Cortical Areas ◽  
Good Spatial Resolution ◽  
Areas 17 And 18 ◽  
Visual Cortical ◽  
Areas Of Interest ◽  
Induced Changes

AbstractBecause targeted early experiential manipulations alter both perception and the response properties of particular cells in the striate cortex, they have been used as evidence for linking hypotheses between the two. However, such hypotheses assume that the effects of the early biased visual input are restricted to just the specific cell population and/or visual areas of interest and that the neural populations that contribute to the visual perception itself do not change. To examine this assumption, we measured the consequences for vision of an extended period of early monocular deprivation (MD) on a kitten (from 19 to 219 days of age) that began well before, and extended beyond, bilateral ablation of visual cortical areas 17 and 18 at 132 days of age. In agreement with previous work, the lesion reduced visual acuity by only a factor of two indicating that the neural sites, other than cortical areas 17 and 18, that support vision in their absence have good spatial resolution. However, these sites appear to be affected profoundly by MD as the effects on vision were just as severe as those observed following MD imposed on normal animals. The pervasive effects of selected early visual deprivation across many cortical areas reported here and elsewhere, together with the potential for perception to be mediated at a different neural site following deprivation than after typical rearing, points to a need for caution in the use of data from early experiential manipulations for formulation of linking hypotheses.

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

2006 ◽  
Vol 95 (5) ◽  
pp. 2768-2786 ◽  
Author(s):  
Takahisa M. Sanada ◽  
Izumi Ohzawa
Keyword(s):  
Alternative Hypothesis ◽  
Three Dimensional ◽  
Correlation Technique ◽  
Three Dimensional Objects ◽  
Spatial Pooling ◽  
Surface Slant ◽  
Visual Areas ◽  
Early Visual Cortex ◽  
Areas 17 And 18 ◽  
Electrophysiological Methods

How are surface orientations of three-dimensional objects and scenes represented in the visual system? We have examined an idea that these surface orientations are encoded by neurons with a variety of tilts in their binocular receptive field (RF) structure. To examine whether neurons in the early visual areas are capable of encoding surface orientations, we have recorded from single neurons extracellularly in areas 17 and 18 of the cat using standard electrophysiological methods. Binocular RF structures are obtained using a binocular version of the reverse correlation technique. About 30% of binocularly responsive neurons have RFs with statistically significant tilts from the frontoparallel plane. The degree of tilts is sufficient for representing the range of surface slants found in typical visual environments. For a subset of neurons having significant RF tilts, the degrees of tilt are correlated with the preferred spatial frequency difference between the two eyes, indicating that a modified disparity energy model can account for the selectivity, at least partially. However, not all cases could be explained by this model, suggesting that multiple mechanisms may be responsible. Therefore an alternative hypothesis is also examined, where the tilt is generated by pooling of multiple disparity detectors whose preferred disparities progressively shift over space. Although there is evidence for extensive spatial pooling, this hypothesis was not satisfactory either, in that the neurons with extensive pooling tended to prefer an untilted surface. Our results suggest that encoding of surface orientations may begin with the binocular neurons in the early visual cortex.

Topographic organization, number, and laminar distribution of callosal cells connecting visual cortical areas 17 and 18 of normally pigmented and Siamese cats

1992 ◽  
Vol 9 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Nancy E. J. Berman ◽  
Simon Grant
Keyword(s):  
Pyramidal Neurons ◽  
Area 17 ◽  
Vertical Meridian ◽  
Cortical Areas ◽  
Area Centralis ◽  
Areas 17 And 18 ◽  
Contralateral Eye ◽  
Visual Cortical ◽  
Callosal Pathway ◽  
Cell Zone

AbstractThe callosal connections between visual cortical areas 17 and 18 in adult normally pigmented and “Boston” Siamese cats were studied using degeneration methods, and by transport of WGA-HRP combined with electrophysiological mapping. In normal cats, over 90% of callosal neurons were located in the supragranular layers. The supragranular callosal cell zone spanned the area 17/18 border and extended, on average, some 2–3 mm into both areas to occupy a territory which was roughly co-extensive with the distribution of callosal terminations in these areas. The region of the visual field adjoining the vertical meridian that was represented by neurons in the supragranular callosal cell zone was shown to increase systematically with decreasing visual elevation. Thus, close to the area centralis, receptive-field centers recorded from within this zone extended only up to 5 deg into the contralateral hemifield but at elevations of -10 deg and -40 deg they extended as far as 8 deg and 14 deg, respectively, into this hemifield. This suggests an element of visual non-correspondence in the callosal pathway between these cortical areas, which may be an essential substrate for “coarse” stereopsis at the visual midline.In the Siamese cats, the callosal cell and termination zones in areas 17 and 18 were expanded in width compared to the normal animals, but the major components were less robust. The area 17/18 border was often devoid of callosal axons and, in particular, the number of supragranular layer neurons participating in the pathway were drastically reduced, to only about 25% of those found in the normally pigmented adults. The callosal zones contained representations of the contralateral and ipsilateral hemifields that were roughly mirror-symmetric about the vertical meridian, and both hemifield representations increased with decreasing visual elevation. The extent and severity of the anomalies observed were similar across individual cats, regardless of whether a strabismus was also present. The callosal pathway between these visual cortical areas in the Siamese cat has been considered “silent,” since nearly all neurons within its territory are activated only by the contralateral eye. The paucity of supragranular pyramidal neurons involved in the pathway may explain this silence.

scholarly journals A Dissociation of Attention and Awareness in Phase-sensitive but Not Phase-insensitive Visual Channels

2010 ◽  
Vol 22 (10) ◽  
pp. 2326-2344 ◽  
Author(s):  
Jan W. Brascamp ◽  
Jeroen J. A. van Boxtel ◽  
Tomas H. J. Knapen ◽  
Randolph Blake
Keyword(s):  
Selective Attention ◽  
Visual Awareness ◽  
Scientific Study ◽  
Conscious Awareness ◽  
Neural Processing ◽  
Cortical Areas ◽  
Visual Areas ◽  
Response Enhancement ◽  
Early Processing ◽  
Phase Sensitive

The elements most vivid in our conscious awareness are the ones to which we direct our attention. Scientific study confirms the impression of a close bond between selective attention and visual awareness, yet the nature of this association remains elusive. Using visual afterimages as an index, we investigate neural processing of stimuli as they enter awareness and as they become the object of attention. We find evidence of response enhancement accompanying both attention and awareness, both in the phase-sensitive neural channels characteristic of early processing stages and in the phase-insensitive channels typical of higher cortical areas. The effects of attention and awareness on phase-insensitive responses are positively correlated, but in the same experiments, we observe no correlation between the effects on phase-sensitive responses. This indicates independent signatures of attention and awareness in early visual areas yet a convergence of their effects at more advanced processing stages.

scholarly journals Mechanisms of Plasticity in Subcortical Visual Areas

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 3162
Author(s):  
Maël Duménieu ◽  
Béatrice Marquèze-Pouey ◽  
Michaël Russier ◽  
Dominique Debanne
Keyword(s):  
Neuronal Plasticity ◽  
Visual Information ◽  
Molecular Mechanisms ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Body Movements ◽  
Cortical Areas ◽  
Visual Areas ◽  
Dorsal Lateral Geniculate ◽  
Activity Dependent ◽  
Mechanisms Of Plasticity

Visual plasticity is classically considered to occur essentially in the primary and secondary cortical areas. Subcortical visual areas such as the dorsal lateral geniculate nucleus (dLGN) or the superior colliculus (SC) have long been held as basic structures responsible for a stable and defined function. In this model, the dLGN was considered as a relay of visual information travelling from the retina to cortical areas and the SC as a sensory integrator orienting body movements towards visual targets. However, recent findings suggest that both dLGN and SC neurons express functional plasticity, adding unexplored layers of complexity to their previously attributed functions. The existence of neuronal plasticity at the level of visual subcortical areas redefines our approach of the visual system. The aim of this paper is therefore to review the cellular and molecular mechanisms for activity-dependent plasticity of both synaptic transmission and cellular properties in subcortical visual areas.

scholarly journals Biological variation in the sizes, shapes and locations of visual cortical areas in the mouse

2018 ◽  
Author(s):  
Jack Waters ◽  
Eric Lee ◽  
Nathalie Gaudreault ◽  
Fiona Griffin ◽  
Jerome Lecoq ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Information ◽  
Biological Variation ◽  
Measurement Noise ◽  
Cortical Areas ◽  
Retinotopic Maps ◽  
Visual Areas ◽  
Visual Cortical ◽  
Cortical Visual Areas ◽  
Processing Of Visual Information

ABSTRACTVisual cortex is organized into discrete sub-regions or areas that are arranged into a hierarchy and serve different functions in the processing of visual information. In our previous work, we noted that retinotopic maps of cortical visual areas differed between mice, but did not quantify these differences or determine the relative contributions of biological variation and measurement noise. Here we quantify the biological variation in the size, shape and locations of 11 visual areas in the mouse. We find that there is substantial biological variation in the sizes of visual areas, with some visual areas varying in size by two-fold across the population of mice.

Sign in / Sign up

Export Citation Format

Share Document