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PubMedDate not supplied

Influence of "animal hypnosis" on the motor polarizational dominant in rabbits.

The influence of the state of "animal hypnosis" in rabbits on the course and preservation of the motor polarizational dominant created by the action of a direct current anode on the region of the sensorimotor cortex was investigated. The mechanogram of both forelimbs was recorded. It was demonstrated that the state of "animal hypnosis" induced against the background of the optimum of the dominant inhibits the motor reaction of the "dominant" limb to sensory test stimuli. This inhibition is maintained for a long time, up to two to four days. The motor polarizational dominant does not extinguish under the influence of "animal hypnosis," but is inhibited; after the extinction of the traces of the "hypnosis," the motor dominant reaction recovers under the influence of sensory test stimuli alone, without the repeated use of the direct current.

Animals↗
PubMed2000

Hypertrophic synapses as a factor of formation of persistent pathological centers in the brain in the late postresuscitation period.

Clinical death was modelled on albino rats. Synapses in the molecular layer of the cerebral sensorimotor cortex were investigated 1, 2, 3, 4, 5, 6, 7, 8, and 9 months postresuscitation. The total density of synapses peaked and the number of hypertrophic and perforated contacts increased 4, 7, and 9 months after resuscitation. The role of increased number of hypertrophic and perforated contacts in the pathogenesis of postresuscitation encephalopathy is discussed.

Animals↗
PubMedDate not supplied

Coherence analysis of electrical activity in the rabbit brain during the process of substitution of dominants.

Coherence analysis was used to study intercenter relationships between biopotentials in the sensorimotor cortex (forelimb and blink representation areas) and the visual cortex in both hemispheres and the ventrolateral nucleus of the thalamus (VPL) of the left and right thalami during the formation of a motor defensive dominant (electrical stimulation of the limb skin) on a background of an induced (by stimulation of the cornea with an air jet) blink dominant. Characteristic electrophysiological measures of the dominant state (increases in the mean coherence level of potentials in the delta frequency range in structures involved in the functional defensive limb reflex system), along with the absence of behavioral manifestations of the motor dominant in the blink dominant, indicated that a cryptic potential dominant focus was created in the CNS in these conditions, and that this affected ongoing animal activity.

Aggression↗
PubMedDate not supplied

Electrophysiological characterization of the functional state of the brain in mental disturbances in workers involved in the clean-up following the Chernobyl atomic energy station accident.

Studies were carried out on 150 workers with mental disturbances, who had been involved in the clean-up of the Chernobyl atomic energy station accident. Visual and computer analyses of EEG traces from 43 workers were compared with traces from 17 healthy subjects, and the comparison revealed that the most common features in workers were disorganization of the alpha-rhythm and strengthening of beta-1-activity in the sensorimotor cortex. In neurosis-like syndromes (13 patients), there was a significant increase in the power of the alpha-rhythm in the anterior parts of the cortex; in psycho-organic states, power as significantly reduced (especially in the left hemisphere). Contributing to the greater proportion of flat EEG traces in patients with psycho-organic syndromes as compared with other groups of patients. Most patients among the clean-up workers had increased assimilation of flashing light rhythms and weakening of non-specific and skin galvanic responses to a light stimulus. It was concluded that systemic CNS changes occurred in patients from the clean-up worker groups, especially in those with psycho-organic syndrome.

Adult↗
PubMedDate not supplied

Effect of stimulation of the lateral hypothalamus on the correlation of neuron spike activity in the rabbit neocortex.

Cross-correlation and autocorrelation histograms were constructed with the aim of studying correlated spike activity of neurons in the visual and sensorimotor regions of both hemispheres of the rabbit brain before and after stimulation of the right and left lateral hypothalamic regions, which generates food-motivated responses. Stimulation of the left hypothalamus produced larger rearrangements in correlated neuron firing than stimulation of the right hypothalamus. Stimulation of the left hypothalamus, unlike that of the right hypothalamus, was followed by significant increases in the numbers of pairs of left hemisphere neocortical neurons with linked activity, and also induced the sequential firing of neurons in a particular defined order: sensorimotor cortex cells fired first, followed by visual cortex neurons after delays of up to 120 msec. It is concluded that cortical interhemisphere asymmetry in conditions of hunger is associated with nonuniform functioning of the right and left lateral hypothalamic regions.

Animals↗
PubMedDate not supplied

Cytochemical parameters of synaptic neurons in rats with different abilities to learn a food-procuring habit.

The characteristics of protein metabolism associated with cognitive activity were studied in neurons of layers III and IV of the sensorimotor cortex of rats, using two groups of Wistar rats. Regardless of the success of learning, information loading was most clearly reflected in the associative neurons of layer III. In rats with poor learning ability, these neurons showed increases in nuclear and cytoplasmic size, along with increases in protein concentration and content. The clearest changes in efferent neurons (layer V) were increases in the area and protein content, occurring only in the cytoplasm. In rats with good learning outcomes, all cytochemical parameters responded to information loading with decreases in layer III and increases in layer V protein contents and concentrations, affecting both the cytoplasm and nucleus. The question of whether the vector of changes in neuronal protein metabolism in response to information loading can be regarded as a measure of the individual features of higher nervous activity is discussed, as is the question of whether the magnitude of these changes is a measure of the complexity of a cognitive task.

Animals↗
PubMed2000

Cytochemical characteristics of the brain in rats differing in active avoidance learning ability.

Brain structures were examined in two mouse strains differing in active avoidance learning in a shuttle box. Protein content and concentration, area of the cytoplasm and nuclei of neuron in layers III and V of the sensorimotor cortex were higher in rats with high learning ability. The detected morphochemical differences between the same brain structures of rats with high and low learning capacity can be attributed to this capacity.

Animals↗
PubMed1986

Mechanisms contributing to sparing of function following neonatal damage to spinal pathways.

When spinal pathways are damaged in newborn animals and their behavior is examined in adulthood, motor function is superior to that seen in animals in which the same lesion was made in adulthood. This is the infant lesion effect. After neonatal sensorimotor cortex ablation, spinal hemisection, or spinal transection, sparing of contact placing is observed; in adults, all three lesions abolish contact placing permanently. The anatomical correlates of the infant lesion effect are different in each case. After neonatal unilateral cortical ablation, an exuberant crossed corticorubral pathway from the other cortex fails to retract (as it does normally), giving the remaining cortex a path for mediating contact placing. After neonatal spinal hemisection, late-developing corticospinal axons take an aberrant course around the lesion and mediate contact placing. After neonatal transection, the spinal inhibitory GABA-ergic system fails to develop to a normal extent. This may result in abnormal enhancement of spinal reflex pathways, especially since some dorsal roots increase their input after that lesion. Thus, a number of factors may influence the outcome of damage to the developing nervous system.

Age Factors↗
PubMed2005

[Functional magnetic resonance imaging and antipsychotics. Overview and own data].

Recently, there has been growing interest in using functional magnetic resonance imaging (fMRI) for the evaluation of psychopharmacological drugs. fMRI studies in healthy human volunteers and psychiatric patients focus on cerebral activity following acute drug administration (single challenge) and on adaptive effects on neural networks due to long-term medication. In our own fMRI studies, the effects of olanzapine or amisulpride in never treated or medication-free schizophrenic patients using robust motor, visual, and acoustic tasks was longitudinally examined. In agreement with previous reports in the literature it could be shown that, in contrast to traditional neuroleptics, atypical drugs do not decrease the activation of the sensorimotor cortex but rather normalize the reduced frontoparietal activation as well as the neuropsychological test results. This encourages the assumption that atypical antipsychotics seem to support the recovery or normalization of frontoparietal brain dysfunction in schizophrenia. However, with these new opportunities additional methodological considerations and limitations emerge.

Antipsychotic Agents↗
PubMed2003

An electron microscopic examination of the corticospinal projection to the cervical spinal cord in the rat: lack of evidence for cortico-motoneuronal synapses.

We investigated whether direct, cortico-motoneuronal connections are present in the rat, using both light microscopic and electron microscopic techniques. Corticospinal fibres were labelled using the anterograde tracer, biotinylated dextran-amine (BDA), which was injected into forelimb sensorimotor cortex. Motoneurons were retrogradely labelled after injection of cholera toxin subunit B (CTB) into forelimb muscles, contralateral to the injected hemisphere. Terminals of peripheral afferent fibres, which were also labelled by CTB, were easily distinguishable from, and much larger than, BDA-labelled corticospinal terminals. At the light microscope level, corticospinal terminals were found in all laminae contralateral to the injection site, most extensively in laminae VI and VII of cervical segments C5-C8. Although labelling in the ventral horn (lamina IX) was present, it was extremely sparse. A total of 47 corticospinal synapses were studied at the electron microscope level; most of these were in lamina VII and the majority (35/47; 74%) made axo-dendritic contacts with asymmetrical synapses; one made an axo-somatic synapse, and in the remaining 11 cases no postsynaptic structure could be identified. All corticospinal terminals contained spherical boutons. Serial sectioning of eight BDA-labelled corticospinal boutons in lamina IX revealed that most (seven out of eight) did not make synaptic contacts with any neuronal structure, and none made any contact with adjacent dendrites of CTB-labelled motoneurons. Thus these results provide no positive ultrastructural evidence for direct cortico-motoneuronal synaptic connections within lamina IX between corticospinal axon boutons and the proximal dendrites of forelimb motoneurons. The results confirm other lines of evidence suggesting that such connections are not present in the rat.

Afferent Pathways↗
PubMed2005

Effect of body weight support on cortical activation during gait in patients with stroke.

Treadmill training with body weight support (BWS) was shown to improve locomotion after stroke. We investigated whether BWS affected cortical activation during gait using an optical imaging system. In six patients with subcortical stroke, BWS lowered activation in the sensorimotor cortex (SMC) as assessed by task-related changes of oxygenated hemoglobin levels (P<0.01). The changes of SMC activation correlated with those of cadence (P<0.05). Improvement of asymmetry in SMC activation also correlated with improvement of asymmetric gait (P<0.05). In five age-matched controls, BWS increased overall activation (P<0.05) but did not modify gait parameters and there was no correlation between gait parameters and SMC activation. It is suggested that BWS might improve efficacy of SMC function in patients with stroke.

Adult↗
PubMed2006

The effects of vitamin E on penicillin-induced epileptiform activity in rats.

Epilepsy is a disorder characterized by recurrent seizures, which can increase the content of reactive oxygen in the brain. Active oxygen free radical scavengers such as ascorbic acid or alpha-tocopherol (vitamin E) might prevent epilepsy. A variety of animal seizure models exist which help to document the effects of vitamin E and specify its action. In this study, we have evaluated dose-dependent effect of alpha-tocopherol on penicillin-induced epileptiform activity, analyzed by electrocorticogram (ECoG). The epileptiform activity was induced by microinjection of penicillin into the left sensorimotor cortex. Thirty minutes after penicillin injection, 100, 300, or 500 mg/kg of alpha-tocopherol was administrated intramuscularly (i.m.). alpha-Tocopherol (100, 300, or 500 mg/kg) alone did not significantly change the spike amplitudes in non-penicillin pretreated control animals. alpha-Tocopherol of 300, or 500 mg/kg significantly decreased the frequency of epileptiform activity in the penicillin-pretreated animals. The low dose of alpha-tocopherol (100 mg/kg) did not significantly change either amplitude or frequency of epileptiform activity. alpha-Tocopherol of 500 mg/kg i.m. was the most effective dose in changing of frequency on penicillin-induced epileptiform activity. The anti-convulsant effects of alpha-tocopherol appeared 80, 60, 30 min after alpha-tocopherol injection in 300, 500, and 3 day vitamin E supplemented groups. These data indicate that alpha-tocopherol decreases the frequency of penicillin-induced epileptic activity.

Animals↗
PubMed2006

Loss of interhemispheric inhibition in patients with multiple sclerosis is related to corpus callosum atrophy.

Axonal injury and loss in the corpus callosum (CC) is characteristic of the pathology of multiple sclerosis (MS). Functional magnetic resonance imaging (fMRI) potentially allows neurophysiological consequences of this interhemispheric axonal loss to be defined quantitatively. Here we have used 3T fMRI to study the activation in the contralateral primary sensorimotor cortex and deactivation (mediated by transcallosal tracts) in the homologous ipsilateral region in 14 patients with MS and in 14 matched healthy controls during a simple hand-tapping task. Both healthy controls and MS patients showed similar activation in the motor cortex contralateral to the hand moved, but the patients showed a significantly smaller relative deactivation in the ipsilateral motor cortex (P = 0.002). The difference was accounted for by the sub-group of MS patients who previously had impairment of motor function of the hand tested (MS-phd). The CC of the whole patient group was significantly thinner than for the controls (P = 0.001). Atrophy of the CC was correlated with loss of deactivation for the whole patient group (r = -0.50, P = 0.035), but particularly for MS-phd (r = -0.914, P = 0.004). Interhemispheric physiological inhibition thus is impaired in patients with MS, potentially contributing to impairment of motor control. This work suggests one way in which FMRI monitoring of the transcallosal interactions in motor cortex could become a tool for evaluation of therapies that may enhance function in reversibly impaired pathways.

Adult↗
PubMed2006

Reduced functional activation after fatiguing exercise is not confined to primary motor areas.

We have previously shown that following a period of unimanual fatiguing exercise, there is a reduction in primary sensorimotor cortex (SM1) activation with movement of either the fatigued or the non-fatigued hand by Benwell et al. (Exp Brain Res 167:160-164, 2005). In the present study we have investigated whether this reduction is confined to motor areas or is more widespread. Functional imaging was performed before and after a 10-minute fatiguing exercise of the left hand (30% of maximum handgrip strength) in seven normal subjects (4 M, mean age 25 years). The activating task was a handgrip against a low resistance (1 kg) in response to a visual cue (chequerboard reversal every 2 +/- 0.5 s). We compared activation in SM1, supplementary motor area (SMA), cerebellum (CB) and primary visual cortex (V1) before and after the fatiguing exercise. After exercise, contralateral SM1 activation was reduced by 33% (P < 0.05) compared to baseline for the fatigued hand and by 49% for the non-fatigued hand (P < 0.05). A similar pattern was seen for the bilateral SMA and ipsilateral CB following exercise (45 vs. 50% for SMA; 30 vs. 35% for CB; fatigued versus non-fatigued). Activation was also reduced in V1 but to a lesser extent than in motor areas (19 vs. 24%; fatigued versus non-fatigued). These results show that although the reduced functional activation during the recovery period after fatiguing exercise is more marked in motor areas, it also extends to non-motor areas such as the visual cortex, suggesting that there are more widespread changes in cerebral haemodynamic responses after fatigue.

Adult↗
PubMed1998

5-Hydroxytryptamine modifies neuronal responses to glutamate in the red nucleus of the rat.

The effects of 5-hydroxytryptamine (5-HT) on the responses of red nucleus (RN) neurones to glutamate (glu) and its agonists were studied using a microiontophoretic technique in anaesthetised rats. Extracellular unitary recordings of RN neuronal activity showed that 5-HT application induced a significant and reversible depression of glu-evoked excitations in 85% of the RN units tested. This effect was independent of the action of the amine on background firing, which appeared enhanced in the majority of cases but was either depressed or uninfluenced in other cases. Microiontophoretic 5-HT also depressed the excitatory responses evoked in RN neurones by electrical stimulation of sensorimotor cortex. Methysergide application, which prevented the enhancing effects of 5-HT on the background firing, was scarcely effective in antagonising the depression of glu responses. In contrast, the serotonergic effects on the glu responses were reduced by the iontophoretically applied antagonist of 5-HT1A receptors, NAN-190. Microiontophoretic 5-HT was also able to influence the neuronal responses evoked by glu agonists quisqualate (quis) and N-methyl-D-aspartate (NMDA), acting on non-NMDA and NMDA receptors respectively. In fact 5-HT depressed quis-evoked excitations and induced mixed effects on NMDA responses, which were reduced in 45%, enhanced in 34% and unmodified in 21% of the units tested. These results suggest that 5-HT is able to modulate the motor glutamatergic input to RN by acting mostly on non-NMDA receptors. The modulation of non-NMDA and NMDA receptors by 5-HT in the RN appears significant and its functional meaning is discussed.

Animals↗
PubMed1998

Group III metabotropic glutamate receptor agonists modulate high voltage-activated Ca2+ currents in pyramidal neurons of the adult rat.

In pyramidal neurons of the rat sensorimotor cortex, we have investigated the modulation of high voltage-activated calcium currents by agonists at group III metabotropic glutamate receptors (mGluRs). l-2-Amino-4-phosphonobutyrate (l-AP4) and l-serine-O-phosphate (l-SOP) reduced calcium currents in the vast majority of cells isolated from the adult animal. Interestingly, this modulation was negligible in the young animals (2-14 postnatal days), becoming prominent only after full development (more than 21 days). The efficacy of l-SOP mimicked l-AP4 in reducing calcium currents. Yet, l-SOP produced saturating responses at about 3 microM and significant modulation at nanomolar concentrations (EC50=923 nM). The voltage-dependence of the group III mGluR-mediated responses was evaluated by comparing the inhibition of "standard" and "facilitated" conductances. On the calcium currents facilitated by depolarizing prepulse, 3 microM l-SOP produced a mean 13.4% inhibition compared with 19.6% in control condition, supporting the proposition that part of the inodulation was voltage-dependent. The calcium current inhibition caused by the activation of group III metabotropic glutamate receptors was only partially sensitive to omega-conotoxin GVIA, but largely inhibited by omega-agatoxin IVA, at concentrations (100 nM) known to block P- and Q-type channels. Conversely, the dihydropyridine antagonists nifedipine and nimodipine (50-500 nM) failed to prevent the group III mGluR-mediated response in the majority of tested cells (more than 65%). Furthermore, the long-lasting tail promoted by the inclusion of the dihydropyridine agonist Bay K 8644 was not consistently affected by l-SOP and l-AP4. These findings imply that the observed modulation involves different channel subtypes, namely N- and P- or Q-type channels, and suggests that group III mGluRs play an important role in the intrinsic and synaptic functions of adult cortical pyramidal neurons.

Aging↗
PubMed2000

Functional reorganisation of the corticomotor projection to the hand in skilled racquet players.

While it is known that relatively rapid changes in functional representation may occur in the human sensorimotor cortex in short-term motor-learning studies, there have been few studies of changes in organisation of the corticomotor system associated with the long-term acquisition of motor skills. In the present study, we have used transcranial magnetic stimulation (TMS) to investigate the corticomotor projection to the hand in a group of elite racquet players, who have developed and maintained a high level of skill over a period of many years, and have compared the findings with those in a group of social players and a group of non-playing control subjects. Increased motor-evoked-potential (MEP) amplitudes and shifts in the cortical motor maps for the playing hand were found in all of the elite players and cortical motor thresholds were reduced in some players, whereas in the social players all parameters were within the normal range. The findings in the elite players are interpreted as being indications of a process of functional reorganisation with the motor cortex or corticomotor pathway that are associated with the acquisition and retention of complex motor skills.

Adult↗
PubMed2006

Cortical areas functionally linked with the cerebellar second homunculus during out-of-phase bimanual movements.

We used functional magnetic resonance imagery (fMRI) to study cortical activation during index finger-thumb opposition of both hands using in-phase and out-of-phase modes. In-phase movements activated the sensorimotor cortex. During out-of-phase movements, activations were also observed in the supplementary motor area (SMA), in the cingulate motor area (CMA) and, less frequently, in the anterior cingulate cortex (ACC). As we have previously shown and confirmed in the present study, the same out-of-phase bimanual movements specifically activate the cerebellar second homunculus, leading us to postulate that the cerebellar second homunculus and medial wall motor areas participate in a circuit specifically involved in timing complex movements.

Adult↗