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At least 253 records · Page 14Linked to original sources

PubMed1999

Organization of somatosensory areas I and II in marsupial cerebral cortex: parallel processing in the possum sensory cortex.

Organization of somatosensory areas I and II in marsupial cerebral cortex: parallel processing in the possum sensory cortex. Controversy exists over the organization of mammalian thalamocortical somatosensory networks. An issue of particular contention is whether the primary and secondary somatosensory areas of cortex (SI and SII) are organized in a parallel or serial scheme for processing tactile information. The current experiments were conducted in the anesthetized brush-tail possum (Trichosurus vulpecula) to determine which organizational scheme operates in marsupials, which have taken a quite different evolutionary path from the placental species studied in this respect. The effect of rapid reversible inactivation of SI, achieved by localized cortical cooling, was examined on both evoked potential and single neuron responses in SII. SI inactivation was without effect on the amplitude, latency, and time course of SII-evoked potentials, indicating that the transient inputs responsible for the SII-evoked potential reach SII directly from the thalamus rather than traversing an indirect serial route via SI. Tactile responsiveness was examined quantitatively before, during, and after SI inactivation in 16 SII neurons. Fourteen were unchanged in their responsiveness, and two showed some reduction, an effect probably attributable to the loss of a facilitatory influence exerted by SI on a small proportion of SII neurons. The temporal precision and pattern of SII responses to dynamic forms of mechanical stimuli were unaffected, and temporal dispersion in the SII response bursts was unchanged in association with SI inactivation. In conclusion, the results establish that, within this marsupial species, tactile inputs can reach SII directly from the thalamus and are not dependent on a serially organized path through SI. A predominantly parallel organizational scheme for SI and SII operates in this representative of the marsupial order, as it does in a range of placental mammals including the cat and rabbit, the tree shrew and prosimian galago, and at least one primate representative, the marmoset monkey.

Animals↗

PubMed2002

Motor cortex stimulation in the treatment of deafferentation pain. I. Localization of the motor cortex.

MRI and electrophysiological techniques to localize the primary motor cortex (MC) were performed on patients considered for MC stimulation for the treatment of deafferentation pain. The representation and trajectory of the rolandic fissure (RF) were accurately localized by external cranial landmarks and radiopaque fiducials superimposed on oblique MRI sections. In addition, the scalp distribution of the corticocortical responses elicited by acute epidural stimulation [motor cortex (MC) in frontal and sensory cortex (SC) in parietal scalp regions], and analgesic responses at the topographical representation of the painful periphery elicited by subacute epidural stimulation were found to be simple and reliable procedures to localize MC, SC and RF.

Causalgia↗

PubMed1998

Interaction between midazolam-induced anterograde amnesia and memory enhancement by treatments given hours later in hippocampus, entorrhinal cortex or posterior parietal cortex.

Rats were bilaterally implanted with indwelling cannulae in the CA1 region of the dorsal hippocampus, the entorrhinal cortex or the posterior parietal cortex. After recovery from surgery, they were trained in a one-trial step-down inhibitory avoidance task using a 0.3 mA footshock. The animals received i.p. 15 min before training either saline (1 ml/kg) or midazolam (1 mg/kg). Three hours after training they received, through the cannulae, infusions of saline, norepinephrine (0.3 microg/side), SKF38393 (7.5 microg/side), or 8-Br-cAMP (1.25 microg/side) into the brain regions mentioned. Animals were tested for retention 24 h after the training session. Midazolam produced anterograde amnesia, and the post-training treatments (with the exception of SKF38393 given into the entorrhinal cortex) caused retrograde memory facilitation. The amnestic effect of midazolam and the facilitatory effect of the treatments given into the brain cancelled each other out. Therefore, the mechanisms triggered by midazolam can interact with others in areas involved in memory processing several hours after their onset.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2001

Focal ischemia in the cerebral cortex has an effect on the neurohypophysis. II. Angiogenesis in the neurohypophysis is a consequence of the focal ischemia in the cerebral cortex.

OBJECTIVES: Focal ischemia in the cerebral cortex has an effect on neurohypophysis. The morphological changes of microvessels of neurohypophysis were evaluated in a model of the cerebral infarction initiated by a photochemical reaction in the cerebral cortex. After photochemically induced platelet aggregation, we observed the morphological features of angiogenesis. METHOD: The model of photochemically-induced cerebral ischemia was used. Seven days after intravenous injection of rose bengal and irradiation from a halogen lamp source through an intact cranium, the sampled material from neurohypophysis is processed for transmission electron microscopy using standard procedures. RESULTS: We observed morphological features of the new vessel formation: the alterations in the endothelium and extracellular matrix during separation of the endothelial cell from each other in a "mother" vessel, the migration of the endothelial cells in the extracellular matrix, the communication of the lumen of the new and the "mother" vessels. CONCLUSION: We observed development of the angiogenic phenotype in the neurohypophysis after focal ischemia in the cerebral cortex. The endothelium, basement membrane and extracellular matrix undergo morphological alterations which lead to new blood vessel formation.

Animals↗

PubMed2002

Interaction of ventral and orbital prefrontal cortex with inferotemporal cortex in conditional visuomotor learning.

Five rhesus monkeys (Macaca mulatta) were trained to learn novel conditional visuomotor associations, to perform this task with familiar stimuli, and to perform a visual matching-to-sample task with the same familiar stimuli. Removal of the orbital and ventral prefrontal cortex (PFv+o) in 1 hemisphere and inferotemporal cortex (IT) in the other, thus completing a surgical disconnection of these 2 regions, yielded an impairment on all 3 tasks. Addition of a premotor cortex lesion to the hemisphere containing the PFv+o lesion did not worsen the impairments. The results indicate that PFv+o interacts with IT in both the learning and retention of conditional visuomotor associations. In addition to those associations, which might be considered lower order rules for choosing a response, frontotemporal interaction also appears to be important for higher order rules, such as those involved in the matching task.

Animals↗

PubMed1990

[The characteristics of the synaptic reorganization in the sensorimotor cortex of cats after the destruction of the symmetrical portion of the cortex in the opposite hemisphere].

Intracellular recording technique has been used to study reactions of corticospinal neurons (CSN) to stimulation of the ipsilateral ventrolateral nucleus (VLN) of the thalamus in acute experiments on adult intact cats and on cats after lesion on the contralateral sensorimotor cortex (exposition from 6 months to 1.5 years). Acceleration of the monosynaptic EPSPs rise phase in slow CSN was revealed in operated animals, which presumed the reorganization of the synaptic contacts in the SD membrane of flow CSN. Detailed analysis of features and branching of CSN axon, collaterals passing to VLN of the thalamus and participating in formation of the ipsilateral pyramidal tract was made by the method of collision test. The significance of the plastic synaptic reconstruction in the ipsilateral thalamo-cortex reverberating system during the outflow formation under conditions of the partial cortex interhemisphere deafferentation is discussed.

Animals↗

PubMed1986

A study on the microvasculature of the cerebral cortex. Fundamental architecture and its senile change in the frontal cortex.

The arterial architecture of the cerebral cortex and its changes along with aging were studied by microangiography, vascular staining, and scanning electron microscopy. The arteries distributed in the cerebral cortex and medulla were classified into cortical, subcortical, and medullary arteries. The cortical arteries were further classified into superficial, middle, and deep cortical branches according to the site of their termination. There were many fountain-like rami in the middle and deep cortical branches. These fountain-like rami were composed of several to many fine arteries, ramified from a small artery by repeated bifurcation within a short segment of its course. This structural pattern is probably responsible for the ease with which pronounced ischemic state may develop in their territories nourished by these branches, and they may play a significant role in the development of pseudolaminar necrosis of the cerebral cortex. Intertwining of small branches forming rope-like structures was observed with increasing frequency with age, suggesting that this phenomenon correlates with aging or is associated with brain atrophy. The intertwining was always clockwise when looking from the proximal side of the arteries towards their distal end. While the precise mechanism of the development of the intertwining remains unclear, torsion of the trunk of the blood vessels is thought to be the cause of the intertwining of the peripheral branches.

Adolescent↗

PubMedDate not supplied

[The involvement of the cerebral cortex, hypothalamus, pituitary and adrenal cortex in the development of periodontosis].

The authors emphasized in parodontosis patients functional alterations of hypothalamic centres with phagocytosis-stimulatory, vasomotor and neurotrophic functions and disturbances of the functional relationship between the hypothalamus (H), the ascendent reticular formation (RF) and the cerebral cortex (CC). Stimulatory therapy of this areas, especially by direct stimulation of the H improves the hypothalamic functions, the relationship between H and the RF and all the clinical status of parodontosis patients. In rabbits with experimental parodontosis have been found functional and histological alterations in cerebral cortex, and especially in hypothalamus, together with lesions in the hypothalamo-posthypophyso-neurosecretoric system, in the anterior pituitary (P) cells (for ACTH, TSH and FSH) as well as in zona fasciculares of the adrenal cortex (AC). This data, together with findings of other authors, prove that parodontosis is a diencephalopathy involving a whole system: CC-H-P-AC.

Aggressive Periodontitis↗

PubMed1985

[Modulating influence of the 2d somatosensory cortex of the cerebral cortex on the effects of electroacupuncture on the trigeminal nuclei].

The effect of reversible functional inactivation of the second somatosensory cortex of the cerebral hemispheres on changes in the transmission of the afferent signals in the trigeminal nuclei after electroacupuncture was studied in acute experiments on adult cats anesthetized with hexenal (59 mg/kg i. p.). After functional inactivation of the second somatosensory cortex electroacupuncture failed to facilitate the evoked potentials in the oral trigeminal nucleus by stimulation of the tooth pulp and the lip of the mouth. In the caudal nucleus, the inhibitory effect of electroacupuncture on noxious stimulation decreased. The involvement of this brain cortex in the mechanisms of action of electroacupuncture on functionally different nuclei is discussed.

Acupuncture Therapy↗

PubMed1983

[Functional relations of the adrenal cortex, thyroid and pineal body. II. Adrenal cortex reaction following epiphysectomy and administration of melatonin].

Histologic-cytological and morphometrical changes were investigated in the adrenal cortex of male Wistar-rats following pinealectomy and application of melatonin in eu-, hypo-, and hyperthyroid situations. A rat experiment (at an average of 45 d) to find a possible functional connection between the pineal gland and the adrenal cortex was carried out. In the literature, there are only a few of informations about the role of the pineal in regulating ACTH secretion. The results are very contrarily. We found that pinealectomy is connected with a progressive transformation and melatonin with a little regressive transformation in the adrenal cortex. But, it is not evident, that the glomerular zone is activated after both pinealectomy and application of melatonin. In our opinion, the glomerular zone and the secretion of aldosterone increased after as well pinealectomy as melatonin. Application of melatonin diminishes the function of the pineal gland (see group 4-pinealectomy plus melatonin-where was found a progressive transformation). Under these experimental conditions, one can speak of a "pharmacological pinealectomy" after application of melatonin alone. However, the effect of melatonin on the fascicular zone and the glomerular zone is different. The effects of pinealectomy or application of melatonin in combination with methylthiouracil or thyroxin are relatively unimportant.

Adrenal Cortex↗

PubMed1994

Projections from the primary auditory cortex onto the dorsal cortex of the inferior colliculus in albino rats.

The topography of connections from the primary auditory cortex (Te1) onto the dorsal cortex (DC) of the inferior colliculus (IC) was studied using the anterograde neural tracers Phaseolus vulgaris (PHA-L) and Biotinylated dextran amine (BDA). Injections in different restricted portions of the ventral Te1 showed labelled axonal sheets in the ipsilateral DC with extensions in the central nucleus and the external cortex. Also contralateral labelled axons were found with a patchy appearance. The pattern of labelled axonal laminae is arranged in an orderly fashion, so that a correlation exists between the injection field (antero-to caudoventral injections) and the pattern of labelled axonal sheets (from a ventromedial to a dorsolateral arrangement) in the IC. However, variations from this pattern were observed. Also only the injections made in rostral and middle parts of Te1 V are orderly arranged in the territory of the DC, while the Te1 V caudoventral projection partially overlaps those from antero and mid-central regions. A topographical arrangement in the fibre projection from the medial and dorsal zones of Te1 (Te1 D) exists in the neuropil of the IC. The bands from Te1 D overlapped with the bands from Te1 V but in different order. This indicates that the projection of the mid-dorsal zone of Te1 is not topographically arranged in the DC like Te1 V. Based on the results we have obtained, there is strong evidence that the projection from Te1 V to the DC is topographically organized in a rostrocaudal sequence which gives definite terminal fields. However, each of these fields (medial, central and external) receives a principal bulk of primary auditory cortical fibres and a supplementary one. This implies that territories of the DC which contain neurons responsive to low frequencies receive a projection from Te1 fields with neurons which are responsive to high or to low frequencies.

Acoustic Stimulation↗

PubMedDate not supplied

[The plastic reorganization of the neuronal receptive fields of the auditory cortex and medial geniculate body evoked by microstimulation of the auditory cortex].

The effects of intracortical microstimulation (ICMS) on receptive fields (RFs) of simultaneously recorded auditory cortex (A1) and medial geniculate body (MGB) neurons were examined in rats under ketamine. Three types of neurons were distinguished according to the configuration of their RFs: mono-, be-, and polymodal. It was shown that RFs of adjacent neurons may be different and Rfs of distant (up to 1 mm in rostro-caudal direction) neurons may be similar. ICMS was able to produce changes in RF structure of A1 neurons at and near the stimulation side and also in homotopically related regions of MGB. RFs of homotopically related A1 and MGB neurons mostly changed in a similar way after ICMS. We suggest that the mechanism underlying the observed RF changes of A1 and MGB neurons in related to ICMS-induced long-term changes (LTP and LTD) in synaptic efficacy of the cortex-thalamus-cortex loop.

Acoustic Stimulation↗

PubMed1993

[Effect of electrical stimulation of second somatosensory cortex on the response of primary somatosensory cortex to C-fiber inputs].

When the projecting point of saphenous nerve in second somatosensory cortex (S II) of cat was stimulated, the evoked potentials elicited by C-fiber inputs of saphenous nerve recorded in the primary somatosensory cortex (C-CEP) might be either inhibited or facilited according to whether the superficial and/or the deeper layer of the cortex was stimulated. The inhibition was expressed as a decrease of amplitude and prolongation of latency of C-CEP; while the facilitation, as an increase of amplitude and duration of C-CEP. When the superfaicial layer of S II was stimulated by weaker current, both inhibitory and facilitatory effects could be observed, but only inhibitory effect was observed, when the deep layer was stimulated. With the same intensity of stimulation, inhibitory effect was more pronounced when the deep layer rather than the superficial layer was stimulated. It is suggested that S II may play a role in the modulation of C-CEP of S I.

Animals↗

PubMed1982

[Neuronal responses of the intact cortex and isolated strips of the sensorimotor cortex to systemic administration of thyroxine].

The pattern of neuronal responses to alterations in hormonal homeostasis was specified. A study was made of neuronal responses of intact and neuronally isolated strips of the sensorimotor cortex (ISC) to intravenous injection of thyroxine. The neuronal response of the ISC was found to differ substantially from the response of intact cortical neurons. Less percentage of the responding neurons was registered in the ISC. The responses were considerably shortened, while the neurons discharged at a lower frequency. The differences indicate that, as compared to subcortical structures, the cortical neurons are less susceptible to blood hormones. It is emphasized that subcortical structures, particularly the hypothalamus are of major importance for transmission of hormonal influences to the brain cortex.

Action Potentials↗

PubMed1981

Tridimensional study of the deep cortex of the rat lymph node. III. Morphology of the deep cortex units.

Recently we reported that the deep cortex of the rat lymph node is made up of semi-rounded "units," some of which are partially fused into "complexes." We further found that each unit is centered on the opening(s) of an afferent lymphatic vessel, the topographical organization of the deep cortex of a node correlating with the distribution pattern of the opening(s) of its afferent lymphatic(s). The present study aims to clarify the morphology of the deep cortex unit, particularly with regard to its reticular framework, its lymphatic sinuses, as well as its network of postcapillary venules. For that purpose, we analyzed rat nodes from various locations by way of tridimensional reconstruction. The observations revealed that each unit is formed of a "center" and a "periphery," distinguishable from one another on the basis of their morphological features. The center is nearly devoid of reticular fibers, whereas the periphery exhibits a dense framework of fibers. Moreover, the periphery is the site of concentration of most postcapillary venules of a unit and contains lymphatic sinuses which, peculiarly, are often loaded with small lymphocytes. While both regions are populated mainly by small lymphocytes, the periphery usually contains a lower concentration of these cells than the center. The overall findings support the view that the center is a site of cellular retention and proliferation, whereas the periphery is a site of rapid lymphocyte migration in and out of the unit.

Animals↗

PubMed1984

Tridimensional study of the deep cortex of the rat lymph node: VIII. The deep cortex units of the athymic nude rat.

The deep cortex of the lymph node of various species actually consists of hemispherical structures, termed deep cortex "units." Each unit is centered under an opening of an afferent lymphatic and comprises a center and a periphery. In a recent work on the nude mouse, we found that the congenital athymic state inhibits the development of the lymphocyte population in the center of the units as well as in a related area of peripheral cortex, and that it also modifies other nodal components. In the present work, we wanted to compare the effects of the athymic state on the rat nodes. Therefore, nodes from various anatomical locations in 8-week-old nude rats were submitted to a tridimensional analysis. The overall effects of the congenital athymic state were found to be comparable in rats and mice. However, marked differences were noticed in the modifications of the node histology, in both species of nude animals. Their significance is discussed together with new findings.

Animals↗

PubMed1986

The medial frontal cortex and gastric motility: microstimulation results and their possible significance for the overall pattern of organization of rat frontal and parietal cortex.

Bilateral intracortical microstimulation (60-90 strains of 0.5 ms pulses at 10 Hz, currents below 50 microA) of medial frontal infralimbic and prelimbic cortical areas in ketamine-anesthetized rats produces clear and consistent decreases in ongoing gastric motility. The majority of responses consists of reductions in gastric tone, reductions in the amplitude of gastric contractions, or combined reductions in tone and amplitude. Bilateral section of the vagus nerves eliminates most of the responses, suggesting that the responses are mediated by this nerve. The effective cortical stimulation zone (the 'visceral motor' cortex) largely overlaps the source of the recently described direct projection from medial frontal cortex to the nucleus of the solitary tract; this pathway may be involved in producing the effect. Connections of this cortex with the limbic system suggest it may be involved in producing physiological responses to stress. The topographical, medial to lateral sequence of cortical functional areas revealed by these and other experiments (visceral motor, frontal eye fields, somatic motor, somatic sensory, visceral sensory) is discussed, as well as the possible implications of this pattern to the question of cortical evolutionary development.

Animals↗

PubMed1986

Adult and embryonic frontal cortex transplants after frontal cortex ablation enhance recovery on a reinforced alternation task.

Damage to the medial frontal cortex in rats results in a learning deficit on a reinforced alternation task. The rate of recovery from this deficit was accelerated by transplantation of either adult or embryonic frontal cortex, provided that a delay was introduced between injury and transplantation. The rates of recovery for both delayed embryonic and adult transplants did not differ from the undamaged group. In contrast, transplants of embryonic frontal cortex immediately after ablation did not accelerate the rate of recovery. The accelerated rate of behavioral recovery on the reinforced alternation task appeared to correlate with transplant survival.

Acetylcholinesterase↗