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Results for “cortical development”

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At least 1,261 records · Page 70Linked to original sources
PubMed1985

Electrophysiological and morphological correlates in the development of visual cortical circuitry in infant kittens.

Geniculate axons in cat visual cortex establish excitatory connections with cortical cells in supragranular and granular layers at birth. They are localized to the granular layer for the first month after birth. Retraction of geniculocortical synapses parallels axonal extension of spiny stellate cells to the supragranular layer and establishment of synapses for intracortical transmission.

Animals↗
PubMed1993

Transient expression of calbindin-D28k immunoreactivity in layer V pyramidal neurons during postnatal development of kitten cortical areas.

Calbindin-D28k is a 28 kDa calcium binding protein that has been shown to colocalize with a specific subpopulation of gamma-aminobutyric acid inhibitory interneurons in mammalian neocortex. We have examined the ontogeny of calbindin in neonatal kitten cortex in areas 17,18,19,7, medial and lateral suprasylvian visual areas, splenial visual area and cingulate cortex from the day of birth (P0) through maturation of the brain (P101). Transient staining of immature layer V pyramidal cells was seen in kittens six weeks old and younger. This transient staining of pyramidal cells was most intense and the stained neurons were most numerous in cingulate cortex. Apical dendrites of pyramidal cells in cingulate cortex were prominently stained and could be followed to layer I, where they were seen to branch extensively. There were very few calbindin immunoreactive pyramidal cells in primary cortical areas postnatally. Transient staining in extrastriate visual cortical areas disappeared first from the lateral suprasylvian areas, and persisted longest in area 7. Pyramidal neurons in the cingulate gyrus expressed calbindin longest, but calbindin expression by pyramidal neurons ceased by the sixth postnatal week in all areas of the brain.

Aging↗
PubMed1979

Development of visual cortical orientation specificity after dark-rearing: role of extraocular proprioception.

Six-week-old dark reared kittens exposed to light for 6 h: (1) with head and body tightly cast into plaster; or (2) free to move around in the animal room. A few days before the visual experience, the ophthalmic branch of the 5th nerve was severed bilaterally in experimental kittens, in order to suppress most of the proprioceptive afferents from extraocular muscles. Electrophysiological analysis of the properties of the receptive fields of visual cortical cells shows that only 6% (group 1) and 11% (group 2) of the cells were selective to orientation as opposed to 67% (group 1) or 32% (group 2) observed in the non-operated kittens.

Animals↗
PubMed2006

Language and cortical function: conceptual developments.

Mastery of a language is a capacity that distinguishes humans from other animals. Attempts to identify the brain functions that are necessary for the possession of linguistic skills began in the 19th century with the research of Broca and Wernicke. We trace the principal experimental developments since then, ranging from psychological studies of aphasic patients to non-invasive brain-imaging investigations. The development of theories concerning word recognition, reading aloud, fluent speech and understanding utterances are described. Possible brain regions involved in these abilities, identified by means of non-invasive imaging, are considered. We examine the various claims made by these researchers as to what their experiments show and in particular examine the validity of their theories. This conceptual analysis shows that in many cases the interpretation of experiments is confused and that the theories elaborated are not tenable. We seek to clarify what can be substantiated concerning the workings of the brain and the exercise of linguistic skills.

Aphasia↗
PubMed1998

A behavioral and immunohistochemical study on the development of perirhinal cortical kindling: a comparison with other types of limbic kindling.

We have previously reported that the perirhinal cortex (PRC) plays an important role in the generalization of kindled seizures. In the present study, we kindled the rat PRC and made a comparison with amygdala (AM) and dorsal hippocampal (dHIPP) kindling. In order to produce a functional map of the seizure generalization pathway from these limbic foci, we also stained for Fos protein in sections of the PRC-, AM- and dHIPP-kindled brains using an immunohistochemistry technique. In the generalized seizures of PRC kindling the duration of afterdischarges (ADs) and the latency to forelimb clonus were significantly shorter than those of AM kindling or dHIPP kindling. Typically, the PRC-kindled rats demonstrated moving arrest or exploratory behavior for about 10 days, and then a characteristic 'rapid backward moving' behavior for 1 day, followed by the sudden appearance of generalized motor seizures. Fos protein induction after a single stimulation of the PRC is more widely observed than after a single stimulation of the AM, in that the PRC stimulation produced Fos protein expression in the temporal and parietal neocortices. Following AM and PRC kindling, the Fos-positive areas were asymmetrically propagated from the ipsilateral to the contralateral hemisphere. The contralateral PRC was primarily activated at the generalization of epileptic activity in the contralateral hemisphere. In contrast, the Fos protein distribution of the dHIPP-kindled rats was restricted to the bilateral hippocampi during the early stages, followed by the symmetrical propagation from the limbic system to the neocortex during the generalized seizures. These results indicate that the PRC plays a characteristic role in the seizure generalization of kindling.

Amygdala↗
PubMed2005

Learning in ex-vivo developing networks of cortical neurons.

This contribution describes the use of multi-site interaction with large cortical networks in the study of learning. The general physiological properties of the network are described, and the concept of learning is mapped to the experimental network preparation. Learning is then analyzed in terms of exploration (defined as changes in the configuration of associations within the biological network) and recognition (the stabilization of "worthy" associations).

Animals↗
PubMed1997

Agrin gene expression in mouse somatosensory cortical neurons during development in vivo and in cell culture.

Agrin is an extracellular matrix protein involved in the formation of the postsynaptic apparatus of the neuromuscular junction. In addition to spinal motor neurons, agrin is expressed by many other neuronal populations throughout the nervous system. Agrin's role outside of the neuromuscular junction, however, is poorly understood. Here we use the polymerase chain reaction to examine expression and alternative splicing of agrin in mouse somatosensory cortex during early postnatal development in vivo and in dissociated cell culture. Peak levels of agrin gene expression in developing cortex coincide with ingrowth of thalamic afferent fibres and formation of thalamocortical and intracortical synapses. Analysis of alternatively spliced agrin messenger RNA variants shows that greater than 95% of all agrin in developing and adult somatosensory cortex originates in neurons, including isoforms that have little or no activity in acetylcholine receptor aggregation assays. The levels of expression of "active" and "inactive" isoforms, however, are regulated during development. A similar pattern of agrin gene expression is also observed during a period when new synapses are being formed between somatosensory neurons growing in dissociated cell culture. Changes in agrin gene expression, observed both in vivo and in vitro, are consistent with a role for agrin in synapse formation in the central nervous system.

2-Amino-5-phosphonovalerate↗
PubMed1989

Frequency of development of early cortical scarring in acute primary pyelonephritis.

Fifty-five cases of primary (that is, without urinary tract abnormalities), acute pyelonephritis (PN) were studied by computed tomodensitometry (CT). There were 48 women and 7 men. All were febrile and 16 had positive blood cultures. In 7 cases, (4 diabetics and 3 malnourished alcoholics) PN was painless, diagnosis was delayed and lesions were severe. Two diabetics underwent emergency nephrectomy for sepsis. Conventional radiological techniques (IVP and ultrasonography) were poorly informative. In contrast, initial CT abnormalities were visible in 44 patients. They consisted of triangular or round hypodense images, diffuse hypodensity in a grossly swollen kidney, and/or abscesses. Hypodense images were presumably due to acute focal ischemia. Renal histology was available in five patients. It showed acute interstitial nephritis with leukocyte infiltrates, edema and hemorrhagic streaks. Pyelonephritis was due to E. coli in 48 cases (87.5%). In 27 cases E. coli isolates were studied by genotypic assays which detect the three most frequent (pap, afa and sfa) of the four operons known to encode adhesin. In all cases, at least one of these genotypic markers of uropathogenicity was found. In 27 cases, repeat CT was done shortly after treatment. It showed healing in only 12. Early cortical scar formation was visible in 2. Final evaluation in 27 cases with adequate follow-up showed that (in addition to the 2 patients who had been nephrectomized), in only 17 of 27 (63%) had the kidneys recovered a normal appearance. In two cases one kidney had undergone atrophy; renal biopsy showed subacute-chronic interstitial nephritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1981

Inhibitory circuits accounting for development of visual cortical mappings, stimulus preferences, and psychophysical performance.

A developmental rationale is proposed for the circuitry underlying the generation of fine retinotopic mappings, the quantitative range of simple-cell stimulus preferences, and the psychophysical performance of the visual system. It is assumed that the retina consists of a mosaic of partially overlapping elements, or hyperfields, which are laid down in a sunflower-seed pattern. These hyperfields project to a corresponding rectilinear mosaic of hypercolumns in the cortex, according to a pattern of chemoaffinities. Each hyperfield, in turn, consists of a sunflower-seed mosaic of nonoverlapping ganglion-cell receptive-field centres, which project to a matching rectilinear mosaic of minicolumns in the corresponding hypercolumn. Retinotopic order is produced in the hyperfield-hypercolumn mapping by radially symmetric inhibitory links, between cortical cells more than two minicolumns apart, which operate on Hebb-modifiable retinocortical excitatory afferent fibres. Under this mapping, hyperfield radii map onto parallel rows of minicolumns (orientation columns), and concentric semicircles of ganglion-cell receptive fields map onto spatial-frequency columns, crossing orientation columns at right angles. The 'scatter' in this mapping is equivalent to one local average receptive-field diameter. Orientation-related stimulus preferences ar produced by asymmetrical inhibitory links between cells more than two minicolumns apart, in the same spatial-frequency columns. A third network of inhibitory circuits, with Hebb-modifiable synapses, is assumed to operate between cells in the same or immediately adjacent minicolumns. This network enhances stimulus selectivity and sensitivity in simple and hypercomplex cells, and is responsible for adaptation aftereffects and sensory information storage.

Adaptation, Ocular↗