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PubMed2006

The relevance of the corticographic median nerve somatosensory evoked potentials (SEPs) phase reversal in the surgical treatment of brain tumors in central cortex.

Tumors of the central brain cortex change the original anatomy of this important area and so an intraoperative localization of the perirolandic structures is crucial in decision concerning the way and the extent of tumor resection. The phase reversal of median nerve SEPs is an essential tool for neurosurgical procedures in and around the perirolandic gyri. This study examines the relevance of the method in a group of 62 patients having surgery of tumors in and around the central region. A success rate in obtaining the SEP phase reversal was 94%. In all groups of patients the complete resection of tumor was achieved in 58% , subtotal resection in 19% and partial or biopsy only in 23%. The long term impairment of neurological status was observed in 6% of patients. Compared to the recently published studies our results are acceptable both in completeness of tumor resection and relatively low ratio of impaired postoperative neurological deficit despite the fact, that in the majority of patients the phase reversal mapping was the only method guiding the surgical procedure. Our study supports the crucial role of the central cortex mapping using the SEP phase reversal method in the surgery for the tumors of the primary sensorimotor cortex.

Adult↗
PubMed1991

[Disorders of cerebral monoamide oxidase activity in rats after prenatal alcoholization and their correction with reduced glutathione].

Structures of the brain of rats from the offsprings of alcoholized female rats and animals given glutathione postnatally were examined for monoamine oxidase (MAO) activity by histochemistry using discrete cytospectrophotometry. A decrease of the enzyme activity in caudate nucleus neuropile, preserved up to the 60th postnatal day, an increase of the enzyme activity in neuropile of layer III of the visual cortex in 30-day-old rats from the offsprings of the alcoholized females and a lowering in layer V of the visual cortex in 60-day-old offspring were identified. There were no changes in neuropile of the sensorimotor cortex. Postnatal administration of glutathione to the animals alcoholized on an intrauterine basis resulted in complete normalization of MAO activity by the 60th postnatal day.

Alcoholism↗
PubMed1986

A protein associated with axon growth, GAP-43, is widely distributed and developmentally regulated in rat CNS.

Development or regeneration of axons in several systems is accompanied by 20-100-fold increases in the synthesis of an acidic, axonally transported membrane protein with an apparent molecular weight of 43-50,000 (Benowitz and Lewis, 1983; Skene and Willard, 1981a, b), which we designate GAP-43. We have proposed that some step(s) in axon growth require production of GAP-43, and perhaps a small number of other "growth-associated proteins," at rates much higher than those typical of mature neurons. This hypothesis predicts that virtually all neurons synthesize GAP-43 at elevated levels during normal CNS development. Here we show that a protein similar to GAP-43 from regenerating toad nerves is prominent among the newly synthesized (35S-methionine-labeled) and total (Coomassie blue-stained) proteins in neonatal rat cerebral cortex and cerebellum, suggesting that synthesis of GAP-43 is indeed a common feature of many developing neurons. Synthesis and accumulation of the protein decline an order of magnitude as animals mature. Antibodies raised against the rat cortex GAP-43 also recognize electrophoretically similar proteins from regenerating toad optic nerves and from developing hamster sensorimotor cortex, indicating that structural features of GAP-43 are conserved in evolution. Cell-free translation of polyadenylated RNA from neonatal and adult cortex suggests that developmental regulation of GAP-43 synthesis is mediated largely through changes in mRNA abundance. These observations together suggest that developmental regulation of GAP-43 gene expression may be common to most vertebrate CNS neurons. GAP-43 remains detectable at a low level in adult rat cortex, and it co-migrates on two-dimensional gels with B-50, a synaptic membrane protein which is a preferred substrate for protein kinase C in adult brains. Phosphorylation of the protein by endogenous kinase(s) in vitro is 4-7-fold greater in growth cone membranes than in mature synaptic membranes, which raises the possibility that local modification of the protein in axon terminals may be synergistic with regulation of GAP-43 synthesis in the cell body.

Animals↗
PubMed2005

Oscillatory coupling in writing and writer's cramp.

Writing is a highly skilled and overlearned movement. In patients suffering from writer's cramp, a focal task-induced dystonia, writing is impaired or even impossible due to involuntary muscle contractions and abnormal posture, which occur as soon as the person picks up a pen or within writing a few words. The underlying pathophysiological mechanisms of this movement disorder are not fully understood up to now. The aim of the present study was to unravel the oscillatory network underlying physiological writing in healthy subjects and dystonic writing in writer's cramp patients. Using whole-head magnetoencephalography (MEG) and the analysis tool dynamic imaging of coherent sources (DICS) we studied oscillatory neural coupling during writing in eleven healthy subjects and eight patients suffering from writer's cramp. Simultaneous recording of brain activity with MEG and activity of forearm and hand muscles with surface electromyography (EMG) was performed while subjects were writing for five minutes with their dominant right hand. Applying DICS sources of strongest cerebro-muscular coherence and cerebro-cerebral coherence during writing were identified, which consistently included six brain areas in both, the control subjects and the patients: contralateral and ipsilateral sensorimotor cortex, ipsilateral cerebellum, contralateral thalamus, contralateral premotor and posterior parietal cortex. Coherence between cortical sources and muscles appeared primarily in the frequency of writing movements (3-7 Hz) while coherence between cerebral sources occurred primarily around 10 Hz (8-13 Hz). Interestingly, consistent coupling between both sensorimotor cortices was observed in patients only, whereas coupling between ipsilateral cerebellum and the contralateral posterior parietal cortex was found in control subjects only. These results are consistent with the often described bilateral pathophysiology and impaired sensorimotor integration in writer's cramp patients.

Adult↗
PubMed2005

The cellular composition of the cerebral cortex of rat fetuses after fractionated low-dose irradiation.

Histological and morphometric studies were performed to address the characteristics of the morphogenesis of the sensorimotor cortex of the brain in rat fetuses subjected to fractionated gamma irradiation during the period from day 6 to day 18 of antenatal development at doses of 5, 25, 30, and 75 cGy. The results showed that fractionated irradiation at doses of 5-75 cGy had adverse effects on the processes of stem cell proliferation in the tissues of the developing cortex and also increased the intensity of cell destruction proportionally to the radiation dose. All cellular zones of the developing cortex showed increases in the absolute number of macroglial cells, which may be associated on the one hand with reactive increases in their production due to functional deficiencies and, on the other, with accelerated transformation of radial gliocytes into macroglial cells. Irradiation at doses of 5-75 cGy decreased the rate of migration of neuroblasts into the primary cortex, as shown by decreases in the numbers of cells in the neural differon in the neocortical rudiment and increases in their levels in the deep layers of the developing cortex.

Animals↗
PubMed2001

Regulating action: alternating activation of midline frontal and motor cortical networks.

OBJECTIVES: Focal electrical fields recorded over the midline prefrontal cortex have been found to index rapid evaluative decisions, including the recognition of having made an error in a speeded response task. The nature of these electrical fields and how they are related to cortical areas involved in response execution remains to be clarified. METHODS: As subjects performed a speeded response task the EEG was recorded with a 128-channel sensor array. By filtering out the large slow waves of the event-related potential, we found that the error-related negativity (Ne/ERN) arises from a midline frontal oscillation that alternates with oscillations over lateral sensorimotor cortex. Electrical source analyses were used to determine the brain sources involved in the generation of these oscillations. RESULTS: The results show that the midline and lateral oscillations have a period of about 200 ms (theta), and they are present for both correct and error responses. When an error is made, the midline error oscillation is recruited strongly, and it becomes correlated with the motor oscillation. Source analyses localized the midline error oscillation to centromedial frontal cortex and the lateral oscillation to sensorimotor cortices. CONCLUSIONS: Because of the similarity between the midline oscillation observed in the present study and frontal midline theta, the nature of the Ne/ERN may be clarified by the frontal midline theta literature. The correlation between the midline and sensorimotor oscillations suggests a possible mechanism for how midline frontal evaluative and monitoring networks contribute to action regulation.

Adolescent↗
PubMed2002

Brain metabolic changes during cigarette craving.

BACKGROUND: In functional brain imaging studies, exposure to cues related to cocaine, opiates, and alcohol in dependent individuals is associated with activation of the anterior cingulate gyrus, amygdala, orbitofrontal cortex, and dorsolateral prefrontal cortex. Craving for these substances positively correlates with activity in the orbitofrontal cortex, dorsolateral prefrontal cortex, and anterior insula. The objective of this study was to determine changes in regional cerebral glucose metabolism and correlations between craving and regional metabolism in heavy cigarette smokers exposed to cigarette-related cues. METHODS: Twenty heavy smokers (who smoked > or =20 cigarettes per day) and 20 nonsmoking control subjects underwent 2 fluorine 18-fluorodeoxyglucose positron emission tomography scans 10 days apart in randomized order: one while watching a videotape that presented cigarette-related cues and handling a cigarette, and the other while watching an educational (nature) videotape and handling a neutral object (pen). RESULTS: From the neutral to the cigarette cue scan, heavy smokers had greater increases than nonsmoking controls in relative glucose metabolism in the perigenual anterior cingulate gyrus spanning the midline. Significant positive correlations were found between intensity of craving and metabolism in the orbitofrontal cortex, dorsolateral prefrontal cortex, and anterior insula bilaterally. An unexpected positive association was found between craving and metabolism in the right sensorimotor cortex. CONCLUSIONS: Brain regions associated with arousal, compulsive repetitive behaviors, sensory integration, and episodic memory are activated during exposure to cigarette-related cues and cigarette craving. These regional brain activations and associations with craving are similar to findings with other addictive substances.

Adult↗
PubMed1987

Alterations in regional energy metabolism in rat brain produced by small and by large doses of apomorphine: possible relations to autoreceptors.

Dose-dependent changes in behavioural patterns and in local cerebral glucose utilization (LCGU) following subcutaneous application of apomorphine were measured in conscious, unrestrained rats by means of a scoring system and of the autoradiographic [C14]2-deoxyglucose technique, respectively. The behavioural patterns of akinesia, ptosis, yawning and penile erections were scored. Akinesia and ptosis were most prominent after 0.02 and 0.07 mg/kg apomorphine but not after 0.18 mg/kg. Maximal scores for yawning and penile erections were obtained after 0.07 mg/kg. LCGU was not significantly changed after 0.07 mg/kg except for decreases in the cingulate cortex and hypothalamus. Apomorphine 0.5 mg/kg decreased LCGU in the cingulate, parietal and occipital cortex, anteromedial and lateral thalamus and lateral habenula but increased it in laminae IV and VI of the sensorimotor cortex, in the parafascicular nucleus of the thalamus, and in some parts of the basal ganglia and related nuclei. Similar changes in LCGU occurred after 2.0 mg/kg apomorphine, which also increased LCGU in the ventral tegmental area. The lower dose did not produce changes in LCGU opposite to those occurring after larger doses. The data obtained with LCGU do not support the idea that behavioural effects after low doses of apomorphine are elicited by activation of dopamine autoreceptors.

Animals↗
PubMed1994

Cerebral network underlying unilateral motor neglect: evidence from positron emission tomography.

In 4 male patients (age range 50-73 years) with unilateral motor hemineglect as a sequelae of circumscribed cerebral infarction, depressions of the regional cerebral glucose metabolism (rCMRGlu) were mapped to identify the metabolically affected cerebral structures. Motor neglect was defined according to Castaigne by lack of spontaneous and pain-induced motor activity on one side of the body in the absence of paresis, pyramidal signs, and sensory loss. The depressions of the rCMRGlu as determined by positron emission tomography (PET) were found to exceed the areas of structural damage but to be restricted to the affected cerebral hemisphere. Significant mean rCMRGlu depressions followed a focal pattern involving the premotor, prefrontal, parietal and cingulate cortex, as well as the thalamus. In correspondence to the lack of significant mean rCMRGlu depressions in primary sensorimotor cortex, basal ganglia, and cerebellum the cortico-spinal pathway was spared as indicated by preserved magnetic evoked motor potentials. Our data provide evidence suggesting that motor hemineglect is a disturbance in a cerebral network of higher order cortical areas subserving motor activity in the presence of an intact motor cortical output system.

Aged↗
PubMed2004

Low frequency corlico-muscular coherence during voluntary rapid movements of the wrist joint.

Rapid voluntary point-to-point wrist tracking movements are generated by the co-operative action of a large number of wrist muscles activated in a stereotypic pattern. This pattern is composed of a two burst sequence occurring in synergist and antagonist muscles. The time course and duration of these bursts are relatively fixed but the burst magnitude in any one muscle varies in relation to the direction of movement and the preferred directional tuning characteristic of the muscle. This creates a highly adaptive method for generating fast movements to different positions in space. In this study we have examined the extent to which this adaptive burst behaviour can be associated with activity changes occurring in the contralateral motor cortex. Time dependent coherence estimates were obtained from simultaneous recordings of the electroencephalogram (EEG) made from the contralateral sensorimotor cortex and the electromyogram (EMG) from various wrist flexor and extensor muscles during fast point-to-point wrist tracking movements. Using the onset of movement as a trigger, event related coherence estimates reveal the presence of short lasting periods of low frequency (<12 Hz) coherence during the execution of fast wrist movements. The onset and duration of the periods of low frequency coherence vary with direction of movement and the temporal burst profile of a particular muscle's EMG activity. It is therefore likely that a significant low frequency activation of the motor cortex plays a part in the generation of the EMG burst patterns that underpin rapid point-to-point movements of the human wrist.

Cerebral Cortex↗
PubMed1999

Spinal and brain circuits to motoneurons of the bulbospongiosus muscle: retrograde transneuronal tracing with rabies virus.

Retrograde transneuronal tracing with rabies virus from the left bulbospongiosus muscle (BS) was used to identify the neural circuits underlying its peripheral and central activation. Rats were killed at 2, 3, 4, and 5 days post-inoculation (p.i.). Rabies immunolabelling was combined with immunohistochemical detection of choline acetyltransferase and oxytocin. Virus uptake was restricted to ipsilateral BS motoneurons (2 days p.i.). The onset of transfer (3 days p.i.) visualized interneurons in the dorsal grey commissure (DGC), intermediate zone, and sacral parasympathetic nucleus (SPN), mainly in DGC at L5-S1, and revealed synaptic connections between BS and external urethral sphincter motoneurons. At 4 and 5 days p.i., higher-order interneurons were labelled in other spinal areas and segments. Supraspinal labelling initially involved only Barrington's nucleus, nucleus reticularis magnocellularis, and paragigantocellularis lateralis (4 days p.i.). Later, labelling extended to other populations traditionally associated with control of sexual activity and micturition (periaqueductal grey, paraventricular nucleus, medial preoptic area, prefrontal cortex), but also indicated the intervention of somatic descending motor pathways (vestibulospinal and reticulospinal neurons, "hindlimb" regions of sensorimotor cortex and red nucleus) and cerebellar nuclei in multisynaptic innervation of the labelled motoneurons. Dual color immunofluorescence disclosed multisynaptic links between these motoneurons and thoracolumbar medial sympathetic (choline acetyltransferase-immunoreactive) neurons. In contrast, preganglionic neurons in SPN and most oxytocinergic neurons in paraventricular hypothalamic nucleus remained unlabelled, suggesting that parasympathetic and somatic outflow to pelvic organs are probably controlled by separate interneuronal populations and that oxytocinergic spinal projections are more likely to influence sacral autonomic rather than somatic outflow.

Animals↗
PubMed1989

[The collateral branching of the axons of efferent neurons in the cat parietal cortex].

Collateral branching of efferent neurons' axons in the cat parietal associative cortex was studied with intracellular recording of antidromic activity. Specific features of the axon collaterals projecting onto the sensorimotor cortex, pontine nuclei proper and red nucleus, were revealed and described. Information arriving from the parietal cortex simultaneously at the above two motor structures suggests their interrelationship to be actualized through the axon collaterals of efferent neurons. This kind of functional interrelationship of the structures via axon branching of efferent neurons of the parietal cortex provides synchronous arrival of signals at the structures participating in motor integration.

Animals↗
PubMed1981

Interanalyzer two-way neuronal connections during alimentary conditioning in cats.

Milk conditioned reflexes to low frequency electrostimulation of optic tracts was examined in four cats. Multineuronal activity from visual and sensorimotor cortical regions was recorded under conditions of chronic implantation. Intra- and interanalyzer interneuronal connections were statistically analyzed by constructing crosscorrelograms. The comparison of the results of interneuronal interaction in untrained and trained animals showed an increase of one-way and two-way connections both of intra- and interanalyzer types. Neurons characterized by intermediate amplitude spike, more than other neurons, changed their network properties and were enriched by incoming and outgoing connections in both visual and sensorimotor cortex of the trained animals. An increase in the total number of interneuronal connections after acquisition was due to an increase of connections from the sensorimotor to the visual analyzer.

Animals↗
PubMed1992

[Effects of magnesium and nickel ions on penicillin-induced focal epileptic activity in the cerebral cortex of rats].

In experiments on freely moving male Wistar rats on the model of penicillin-induced focal epileptic activity (EA) (the application onto the sensorimotor cortex of a filter paper soaked with benzylpenicillin sodium salt solution) it was shown that addition of MgSO4 (series 1) and NiCl2 (series 2) into the solution of penicillin significantly weakened EA. The combination of Mg2+ and Ni2+ with penicillin (series 3) produced a more significant suppression of EA as compared with separate application of the above-mentioned ions: the latency period of appearance of interictal discharges (IID) increased, the frequency and amplitude of IID decreased much more, no ictal discharges appeared in any animal, the duration of epileptic foci reduced to a much greater extent. This effect can be explained by the blockade of Ca current by the above-mentioned ions. One can suppose that the amplification of antiepileptic effects of combined action of Mg2+ and Ni2+ was due to an increase in the number of blocked voltage-dependent and NMDA-operated calcium channels.

Animals↗
PubMedDate not supplied

State of synapses of the cortex of cerebral hemispheres on gamma-irradiation.

In adult rats with developing neurological disorders we detected destructive changes in most of the synapses of the brain sensorimotor cortex 1.6-4.3 h after a single dose of gamma-irradiation (200 Gy). All functionally important parts on the axonal and dendritic sides of the synapses had undergone changes: mitochondria, synaptic vesicles, pre- and postsynaptic membranes, synaptic complexes, and subsynaptic consolidations, axonal and dendritic plasma, and their inclusions. These changes possibly cause disconnection of the neurons and provide a structural basis for neurological deficiencies following a high substantial ionizing radiation.

Animals↗
PubMedDate not supplied

The reactivity and interaction of neurons of the cerebral cortex of rats in the presence of the microiontophoretic action of acetylcholine in a model negative learning situation.

The activity of 46 pairs of neurons in the sensorimotor cortex of the brain of rats during multiple (up to 60) brief microiontophoretic applications of acetylcholine (ACh) was investigated by means of the method of multicellular recording, with subsequent division into separate impulse streams. It was demonstrated that neurons with high-amplitude spikes have a lower average frequency of discharges in comparison with low-amplitude [neurons]. It was established that cells located adjacent to one another exhibit responses in 63% of cases which are similar in their component makeup; the majority of these responses are inhibitory-excitatory and excitatory. Analysis of the dynamics of the structure of the cross-interval histograms plotted for pairs of cells on the basis of the data of their initial activity, as well as activity in the baseline, and upon termination of the action of ACh, attest to the relative invariability of the excitatory connections between the cells and a possibility of some increase in the efficiency of the inhibitory connections under the conditions of the manifestation of the dynamics of responses to ACh of habituation type by one of the cells.

Acetylcholine↗
PubMed1986

[Self-sustaining rhythmic activity of the "peak-wave" type and responses of neuronal and glial cells of the sensomotor cortex of the cat].

In acute unanesthetized immobilized cats a sequence of fast hyperpolarization and long-lasting depolarization was found in pyramidal tract neurons of the sensorimotor cortex during tetanic stimulation (8-14/s for 10 s) of the ventro-postero-lateral nucleus of the thalamus. During long-lasting depolarization after cessation of stimulation self-sustained rhythmic paroxysmal depolarizing membrane potential shifts appeared which were terminated by long-lasting hyperpolarization. In glial cells only depolarization was observed during stimulation as well as during self-sustained "spike-and-wave" rhythmic activity. Hyperpolarization in glial cells appeared only after its termination in neurons. It is suggested that the long-lasting changes in the membrane potential of cortical elements may play a particular role in formation and cessation of "spike-and-wave" rhythmical activity.

Animals↗
PubMedDate not supplied

[Responses of sensomotor cortex neurons of rats to stimulation of the midbrain reticular formation].

High frequency stimulation of the mesencephalic reticular formation produces significant inhibition of neuronal activity in the sensorimotor cortex, the effect being equally observed in both hemispheres. In case of low frequency stimulation, marked difference was observed between the reaction of ipsi- and contralateral neurons. Under these conditions, contralateral neurons produce mainly facilitation responses. In both hemispheres evident predominance of tonic effects was observed which revealed itself in the continuation of the reaction in the poststimulation period. Single shocks applied to the midbrain reticular formation elicited in the cortex the evoked potentials of two types: one with a constant and the other with varying latent periods. The former exhibited a latency of 4-18 msec. Responses with varying latencies were predominant. In general, latent periods were longer in contralateral hemisphere.

Animals↗