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At least 37 records · Page 2Linked to original sources
PubMed1976

Experimental bilateral deep temporal epilepsy. Effects of ablation of one focus and of different brain lesions.

In acute experiments in the rabbit, the amygdaloid nuclear complexes of the two sides were made epileptogenic through electrical stimulation or local injection of penicillin in gel. The effects on the epileptic pattern produced by surgical removal of one of the two epileptogenic amygdalae and the effects of sterotactic lesioning of the region of anterior commissure, head of caudate nucleus, and occipital cortex were analyzed. The occurrence of phenomena of both inhibitory and facilitatory interaction between the two epileptogenic amydalae was confirmed. In some experimental conditions, the restraining influence of an amygdaloid penicillin focus on the contralateral one was quite relevant, and its effect could persist even after surgical removal of the focus from which it originated. The mediation of the interamygdadoid epileptic interaction could not be ascribed to a single cerebral structure or anatomofunctionally homogenous group of structures. The phenomenon appears to involve several structures at different encephalic levels.

Amygdala↗
PubMed1977

Somatosensory properties of spinoreticular neurons in the cat.

(1) Spinal cord neurons projecting to the brain stem were studied in cats prepared by decerebration or anesthetized with barbiturate or nitrous oxide and halothane. Antidromic stimulation from the medial pontomedullary reticular formation (MDRF) and midbrain (MB) was used to identify the site of projection. (2) Receptive fields were mapped using adequate stimuli. A variety of noxious stimuli was employed to establish the capacity of these neurons to transmit nociceptive input. (3) Neurons were found to project bilaterally to the MPRF. Of 46 units tested for a more rostral projection, only 13 were activated from the MB electrode. (4) Neurons fall into three categories based on receptive fields: cutaneous, restricted (SR); deep, restricted (DR); and complex, extensive (CE). All 16 SR neurons were located in the dorsal horn and had low thresholds to mechanical stimulation of the skin. Seven discharged maximally to nociceptive inputs. The 34 DR neurons were widely distributed in the spinal gray and responded to pressure upon subcutaneous structures. Although 13 neurons increased their firing rate as the stimulus intensity was increased into the noxious range, nociceptive input could only be established with confidence in 4 neurons. The 38 CE neurons were located ventrally in the spinal gray and had highly convergent inputs from cutaneous and deep receptors. Ten responded maximally to noxious stimulation.

Afferent Pathways↗
PubMed1975

[Mixed and antidromal cortical responses evoked by electrical stimulation of the splenial portion of the corpus callosum].

In anesthetized cats, antidromic and orthodromic components were shown to be represented unequally in the mixed responses to the splenium stimulation recorded from various areas of the cortex. Orthodromic component makes about 50 per cent of the mixed response amplitude in the area 17, while in the area 18 and in middle part of the suprasylvian gyrus it makes about 70 per cent. In the regions beyond focus the mixed responses disappeared because of falling out of the orthodromic impulses. During antidromic recording of the responses, only deep layers got activated at weak stimuli, while both deep and superficial ones were involved at stronger stimulation.

Animals↗
PubMed1976

[An analysis of EEG rhythm changes following micropolarization of several brain structures].

With the aid of the EEG special statistical analysis, micropolarization of the temporal cortex of hypothalamus was shown to entail abrupt alterations of the theta-, alpha-, and beta-rhythms in the temporal and motor cortex, hypothalamus, and the midbrain RF. The changes of the biorhythms (their correlation, thresholds of occurring, connection of the local and distant shifts) are regarded as reflecting some fine regulation of the structures' functional condition as well as mutual influences of the cortex and the deep brain structures which tell on modulation of mnemic processes.

Animals↗
PubMed1976

[Somatosensory evoked brain potentials in discogenic compressions of the lumbosacral roots].

In 16 patients with discogenic lumbar-sacral radiculitis the author studied somato-sensory evoked potentials from the vertex area in response to electric stimulation of the peripheral nerves corresponding to the affected radicle on the side of the compression and on the intact side. It was established that in discogenic compressions of the radicles there is an expressed drop in the amplitude of early components of evoked potentials II1, H1, especially if the compression leads to disturbances of tacticle, double-range and deep sensitivity. The degree of changes in evoked potentials corresponds to the severity of the compression and may serve as one of the criteria for evaluating the effectiveness of conservative therapy and determination of indications to surgical treatment.

Brain↗
PubMed1978

Studies on the influence of monoamines on the cerebrovascular response to arterial hypoxia.

The cerebrovascular response to arterial hypoxia was studied during blockade of the vascular dopamine receptors and during alpha-adrenergic receptor stimulation and blockade in anaesthetized dogs. Dopamine receptor blockade with pimozide or haloperidol invariably decreased the degree of hypoxic vasodilatation in the brain pointing to a functional role of dopamine in this situation. Alpha-receptor blockade did not change the response, while stimulation of these receptors decreased the dilatory response even in deep arterial hypoxia.

Animals↗
PubMed1976

[An analysis of the electrical responses of the neocortex evoked by stimulation of different hypothalamic structures].

Evoked potentials and extracellular spike activity during stimulation of the posterior, lateral, anterior, and ventro-medical hypothalamus were recorded in different areas of the neocortex in unanesthetized cats. Hypothalamo--cortical evoked potentials (HC EP) of maximal amplitude are generated in gyr. sigm. ant. with 0.5--2.5 msec latency. The responses are of positive--negative configuration and often a fast spike--like defiction appears at the positive phase. EP in gyr. suprasylv. med. are initially negative and of 2--6 msec latency. Most effective is stimulation of the posterior and lateral hypothalamus, HC EP in gyr. sigm. ant. following the frequency of stimulation up to 200/sec and being characterized not only by a high "functional lability" or reproducibility but also by the ability of posttetanic potentiation. With the aid of paired stimuli, the early fast component of the EP in the sensorimotor cortex was shown to appear at an interval of approximately 2 msec. HC EP entirely recover 50--150 msec after the conditioning stimulus. The recovery cycle is biphasic and reflect, a biphasic change of the excitability of neurons in gyr. sigm. ant. and suprasylvian associative areas of the cortex. The latency of evoked discharges of some neurons of the sensorimotor cortex during stimulation of the posterior hypothalamus, is 0.8--1.5 msec, which suggests the existence of a monosynaptic pathway for the hypothalamo--cortical discharges. The maximal amount of neurons in deep layers of gyr. sigm. ant. respond during development of the early and the main positive deflections of HC EP.

Animals↗
PubMed1978

Brain energy metabolism and alterations of transmitter profiles in acute hepatic coma.

Brain energy reserve, tricarboxylic cycle intermediate and some putative neurotransmitters were measured in a devascularisation model with portacaval shunt and hepatic artery ligation done in two interventions. Conditions were standardized in that physiologic parameters, i.e. body temperature, systemic arterial pressure, PO2, PCO2 and pH, were kept constant and brain tissue was obtained with the "freeze-blowing" technique designed for deep freezing brain substance in less than one second. 1. Measured values indicative of the brain energy reserve (glucose, glycogen, ATP and phosphocreatin) were not found to differ from those of sham-operated animals. 2. Of the stimulating neurotransmitters, norepinephrine, dopamine, glutamic acid and aspartic acids were reduced with the exception of acetylcholine among the inhibitory neurotransmitters GABA and cAMP were unchanged, while all others including serotonin, octopamine, and phenylethanolamine were increased. 3. The results of these experiments suggest that an inbalance of amino acids with resultant changes in neurotransmitter profiles rather than an energy deficit constitutes the factor underlying hepatic coma.

Adenosine Diphosphate↗
PubMedDate not supplied

Afferent projections to the self-stimulation regions of the dorsal pons, including the locus coeruleus, in the rat as demonstrated by the horseradish peroxidase technique.

Afferent projections to the dorsal pons of the rat have been studied using the horseradish peroxidase (HRP) technique. HRP injections were made in each of the following regions: the vicinity of the locus coeruleus (LC); the periventricular gray, medial to the LC; the medial parabrachial region, lateral to the LC; the ventral cerebellum, dorsal to the LC; and the pontine reticular formation, ventral to the LC. Because intracranial self-stimulation (ICSS) has been obtained in these regions, the afferents have been discussed in terms of their possible contributions to the behavior. Previous ICSS studies of the dorsal pons have focussed on the LC as playing a central role. Presently identified inputs to the LC include: the dorsal raphe nucleus: the ventrolateral periaqueductal gray: the pontine reticular formation: the areas that contain the pontine and medullary noradrenergic and adrenergic cell groups: the lateral hypothalamic area: the contralateral LC: the deep cerebellar nuclei: the ventrolateral and parafascicular thalamic nuclei: and the parabrachial regions of the pons and midbrain.

Afferent Pathways↗
PubMed1992

Investigation of stroke in sickle cell disease by 1H nuclear magnetic resonance spectroscopy.

Localized proton nuclear magnetic resonance spectroscopy (MRS), obtained with stimulated echo and spin echo sequences, MR imaging (MRI) and MR angiography (MRA) were used to study the brain in 13 children and adolescents with sickle cell disease. Regions of interest (ROI) studied by MRS included regions appearing normal on MRI as well as regions showing complications of sickle cell disease, including focal deep white matter areas of high signal intensity (deep white matter ischemia, DWMI) seen on long TR images, focal atrophic brain areas, and infarcts. The findings in these studies are summarized as follows: Normal-appearing regions on MRI have normal MRS. In ROI including small areas of DWMI, lactate elevation was not detected, but the levels of N-acetyl-aspartate (NAA) appeared slightly elevated. In areas of DWMI 1-2 cm in size, reduced blood flow could be seen on MRA and lactate elevation could be detected with MRS. When blood flow to a DWMI region was normal, NAA was reduced and there was little lactate elevation, as cell death had already occurred. ROI consisting of atrophic tissue had reduced NAA levels but total creatine levels were not changed. Sometimes lipids, presumably from broken cell membrane, could be detected. In regions of past massive stroke, all metabolites were absent except for small amounts of lactate or lipids.

Adolescent↗
PubMed1979

[Cerebral Function Monitor (CFM) and electroencephalography (EEG). Experimental study].

This work is an attempt to connect the electro-encephalogram (EEG) and monitor of cerebral function (MCF) recordings during the experimental stimulation of the rabbit brain whether this is in the from of direct central stimulation, by stereotaxic location, or in the form of indirect stimulation via a peripheral nerve. These stimulations, performed under alfadione anaesthesia or under the neuroleptanalgesic sedative effect of chlorprothixine, are compared for every animal with the results of the control stimulations. The cardiovascular responses are recorded simultaneously. It has been found that, in simple narcosis induced by alfadione, there is much variation in the EEG recording and even more so in the MCF recording according to the quantity used and the block of responses to stimuli does not appear until there is deep anaesthesia. However, when chlorprothixine is used, the MCF trace is found to be very closely related to the trace of mild anaesthesia with accompanying block to all of the nociceptive stimulations. It would seem, therefore, if we accept the concept of levels of cerebral activity, that the use of the MCF could well open the way to a better understanding of the pure narcotic phenomena and of the neurovegetative response block to aggression.

Alfaxalone Alfadolone Mixture↗
PubMed1979

Jakob-Creutzfeldt disease: analysis of EEG and evoked potentials under basal conditions and neuroactive drugs.

EEG and evoked potential (EP) recordings of a female (aged 70) affected with Jakob-Creutzfeldt disease (JCD) are reported. A comparison of neurophysiological tests under basal conditions and pharmacological stimulation with methylphenidate, diazepam and piracetam was performed. Diazepam and methylphenidate produced a flattening of triphasic complexes and changes in background activity; piracetam did not seem to influence the abnormal brain bioelectrical environment. The authors conclude that EEG and EP abnormalities in JCD can be ascribed to two separate and interacting sources: (1) exaggerated massive excitatory input coming from a deep thalamic pace-maker throughout the diffuse projecting system, and (2) lack of inhibitory intracortical mechanisms.

Aged↗
PubMed1978

Functional and anatomical consequences of neonatal visual cortical damage in superior colliculus of the golden hamster.

1. In normal hamsters the visual cortex sends a retinotopically organized projection to the ipsilateral superior colliculus. 2. Acute or chronic unilateral ablations of visual cortex in adult animals decrease the incidence of directionally selective cells encountered in the superficial laminae of the ipsilateral colliculus, but not in the deeper layers (those ventral to the stratum opticum). 3. Unilateral ablations of visual cortex in infant hamsters induce an aberrant crossed projection to the contralateral superior colliculus, confirming the finding of Mustari and Lund (58) in the rat. Horseradish peroxidase (HRP) experiments demonstrated that the cells whose axons comprise the normal as well as the anomalous projection are pyramidal neurons in layer V of cortex. 4. In adult hamsters that underwent early brain damage, about 13% of the cells in the colliculus could be activated by stimulation of the contralateral visual cortex. Only 1 unit (of the 159 cells tested) could be driven by similar stimulation in normal adult hamsters. This indicates that the anomalous crossed projection forms functional synapses in the contralateral tectum. 5. No cells (of the 113 tested) could be activated from the contralateral cortex in hamsters that sustained chronic ablations of visual cortex in adulthood; thus indicating that there is some limited time period during development when unilateral ablations of visual cortex induce an anomalous corticotectal pathway. 6. The visual response properties of superior collicular neurons in the neonatally brain-damaged animals were compared to those of normal hamsters, as well as to those with acute or chronic ablations of visual cortex sustained in adulthood. 7. There was no indication that the anomalous projection contributes to the organization of normal visual response properties in the superior colliculus of the neonatally brain-damaged animals. In fact, the incidence of directionally selective cells in these hamsters was found to be significantly lower than that of normals in both the superficial and deep laminae of the colliculus. 8. We conclude that while unilateral damage of visual cortex in the hamster induces an anomalous corticotectal projection that makes functional synapses, this aberrant input does not compensate for missing, normal corticotectal pathway in the organization of superior collicular response properties.

Animals↗
PubMedDate not supplied

[Post-tetanic strengthening of evoked electrical responses of the sensomotor cortex].

A study has been made of the posttetanic potentiation of evoked potentials (PTP EP) in the sensorimotor cortex, appearing in response to VPL stimulation. A distinct PTP EP of the cortical surface has been found as well as considerable differences in its intensity recorded at different portions of deep cortical layers (700 to 1600 mu). Suggestions were made regarding the origin of the phenomena observed.

Animals↗
PubMed1979

[Configuration of the electrical field of an evoked potential in in the superiod colliculus of the rabbit brain upon punctiform afferent stimulation].

Evoked potentials were studied in the rabbit superior colliculus to punctiform light stimulation of the receptive field. The evoked potentials were of negative polarity and did not show potential reversion. The depths of recordings were from 0.1 to 1 mM. The 4-6 degrees shift of the punctiform stimulus from the optimal position led to the disappearance of the evoked potential. If large (more than 5-6 degrees) or diffuse stimuli were used the evoked potentials reversed from surface-negative to deep-positive at a depth of 0.3-0.4 mM. It is suggested that the evoked potential to punctiform stimuli indicate more precisely the location of afferent synapses.

Animals↗
PubMed1979

Short-latency peripheral inputs to thalamic neurones projecting to the motor cortex in the monkey.

One hundred seventy-five neurones in the n.ventroposterior lateralis (VPL) and n.ventralis lateralis (VL) in the thalamus of anaesthetised monkeys have been tested antidromically for projection to the cortex and for somatosensory input from the contralateral arm. Using bipolar stimulation of the cortical surface, 113 thalamic neurones were successfully identified as antidromically driven from the hand area of the postcentral gyrus (48 neurones) or from the hand area of the precentral gyrus (65 neurones). All but one of these 113 neurones could only be antidromically discharged from the postcentral cortex or from the precentral cortex, and not from both. Most had antidromic latencies between 0.5 and 1.5 ms. Twenty-five/sixty-five precentrally projecting neurones and 45/48 postcentrally projecting neurones were activated by stimulation of the contralateral median or radial nerves. Both groups responded at short latency (4--8 ms) and many were activated by low-threshold shocks (0.8--1.3 T) and had restricted receptive fields on the hand. Precentrally projecting neurones responded most powerfully to joint movement or deep pressure, and some of these neurones were also responsive to cutaneous stimuli. Precentrally projecting neurones with peripheral inputs were all found in the oral subdivision of the VPL (the VPLO). The properties of these neurones suggest that they may be partly responsible for rapid somatosensory input to the motor cortex.

Afferent Pathways↗