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Results for “Sensorimotor Cortex”

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PubMed2003

Synaptic mitochondrial changes in the motor cortex following unilateral cortical lesions and motor skills training in adult male rats.

Unilateral lesions of the forelimb sensorimotor cortex and motor skills training interact to enhance synaptic plasticity in layer V of the motor cortex contralateral to the lesion in male rats. In this study, we assessed the metabolic correlates of these synaptic changes by quantifying the number and size of mitochondria in synaptic axonal terminals with perforated or non-perforated post-synaptic densities (PSDs) and single or multiple post-synaptic contacts. The number of synaptic mitochondria per neuron was significantly greater in rats with lesions. Neither manipulation affected mitochondrial size or number of mitochondria per synapse. Independent of experimental condition, terminals with perforated PSDs had more mitochondria than those with non-perforated PSDs and, among those with non-perforated PSDs, terminals with multiple synaptic contacts had more mitochondria than those forming single synapses.

Adaptation, Physiological↗
PubMed1978

Chronic focal epileptiform discharges induced by injection of iron into rat and cat cortex.

A single injection of 5 or 10 microliters of ferrous or ferric chloride into rat or cat sensorimotor cortex resulted in chronic recurrent focal paroxysmal electroencephalographic discharges as well as behavioral convulsions and electrical seizures. Recurrent focal epileptiform discharge caused by cortical injection of iron salts suggests that the development of human posttraumatic epilepsy may depend, in part, on the neurochemical alterations induced by the principal metallic ions found in whole blood.

Animals↗
PubMedDate not supplied

[Estimation of the interaction strength in the rabbit sensomotor cortex neurons before and after formation of the defense focus].

The strength of interaction between neurons in the sensorimotor cortex of rabbits was compared before and after the formation of a hidden excitatory focus (dominant) in this cortical area. In control experiments the interactions between the neurons was significantly stronger in cases when the influence of the neurons with higher spike amplitude on the neurons generating lower-amplitude pulses was assessed. This difference disappeared in the dominant focus.

Animals↗
PubMedDate not supplied

[Aspects of the reactions of mitochondrial populations in neurons of the sensory motor cortex during prolonged influence of low-frequency vibration of rats].

Hypertrophied mitochondria (Mt) were found in the sensorimotor cortex neurons under prolong low-frequency vibration in the experiment with 66 white rat males. Structural changes of Mt were similar to those shown under other types of stress accompanied by energy supply deficit. The results indicated that the reaction of the Mt population on low-frequency vibration has stages and lead to formation of uniformity in structural and functional properties of Mt regardless of the neurons type.

Animals↗
PubMed2000

Specific versus nonspecific brain activity in a parametric N-back task.

In this study functional magnetic resonance imaging (fMRI) was used to examine cerebral activity patterns in relation to increasing mental load of a working memory task. Aim of the experiment was to distinguish nonspecific task-related processes from specific workload processes analytically. Twelve healthy volunteers engaged in a spatial n-back task with four levels. FMRI data were acquired with the 3D-PRESTO pulse sequence. Analysis entailed a two-step multiple regression algorithm, which was specifically designed to measure and separate load-sensitive and load-insensitive activity simultaneously, while preserving the original high spatial resolution of the fMRI signal. Load-sensitive and load-insensitive activity was found in both dorsolateral-prefrontal and parietal cortex, predominantly bilaterally, and in the anterior cingulate. As expected, the left primary sensorimotor cortex showed predominantly load-insensitive activity. Load-sensitive activity reflects specific working memory functions, such as temporary retention and manipulation of information, while load-insensitive activity reflects supportive functions, such as visual orientation, perception, encoding, and response selection and execution. Good performance was correlated with a large area of load-sensitive activity in anterior cingulate, and with a small area of load-insensitive activity in the right parietal cortex. The findings indicate that nonspecific and specific working memory processes colocalize and are represented in multiple frontal and parietal regions. Implication of this analytical strategy for application in research on psychiatric disorders is discussed.

Adult↗
PubMed2005

Motor cortex excitability after thalamic infarction.

Transcranial magnetic stimulation was used to map hand muscle representations in the motor cortex of a patient in whom infarction of the sensory thalamus deprived the sensorimotor cortex of sensory input. The threshold for activation of the motor cortex on the affected side was higher and the cortical representational maps of individual muscles were less well defined than those on the normal side. It is concluded that electrophysiological changes in cortical organisation can be demonstrated following withdrawal of, or imbalance in sensory afferent activity to the cerebral cortex in humans.

Adult↗
PubMed1985

Supraspinal convulsions induced by inverse benzodiazepine agonists in rabbits.

The electroencephalographic (EEG) effects of inverse benzodiazepine (BDZ) agonists have been studied in rabbits after i.v. administration. A dose-dependent progression of three different stages of EEG changes have been observed with inverse BDZ agonists. At first, trains of slow waves in the occipital cortex occur, followed by trains of spike-and-wave complexes in the sensorimotor cortex. These two stages are superimposed on a desynchronized cortical activity, accompanied by an enhancement of the hippocampal theta rhythm. These EEG changes parallel a state of alertness. The third stage is characterized by generalized grand-mal seizures made up of high voltage spikes in the cortical and subcortical brain areas accompanied by generalized tonico-clonic convulsions. No modification of electrical activity is observed at the level of the spinal cord. Methyl-beta-carboline-3-carboxylate (beta-CCM) (at doses higher than 0.2 mg/kg) and 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) (at doses higher than 0.4 mg/kg) elicit all three stages, whereas ethyl-beta-carboline-3-carboxylate (beta-CCE) (0.2-2 mg/kg) and N-methyl-beta-carboline-3-carboxamide (2-20 mg/kg) only elicit the first two, and finally CGS 8216 only the first. The extent of the EEG progression by inverse BDZ agonists may therefore be used as an index of the efficacy of each compound. The BDZ antagonists Ro 15-1788 and Ro 15-3505 (0.3 mg/kg or higher), which do not change the EEG pattern, block the effects of the convulsant and subconvulsant doses of the inverse BDZ agonists, giving rise to a desynchronized EEG pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Deviation of somatosensory evoked potential and lateral dominance of spike activity in iron-induced epileptic cortex of the rat.

A chronic epileptic focus was induced by a microinjection of ferric chloride solution into the sensorimotor cortex of rats. Two types of somatosensory evoked potentials (SEPs) were recorded from the cortex near the injection site. In animals showing an initial positive-negative biphasic SEP, spikes appeared in electrocorticograms (ECoGs) more frequently on the side ipsilateral to the injection site than on the contralateral side, whereas in animals showing an initial negative monophasic SEP, spikes appeared more frequently on the contralateral side.

Animals↗
PubMedDate not supplied

[Associative properties of a micropopulation of sensomotor cortex neurons].

A new cellular analog of temporary connection has been elaborated on a micropool of neurones in the sensorimotor cortex. Transmitters -- glutamate and acetylcholine, microionophoretically applied near studied neurones, served as paired signals. In case of initial reactivity to paired stimuli, a stronger excitatory effect of the US analog in comparison to that of the CS analog, all studied neurones of the micropopulation developed, within the area of the transmitters' action (less than 100 mc), specific associative rearrangements: enhancement in reactivity to the signal stimulus and reproduction of the reaction to US in response to CS. In control experiments with pseudoconditioning and reverse order of presentation of the same paired stimuli, no rearrangement was observed.

Acetylcholine↗
PubMed1977

[Correlation spectral analysis of the spontaneous impulse activity of cerebral cortex neurons].

Spontaneous unit activity in alert unrestrained rabbits was recorded simultaneously with two microelectrodes from the visual and sensorimotor cortex. The correlation analysis revealed that activity of majority of the neurons had no regular rhythm. But spectral analysis of the average correlograms showed existence of oscillations in the delta- and theta-ranges. The synergic type of interaction between cortical neurons was prevalent. Analysis of structure of the distant interaction showed the reduced probability of synergic spikes with periods 150-200 msec and less and the increased one with periods within 200-500 msec.

Animals↗
PubMed1987

Morphological features of layer V pyramidal neurons in the cat parietal cortex: an intracellular HRP study.

Layer V pyramidal neurons in the cat parietal cortex (areas 5 and 7) were investigated with intracellular HRP staining. Antidromic responses were recorded intracellularly as well as extracellularly with pontine stimulation under Nembutal anesthesia. The relationship between the latency of antidromic responses and the morphology of HRP-stained neurons was analyzed. A total of 65 neurons were stained with HRP, and sixteen of these neurons were activated antidromically with pontine stimulation. Two distinct groups of layer V pyramidal neurons were detected morphologically by intracellular HRP staining; i.e., one (F type) consisted of neurons with relatively large somata (58.4 +/- 8.1 micron X 24.5 +/- 5.1 micron, N = 11) and aspiny or sparsely spinous apical dendrites, and the other (S type) consisted of neurons with smaller somata (44.6 +/- 7.6 micron X 19.3 +/- 3.9 micron, N = 22) and richly spinous apical dendrites. These two groups showed different electrophysiological properties; i.e., the former responded antidromically to pontine stimulation at a latency shorter than 1.5 ms (namely, with a conduction velocity faster than 18 m/second) and the latter responded at a latency longer than 1.5 ms. The two neuronal types in the parietal cortex corresponded respectively to fast and slow pyramidal tract neurons (PTNs) investigated in the sensorimotor cortex. Although their morphological features were almost similar to those of PTNs, the branching pattern of apical dendrites of the F-type pyramidal neuron seemed to be different from that of fast PTNs. In the parietal cortex, apical dendrites of F-type neurons showed rather frequent branching in layer I. This was similar to the pattern of branching in slow PTNs. Such a characteristic branching pattern suggested that, in the cat parietal cortex, layer V pyramidal neurons of both types are adapted to receive cerebellar inputs through the ventroanterior (VA) thalamic nucleus to the superficial cortical layers.

Action Potentials↗
PubMed1976

Actions of opiates upon single unit activity in the cortex of naive and tolerant rats.

The effect of microelectrophoretically and systemically applied opiates on neuronal discharge activity in the sensorimotor cortex of naive and morphine tolerant/dependent rats has been studied. In naive rats depression of spontaneous discharge activity was the predominant effect of low doses of phoretically applied morphine. Higher doses and repeated application frequently converted this effect into excitation. Only the depressant effect was antagonised by naloxone. Naloxone itself had no effect on spontaneous discharge activity when applied at dose-levels sufficient to antagonise the depressant effect of morphine. Levorphanol mimicked the action of morphine whereas dextrorphan was inactive. Morphine depressed the excitatory action of L-glutamate and of acetylcholine by a naloxone-antagonisable mechanism. Systemic application of Fentanyl mimicked the inhibitory effect of phoretically applied morphine upon transcallosally evoked discharge activity. The late response was markedly depressed whereas the primary response was little affected. Phoretically applied naloxone antagonised the effects of systemically applied Fentanyl. In chronically morphinised rats the depressant effect of microelectrophoretically administered morphine was almost lacking and a naloxone-resistant excitation became the predominant effect. In these animals the excitant effect of naloxone was also increased and the anti-glutamate effect and the anti-acetylcholine effect of morphine was abolished. The present data speak in favour of a postsynaptically located stereospecific receptor which mediates the inhibitory effects of opiates and which may be involved in the development of acute and chronic tolerance to these drugs.

Acetylcholine↗
PubMed1995

Unilateral grafting of fetal neocortex into a cortical cavity improves healing of a symmetric lesion in the contralateral cortex of adult rats.

Fetal neocortical tissue (ED 14) was grafted unilaterally into a cortical cavity made bilaterally in the sensorimotor cortex of adult rats. Transplantation was done immediately after the lesion (group TR0, n = 8) or with 14-day delay (group TR14, n = 8). Six rats served as lesion only controls (group LES). After long-term survival (up to 15 months) the brains were photographed and surface areas of transplant and contralateral cavities were measured by means of a graphic tablet. The results show that (a) the presence of a transplant in one lesion cavity in the cortex decrease the size of a similar cavity in the contralateral cortex and that (b) the better host transplant integration there is, the greater the effect on the contralateral lesion. No correlation between the size of the transplant and the size of the symmetric traumatic lesion was found. The ameliorating effect of the transplant on the contralateral cortical lesion size is most likely related the long-term influence of growth of trophic factors released by transplanted cells which lead to the healing of the symmetric lesion.

Animals↗
PubMed1998

Spatial and temporal evolution of neuronal activation, stress and injury in lithium-pilocarpine seizures in adult rats.

In order to follow the spatial and temporal evolution of neuronal damage, cellular activation and stress responses subsequent to lithium-pilocarpine seizures of various durations in the adult rat, we analyzed the expression of Fos protein and local cerebral glucose utilization as markers of cellular activation, HSP72 immunoreactivity and acid fuchsin staining as indicators of cellular stress and injury, and Cresyl violet staining for the assessment of neuronal damage. The expression of Fos appeared very early, 2-30 min after the onset of polyspikes and intensified during the following 4 h. Fos immunoreactivity was especially high in the hippocampus, cerebral cortex, amygdala and anterior olfactory nuclei. Local cerebral glucose utilization measured during the second hour of seizures was largely increased (350-580%) over control levels in cortical areas, amygdala, dentate gyrus, caudate nucleus and mediodorsal thalamus. HSP72 immunoreactivity never appeared earlier than 40-50 min after the onset of polyspikes, and was most prominent in hippocampal CA3 area, cerebral cortex (except the piriform cortex) and anterior olfactory nuclei. Acid fuchsin staining was maximal in the piriform cortex and the polymorphic layer of the dentate gyrus. Staining was moderate in the sensorimotor cortex and the amygdala. Neuronal damage was extensive in the piriform and entorhinal cortices, the hippocampal CA3 area and the polymorphic layer of the dentate gyrus, basal amygdala, mediodorsal thalamus and anterior olfactory nuclei. In conclusion, the present study shows that brain regions with the highest expression of Fos and the largest metabolic activation were also highly stained with acid fuchsin and most heavily damaged. Conversely, there is no clear relationship between HSP72 expression, cellular activation and neuronal damage.

Animals↗
PubMed2001

Ultrastructural evidence for differential axonal sprouting in the striatum after thermocoagulatory and aspiration lesions of the cerebral cortex in adult rats.

Thermocoagulation of pial blood vessels overlying the cerebral cortex induces an ischemic degeneration of the cortex. We have previously shown with anatomical tracing techniques that thermocoagulatory lesions of the sensorimotor cortex trigger a robust axonal sprouting of contralateral cortical neurons into the denervated striatum. Similar sprouting was not observed after acute aspiration lesions of the same cortical region. We have now examined immunostaining for the growth-associated protein (GAP)-43 at the ultrastructural level after both types of lesions. A modest increase in growth cone-like structures was observed just below the corpus callosum after both lesions. However, GAP-43-positive growth cone-like structures were markedly increased in the denervated dorsolateral striatum only after thermocoagulatory lesions. In contrast, no significant increase in growth cone immunostaining was found in the dorsolateral striatum after aspiration lesions, confirming the absence of axonal sprouting in the dorsolateral striatum in this condition. Corticostriatal inputs make asymmetric synapses with dendritic spines of striatal neurons. As expected, the density of asymmetric synapses was markedly decreased in the dorsolateral striatum after aspiration lesions. However, it was not different from control after thermocoagulatory lesions that removed the same cortical area. The density of symmetric synapses was decreased after both types of lesions at 16 but not 42 days post-surgery. These data reveal that robust axonal and synaptic remodeling can occur in the dorsolateral striatum of adult rats after ischemic lesions of the cerebral cortex and further demonstrate marked differences in the degree of anatomical plasticity induced by two different types of cortical lesions.

Animals↗
PubMed2001

Noradrenergic modulation of tactile responses in rat cortex. Current source-density and unit analyses.

This study describes the noradrenergic modulation of tactile afferent information in the sensorimotor cortex of urethane-anesthetized rats. Synaptic and spike responses to a mechanical stimulation of the hand palm were evaluated by means of current source-density analysis and unit activity recording in all cortical layers. Results showed that activation of the locus coeruleus decreased and shortened afferent synaptic excitation in supragranular, but not in deep layers. On the average, unit responses exhibited facilitated latency, moderately increased amplitude, enhanced postexcitatory inhibition and synchronization of responses across layers. The apparent paradox of this global phasic facilitation correlated with a decrease in input synaptic currents was discussed according to hypotheses which might explain its functional significance.

Animals↗
PubMed1980

[Lipoperoxidation in the hyperactive focus of rat cerebral cortex].

The possibility of participation of lipoperoxidation (LPO) in the mechanisms of development of epileptic activity in rat cerebral cortex has been shown. The appearance of epileptic activity after penicillin application to the sensorimotor cortex induced a considerable increase in the concentration of LPO products in the crude synaptosomal fraction from the hyperactive focus. Preliminary injection to rats of the antioxidant alpha-tocopherol abolished the effect of LPO activation and decreased the number of seizures recorded on the electrocorticogram in the course of the focus existence.

Animals↗
PubMed1979

Effects of diphenylhydantoin on the spontaneous activity of Purkinje, nucleus interpositus, red nucleus and motor cortex cells.

(1) Extracellular multiunit recordings were made of the spontaneous activity in cerebellar Purkinje cells, nucleus interpositus, red nucleus and sensorimotor cortex in acute cat preparations. (2) Changes in this spontaneous neural activity produced by the administration of diphyenylhydantoin (DPH) were studied. DPH was infused i.v., generally at a concentration of 2.5 mg/ml and at a rate varying from 0.08 to 0.48 mg/kg/min. Two different patterns of infusion were used: fixed time, variable rate and variable time, fixed rate. Pulsed doses were also given at intervals of 5--10 min. (3) DPH at a level of 10--20 mg/kg produces a significative initial deceleration in all structures followed by a significative acceleration in the Purkinje cells, nucleus interpositus and red nucleus as a dose of 20--30 mg/kg is reached. Higher levels caused a profound depression of multiunit activity. (4) The activation produced by DPH is oscillatory (3--5/min) in character and is composed of 'trains' which occur at a rate of 20--30/sec with very rapid discharge frequencies (600--800 Hz). (5) A direct significant correlation was found between DPH serum levels and the intravenously administered dose. The activating DPH dose (20--30 mg/kg) corresponded to serum levels of 24--32 micrograms/ml. (6) The possibility is discussed whether the anticonvulsant action of DPH may be due in part to the production of rhythmic oscillatory activity in the cerebello-rubro-olivo-cerebellar ciruit and the depression of the cerebellothalamic-cortical pathway.

Animals↗