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At least 163 records · Page 9Linked to original sources
PubMed1970

Mescaline-induced changes of brain-cortex ribosomes. Effect of mescaline on the hydrogen-bonded structure of ribonucleic acid of brain-cortex ribosomes.

1. The action of mescaline sulphate on the hydrogen-bonded structure of the RNA constituent of ribosomes of goat brain-cortex slices was studied by using the hyperchromic effect of heating and formaldehyde reaction. 2. The ribosomal total RNA species of the mescaline-treated brain-cortex slices have a smaller proportion of hydrogen-bonded structure than the ribosomal RNA species of the untreated brain-cortex slices. 3. Mescaline also appears to have affected this lowering of hydrogen-bonded structure of the ribosomal 28S RNA of brain-cortex tissue.

Animals↗
PubMed1993

Monocular deprivation effects in the rat visual cortex and lateral geniculate nucleus are prevented by nerve growth factor (NGF). I. Visual cortex.

The effects of monocular deprivation done during the critical period are usually ascribed to competition between the two sets of monocular thalamic afferents taking place at cortical level. We have suggested that loss in competition for the deprived eye is explained by the lack of a neurotrophic factor, produced in the cortex and dependent on electrical activity. To test this hypothesis we have exogenously supplied nerve growth factor (NGF) to rats monocularly deprived (MD) during the critical period, and studied whether monocular deprivation still affected the functional and anatomical organization of the visual cortex. NGF is produced in the rat visual cortex during the critical period, and its expression, at least in the hippocampus, seems to be regulated by electrical activity. Ocular dominance distribution of area 17 neurons, visual acuity, and Parvalbumin immunoreactivity (Parva-LI) were determined in four sets of animals: normal rats, control untreated monocularly deprived rats, deprived rats treated with cytochrome c (to control for non-specific aspects of NGF treatment), and deprived rats treated with NGF. Parva-LI is an excellent marker for the effects of monocular deprivation on the functional organization of the rat visual cortex. We found that exogenous supply of NGF completely prevented the shift in ocular dominance distribution of visual cortical neurons, the loss of visual acuity for the deprived eye, and the strong reduction in Parva-LI induced by monocular deprivation in control rats.

Acetylcholinesterase↗
PubMed1999

How does the cerebral cortex work? Learning, attention, and grouping by the laminar circuits of visual cortex.

The organization of neocortex into layers is one of its most salient anatomical features. These layers include circuits that form functional columns in cortical maps. A major unsolved problem concerns how bottom-up, top-down, and horizontal interactions are organized within cortical layers to generate adaptive behaviors. This article models how these interactions help visual cortex to realize: (i) the binding process whereby cortex groups distributed data into coherent object representations; (ii) the attentional process whereby cortex selectively processes important events; and (iii) the developmental and learning processes whereby cortex shapes its circuits to match environmental constraints. New computational ideas about feedback systems suggest how neocortex develops and learns in a stable way, and why top-down attention requires converging bottom-up inputs to fully activate cortical cells, whereas perceptual groupings do not.

Attention↗
PubMed2000

[Treatment of central and neuropathic facial pain by chronic stimulation of the motor cortex: value of neuronavigation guidance systems for the localization of the motor cortex].

Thirty two patients with refractory central and neuropathic pain of peripheral origin were treated by chronic stimulation of the motor cortex between May 1993 and January 1997. The mean follow-up was 27. 3 months. The first 24 patients were operated according to the technique described by Tsubokawa. The last 13 cases (8 new patients and 5 reinterventions) were operated by a technique including localization by superficial CT reconstruction of the central region and neuronavigator guidance. The position of the central sulcus was confirmed by the use of intraoperative somatosensory evoked potentials. The somatotopic organisation of the motor cortex was established peroperatively by studying the motor responses at stimulation of the motor cortex through the dura. Ten of the 13 patients with central pain (77%) and nine of the 12 patients with neuropathic facial pain had experienced substantial pain relief (75%). One of the 3 patients with post-paraplegia pain was clearly improved. A satisfactory result was obtained in one patient with pain related to plexus avulsion and in one patient with pain related to intercostal herpes zoster. None of the patients developed epileptic seizures. The position of the stimulating poles effective on pain corresponded to the somatotopic representation of the motor cortex. The neuronavigator localization and guidance technique proved to be most useful identifying the appropriate portion of the motor gyrus. It also allowed the establishment of reliable correlations between electrophysiological-clinical and anatomical data which may be used to improve the clinical results and possibly to extend the indications of this technique.

Adult↗
PubMedDate not supplied

[Protein synthesis in cerebral cortex cells of rats exposed to hypoxia during interparenchymal administration of protein isolated from embryonal nerve tissue into the cerebral cortex].

The stage-specific activator protein CF was studied for effects on protein biosynthesis in the fractions rich in nerve and glial cells of the brain cortex of rats which had been exposed to hypoxia. Protein was isolated from the cortex of embryos or from the cerebellum of 8-10-day rats, the period being of the most active nerve cell proliferation. Following 4 days of the interparenchymal administration of SF into the cerebral cortex of the animals exposed to hypoxia there was an increase in the rate of 3-H-leucine incorporation into the nerve cells up to the values observed in the neurons of the cerebral cortex of intact animals. The level of protein synthesis in the glial cells remained unchanged. There were no increases in protein synthesis either in nerve or glial cells 120 days after single administration of SF. The findings were compared with the experimental evidence for the biosynthesis of macromolecules in various cerebral cortical cells from rats exposed to hypoxia and undergone transplantation of embryonal nerve tissue.

Animals↗
PubMed1988

Cotransplantation of embryonic mouse retina with tectum, diencephalon, or cortex to neonatal rat cortex.

Retinae from embryonic mice were transplanted to the occipital cortex of neonatal rats together with their normal target regions, tectum or diencephalon, from embryonic mice or rats. In control experiments, retinae were cotransplanted with embryonic rat occipital cortex. In over 80% of the experimental animals, both transplants differentiated and grew. Ganglion cells in the retinae cotransplanted close to tectum or diencephalon survived for at least 15 weeks. Their survival was associated with the development of a distinct optic fiber layer and outgrowth of axons from the transplanted mouse retina. Specific innervation of distinct patches within the cotransplanted rat tectum or diencephalon was demonstrated by the use of an anti-mouse antibody. The innervated regions, which could be as far away as 1.3 mm from the retinae, were correlated with cytological features of the cotransplanted tectum or diencephalon. By contrast, the host cortex was never innervated by the transplanted retinae. In the control animals in which the retinae were cotransplanted with occipital cortex and in four animals in which the cotransplants lay more than 2.7 mm apart, no ganglion cells were identified and there was no evidence of an optic fiber layer, outgrowth of axons, or innervation. These results support the idea that in order to survive, retinal ganglion cells need to innervate an appropriate target region. Further, the specific innervation of regions within the cotransplanted tectum or diencephalon suggests that these target regions are able to exert a tropic influence on the axons of retinal ganglion cells, even in the absence of many of the normal structure cues.

Animals↗
PubMed1987

Relation of olfactory bulb and cortex. II. Model for driving of cortex by bulb.

The major projection pathway of the olfactory bulb is by way of the lateral olfactory tract (LOT) to the olfactory cortex. Oscillatory bursts of extracellular potential appear during inspiration in both bulb and cortex. Based on anatomical and physiological considerations, a model was proposed, consisting of a bulbar transmitter, a conduction line representing axons in the LOT, and a cortical receiver. The model predicted the relation between phase and frequency of bulbar and cortical burst pairs, based on the expectation that the bulb drives the cortex. Experimental phase-frequency plots were computed from bursts of 9 bulbocortical electrode site pairs from each of 10 rabbits. For each site pair, the model predicted the expected range of the joint variation of phase and frequency, using the known distance between the bulbar and cortical sites. The model was highly successful (greater than 95% prediction accuracy) for one quarter of the total number of site pairs examined. The wide range of variation for the rest of the data suggested that higher order interactions are responsible for the phase relation between bulb and cortex. Convergence of input, independence of the cortical generator, cortical feedback to the bulb and synchronization by an outside source are all discussed as possible contributors to this variation.

Animals↗
PubMed1988

Intraventricular administration of the cholinotoxin AF64A increases the accumulation of aluminum in the rat parietal cortex and hippocampus, but not in the frontal cortex.

Aluminum (Al) concentrations of the rat frontal cortex, parietal cortex, and hippocampus were measured by atomic absorption spectroscopy 16 days after a unilateral intracerebroventricular injection of Na gluconate, Al gluconate, or the cholinotoxin AF64A. A fourth group of rats were injected with AF64A 6 days before injection of Al gluconate and subsequently sacrificed 10 days later. The combined treatment of AF64A and Al gluconate resulted in enhanced intraneuronal accumulation of Al in the parietal cortex and hippocampus but not in the frontal cortex. Consequently, Al may not be considered to be a primary factor in the pathogenesis of Alzheimer's disease.

Aluminum↗
PubMed1992

Electrophysiological influences of the parietal cortex and dorso-medial thalamic nucleus on the prefrontal cortex of the cat.

Lesion studies have shown that the functional integrity of prefrontal and posterior parietal cortex is necessary for complex behavioural performance. Recordings were made from 137 prefrontal cells in awake cats. Parietal cortex stimulation affected fifty-four cells (39.5%); thirty-four (63%) increased and twenty (37%) decreased their discharge frequency. Thalamic stimulation affected forty-seven cells; twenty-eight increased their discharge and nineteen decreased it. These responses suggest firstly that the organization between parietal and prefrontal cortex is similar to that in monkeys, and secondly that prefrontal cortex has an integrative role.

Animals↗
PubMed2002

Interaction of inferior temporal cortex with frontal cortex and basal forebrain: double dissociation in strategy implementation and associative learning.

Macaque monkeys learned a strategy task in which two groups of visual objects needed to be treated differently, one with persistent and one with sporadic object choices, to obtain food rewards. After preoperative training, they were divided into two surgical groups of three monkeys each. One group received crossed unilateral removals of frontal cortex and inferior temporal cortex (IT x FC) and were severely impaired in performing the strategy task. The other group received bilateral transection of anterior temporal stem, amygdala, and fornix (TS+AM+FX) and were unimpaired in performing the strategy task. Subsequently the same animals were tested in visual object-reward association learning. Here, confirming previous results, group IT x FC was unimpaired, whereas group TS+AM+FX was severely impaired. The results show that the amnesic effects of TS+AM+FX cannot be generally attributed to the partial temporal-frontal disconnection that this lesion creates, and therefore support the hypothesis that the amnesic effects of this lesion are caused primarily by the disconnection of temporal cortex from ascending inputs from the basal forebrain. The results also show that temporal-frontal interaction in strategy implementation does not require those routes of temporal-frontal interaction that are interrupted in TS+AM+FX, and therefore support the hypothesis that projections to other posterior cortical areas allow temporal and frontal cortex to interact with each other by multisynaptic corticocortical routes in strategy implementation.

Amygdala↗
PubMed2000

Is there an optimal age for recovery from motor cortex lesions? II. behavioural and anatomical consequences of unilateral motor cortex lesions in perinatal, infant, and adult rats.

Purpose: The purpose of this study was to compare the behavioural and anatomical effects of unilateral motor cortex ablation in neonatal, infant, and adult rats. Methods: Rats were given unilateral lesions of the motor cortex on the day of birth (P1), at ten days of age (P10), or in adulthood. They were trained on several motor tasks (skilled forelimb reaching, beam traversing, tongue extension), general motor activity, and a test of spatial learning (Morris water task). Results: Although all lesion groups were equally impaired at skilled reaching with the forelimb contralateral to the lesion, rats with P1 lesions also were impaired at traversing a narrow beam and at learning the Morris task. Gross anatomical analyses revealed that the P1 rats had smaller brains than the other groups, a result that may account for the larger behavioural deficits in the P1 group. Analysis of Golgi-Cox stained neurons showed that relative to control groups, all lesion groups showed an increase in dendritic length in the basilar dendrites of layer III pyramidal cells and, paradoxically a decrease in length of the apical dendrites of the same cells. Conclusions: The bilateral alterations in dendritic organization following the motor cortex lesions suggest that there has been a bilateral reor-ganization of intrinsic cortical connectivity following motor cortex lesions at any age. These alterations in connectivity are likely not identical in the young and adult animals, however, because relative to controls, both the young operated groups, but not the adult group, showed a bilat-eral drop in spine density in the basilar dendrites of layer V pyramidal cells. These findings are discussed with respect to the idea that there may be critical ages in development in which animals can use anatomical modifications to compensate for deficits produced by cortical injury.

Journal Article↗
PubMed1987

Long-lasting potentiation of synaptic potentials in the motor cortex produced by stimulation of the sensory cortex in the cat: a basis of motor learning.

A long-lasting increase in the efficiency of synaptic transmission in the central nervous system has been thought to be one of the bases of learning and memory. To explore the possibility that the motor cortex (area 4 gamma) itself is involved in motor learning, the existence of long-term potentiation (LTP) was examined by recording excitatory postsynaptic potentials (EPSPs) from motor cortical neurons. Short tetanic intracortical microstimulation (ICMS) of the somatic sensory cortex produced a marked potentiation of the EPSPs in a small group of motor cortical neurons. The results raised the possibility that the input from the sensory cortex participates in motor learning and retention of the learned motor skills.

Animals↗
PubMed1993

Monoamine concentrations in rat prefrontal cortex and other mesolimbocortical structures in response to partial neonatal lesions of the medial prefrontal cortex.

In an earlier study it was found that partial neonatal lesions of the medial prefrontal cortex (mPFC) resulted in an increased dopaminergic innervation in the remaining part of mPFC along with functional sparing. The present study assessed whether this response is restricted to this part of the cortex or whether also other structures of the mesolimbocortical system are involved. Furthermore, it was investigated whether the other monoaminergic systems were affected by neonatal mPFC lesions. In 6-day-old rats, the mPFC was partially ablated or a sham operation was made. The concentrations of dopamine (DA) and its metabolites increased to 250-350% in the remaining part of the mPFC compared to the sham-operated controls. The response was most prominent in this part of the cortex; no other mesolimbocortical structure showed such major changes of DA and its metabolites. In addition, a small increase in the concentrations of noradrenaline, serotonin and their metabolites was also spotted in the remaining mPFC and some other mesolimbocortical structures of the lesioned animals. The present data support the suggested involvement of DA in the neural mechanism of sparing of function, and this DA response seems to be most prominent in the remaining mPFC. However, the responses of the noradrenergic and serotonergic systems may also be important for sparing of function to occur.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Normal development of tyrosine hydroxylase and serotonin immunoreactive fibers innervating anterior cingulate cortex and visual cortex in rabbits exposed prenatally to cocaine.

Anterior cingulate cortex develops abnormally in rabbits exposed to cocaine in utero but visual cortex is normal. The interactions of cocaine with the dopamine, norepinephrine and serotonin systems makes each a potential candidate for influencing these developmental effects. Here, we report no differences in the distribution and density of serotonin and tyrosine hydroxylase-immunoreactive fibers in the anterior cingulate cortex in postnatal rabbits exposed prenatally to cocaine or saline. Because the pattern and extent of cortical innervation by these systems appears normal, the data suggest that the effects of prenatal exposure to cocaine may involve changes in monoamine signaling distinct from morphological reorganization of the cortical afferents.

Animals↗
PubMed1998

Neonatal lesion of the rat's frontal cortex and subsequent transplantation of embryonic frontal cortex: evidence of appropriate synaptic integration of the graft neurons within the host thalamo-fronto-striate circuit.

Previous observations in intact rats have indicated that axons from the ventrolateral thalamic nucleus (VL) establish direct axo-somatic or axo-dendritic contacts onto frontal cortical neurons projecting to the striatum. The embryonic frontal cortex was grafted into the damaged frontal cortex of newborn rats to study the capacity of homotopic transplants to restore the thalamo-fronto-striate pathway. Several months later, grafted neurons projecting to the striatum were identified by injecting a retrograde neurotracer (subunit b of the cholera toxin) into the ipsilateral caudate putamen. In the same animal, axons and terminations from the VL were labeled within the transplant with an anterograde neurotracer (Phaseolus vulgaris leuco-agglutinin) injected into the ipsilateral VL. The findings show that VL axons establish direct synaptic contacts onto grafted neurons projecting to the striatum. Although the synaptic contacts were scarce in the transplants, their organization was similar to that observed in intact rats. The contacts were axo-somatic or axo-dendritic. Our observations for the first time indicate that synaptic contacts are formed in cortical grafts and that fetal frontal cortex is susceptible to develop appropriate synaptic integration within the host thalamo-fronto-striate system.

Animals↗
PubMed1987

Effects of early environments on monkey cortex neuroanatomical changes following somatomotor experience: effects on layer III pyramidal cells in monkey cortex.

Sixteen infant stumptail monkeys were reared to 6 months under four conditions. Behaviors and cortical neuroanatomy were compared. Earlier studies showed effects on stellate cell dendrites. Here are reported the results in six cortical areas on basilar dendrites of layer III pyramidal cells. Basilar dendrites show significantly larger numbers (p less than .05) of branching for motor I cortex under condition 3 associated with the greatest skills and amount of activity in climbing, swinging, and grasping of objects. Visual cortex was not significantly altered by the rearing conditions, but the basilar dendrites showed less branching than in the five other areas of cortex sampled. It is concluded that genetic factors are responsible for the major growth patterns and that environmental factors contribute to quantitative increases or decreases in the branching of dendrites and therefore the finer tuning of neural interconnections.

Animals↗
PubMedDate not supplied

Information cascade from primary auditory cortex to the amygdala: corticocortical and corticoamygdaloid projections of temporal cortex in the rat.

Corticocortical and corticoamygdaloid connections of temporal cortext and perirhinal cortex (PRh) were examined in the rat with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). Iontophoretic injections of PHA-L into area TE1 resulted in columnar axonal terminations in surrounding and contralateral regions of temporal neocortex and in the striatum, but not in the amygdala. Within temporal neocortex, labeled fibers were present locally in adjacent regions of TE1, as well as in TE2d, TE1v, TE3v, and TE2c. Injection of cortical areas TE1v, TE3v, and TE2c, which received projections from TE1, or injections of perirhinal periallocortex, which received projections from TE1v, TE2v, and TE3v, resulted in projections to the amygdala. The pattern of corticocortical and corticoamygdaloid projections differed among the divisions of auditory cortex. TE1 exhibited extensive ipsilateral and contralateral projections to temporal cortical regions and no projections to the amygdala. In contrast, areas of temporal neocortex ventral and posterior to TE1, including TE1v, TE3v, TE2c, and PRh, had more limited ipsi- and contralateral corticocortical projections but had an increased connectivity with the subcortical forebrain, especially the lateral nucleus of the amygdala (AL). There was a topographic organization to the AL afferents. The dorsal subdivision of AL received projections from TE1v, TE3v, TE2c, and PRh, while the ventrolateral division received projections from TE3v, TE2c, and PRh. The ventromedial division received projections only from PRh, which, unlike other temporal cortical areas, also projected to the basolateral and basomedial nuclei of the amygdala. These findings define the complete sequence of connections linking primary auditory cortex with the amygdala in the rat. In addition, the findings indicate that the ventral portion of TE1, designated TE1v, has connections that distinguish it from dorsal TE1, namely, dense projections to AL and a diminished number of corticocortical projections ipsilaterally and contralaterally. Finally, the results suggest a topographic organization to the cortical terminations within the amygdala.

Amygdala↗