Neurophysiology最新文献

Either a hand movement or a gesture appears to be worthy of study regarding industrial requirements for operators who have to accomplish multiple activities with a high recurrence. We propose a pattern recognition system for the categorization of hand motions based on the technique of linear discriminant analysis (LDA) of EMG phenomena. Because LDA is a statistical approach allowing for simultaneous assessment of the differences between two or more groups regarding many variables or sets of variables, it is being used for accurate evaluation of the muscle-force relationship. In this investigation, we used surface electromyogram (sEMG) data collected from ten volunteers. sEMGs were recorded via two muscle channels (m. flexor digitorum and m. extensor digitorum). Matlab® was used to extract features and other necessary parameters, and further statistical analysis in the form of pairwise comparisons was performed using SPSS®. An efficiency of 88.6 and 87.1% was provided by the proposed system regarding channel 1 and channel 2 muscle locations respectively. Further, these results may have an essential value for researchers actively involved in hand prosthetic design.

In rats with experimental intracerebral hemorrhage, we studied reactions of astrocytes, their involvement in the formation of the glial scar, and modifications of the above reactions induced by the introduction of large doses of dexamethasone. The dependence of the state of the glial scar on the size of the hemorrhage and the severity of the inflammation was observed. Dexamethasone introduction led to a sharp increase in the expression of GFAP and an increase in the specific density of astrocytes around the hemorrhage zone. The dynamics of astrogliosis under such conditions no longer depended on morphological parameters of the hemorrhage in the brain. Despite new data on the effect of dexamethasone on the reactive astrogliosis in the model of intracerebral hemorrhage, the question of changes in the morphological type of the scar within the perihematomal area (glial scar or membrane) requires further research.

Spontaneous neural regeneration may occur in peripheral nerve injury after nerve resection with a relatively short gap, whereas regeneration does not occur after nerve resection with a relatively long gap. We have examined spontaneous neural regeneration after severe nerve injury modeled by the resection of a relatively long nerve segment in adult rats. After hypoglossal (XII) nerve resection at lengths of 0, 3, 6, 9, or 12 mm, motoneurons in the XII nucleus were labeled with 1,1’dioctadecyl-3,3,3’,3’-tetramethylindocarbocyanine perchlolate (DiI); the latter was multiply injected into the tongue 12 weeks after the nerve resection. In the 0 mm length nerve-resected rats that were transected, the numbers of DiI-labeled XII neurons were as high as that in the control. In the 3 mm nerve-resected rats, the number of DiI-labeled neurons was slightly less than that in the control, and the numbers were clearly smaller than that in the control and in the 6 and 9 mm nerve-resected rats. Moreover, in the 12 mm nerve-resected rats, the number of DiI-labeled neurons was minimal, or only single such cells were observed. We conclude that spontaneous neural regeneration of the XII motoneurons might occur after moderately severe XII nerve injuries with a long nerve gap.

Previously, we proposed a “thermodynamic” model (T-model) in an attempt to analyze temporal dynamics of the central commands (CCs) coming to the muscles in the course of forelimb movements in humans. The model used electromyography (EMG) data and was tested on a simplified geometric simulation of a human arm with a fixed shoulder joint in the case of parafrontal hand movements under the action of tangential loads. The T-model is based on equations that determine the relationship between infinitesimal changes in the muscle force and length, which, by analogy with the principles of classic thermodynamics, are taken as exact differentials. Thus, our study represents the further development of the T-model, taking into account the CCs coming to the elbow joint muscles, belonging to the subject with known biomechanical parameters of his arm identified via magnetic resonance imaging (MRI). When considering circular planar movements of the subject’s hand against the background of tangential loads, symmetrical sinusoidal force waves develop in the muscles, and the CC waves acquire asymmetric shapes. The proposed method of the equalization/normalization procedure in the T-model allows us to formally consider the inverse transformation of the symmetric force waves into asymmetric CCs, which are the root cause of force generation. This approach was found to be quite effective in describing hysteresis differences of the CCs related to oppositely directed test movements. To analyze these differences using the T-model, we propose a method using multiplicative or additive correction terms to be applied to the muscle stiffness, or force velocity, respectively. The further development of the T-model is discussed concerning the real experimental practice.

Physiological and pathophysiological aspects of the functioning of the cerebral system (hypothalamus and cerebral epiphysis) providing the circadian rhythm in humans are described with special attention to the involvement of disorders in this system in the pathogenesis of some neurodegenerative diseases and epilepsy.

Problems of the engagement of collapsin-response mediator protein 2 (CRMP2) in the induction of epileptic seizures and the interrelationship between epileptic activity and the back-remodeling process in brain neurons were examined. The first part of the study was carried out in clinics. Chronic patients of both sexes (pre-puberty age) formed the patient group (n = 20), whereas 15 healthy persons of the same age served as the control group. The blood samples were taken from the patients within the free-of- seizure timeframe, and the platelets and serum were saved. The levels of CRMP2 and βIII tubulin were evaluated in the patient platelets, and the levels of natural anti-CRMP2 autoantibody and nerve growth factor (NGF) were evaluated in the serum samples with an indirect ELISA test. Downregulation of CRMP2 and βIII tubulin in the platelets, sharp downregulation of natural anti-CRMP2 autoantibody, and upregulation of NGF in the serum samples were revealed. In the second (experimental) series, epileptic seizures were induced in the Chinchilla male rabbits through penicillin microapplication into the basolateral portion of the amygdala. Microapplication of CRMP2 into the brain lateral ventricle 4–5 min later provided termination of epileptic seizures. The effect of the intracerebral administration of polyclonal anti-CRMP2 antibody to stress-tolerant Wistar male rats on their tolerance to audiogenic stress (90–120 dB, 3 min) was also examined. Antibody administration did not decrease the tolerance of the stress-tolerant rats to audiogenic stress and did not elicit epileptic seizures in them. The results obtained give grounds to formulate a conclusion on the negative relationship between the CRMP2 level and both the induction of epileptic seizures and the process of back remodeling in the brain neurons.

In a group of healthy adult male albino rats (n=6), we measured pain thresholds under conditions of electrocutaneous stimulation of the limbs (in a chamber with an electrified floor). The animals were subjected to the action of a modeled baroacoustic wave (excess pressure 26–36 kPa) leading to mild blast-induced traumatic brain injury (bTBI). It was found that such a trauma resulted in a long-lasting (up to four weeks) decrease in the above threshold (i.e., in an increase in the sensitivity of the nociceptive system) estimated according to the minimum intensity (μA) of 50-Hz alternating stimulation current evoking a pain-related behavioral response (vocalization). The pain threshold was measured at repeated stimulations of the increasing intensity of animals under light inhalation (halothane) anesthesia. There were reasons to believe that such an effect included two phases, an early (up to three days) and a later more long-lasting phase. The dynamics of the pain threshold in the bTBI group of rats were compared with those in the groups of fully intact rats (intact group) and rats subjected to the procedures of inhalation anesthesia and soft fixation but with no action of the baroacoustic wave (sham group). It is concluded that even mild blast-related trauma leads to significant long-lasting changes in the functioning of the nociceptive and antinociceptive brain neuronal systems, especially in their opioid-mediated components. These shifts develop due to energy deficiency, oxidative stress, and the accompanying mitochondrial damage. Such findings confirm suppositions that blast trauma-related changes in the cerebral opioid systems play a considerable role in the disorders of brain cognitive functions disturbed because of a blast-induced brain injury.

As is supposed, dysfunction of the autonomic nervous system may be involved in the pathogenesis of myasthenia gravis (MG). Disorders of the pupillomotor, orthostatic, vasomotor, and gastrointestinal systems may cause symptoms in MG. Among such symptoms, dysphagia has not yet been reported. However, this phenomenon can be a frequent symptom in patients with MG. We have examined 19 patients with class 1–2b MG (by classification of the Myasthenia Gravis Foundation of America) and 19 healthy volunteers. The existence and severity of dysphagia were characterized using clinical screening tests, manometry and endoscopy, electroneuromyography, and electrocardiography. Significant differences were found between groups of patients with dysphagia and with normal swallowing in Eat-10 and fiberoptic endoscopic evaluation of swallowing scores (P=0.001 in both cases). Between these groups, there were also significant differences in the active standing test and sympathetic skin response latencies in the foot (P=0.009 and P=0.033 respectively). In MG patients with dysphagia, this cannot solely be attributed to the parasympathetic system; sympathetic dysfunction was also found to be associated with increased dysphagia severity. It is concluded that the swallowing function should be evaluated in MG with or without dysphagia symptoms, especially in terms of esophageal phase dysfunction.

Hippocampal malrotation (HIMAL) is an anatomical phenomenon appearing as incomplete rotation of the hippocampus in the course of ontogenesis. The relationship between HIMAL and epilepsy is unclear. We analyzed clinical observations of 25 patients (13 female/12 male, mean age 11.38±4.71 years) with HIMAL but without other brain anomalies. Brain MRI data and EEG recordings of 19 patients (76%) were considered. In the examined group, HIMAL was left-sided in 21 (84%), right-sided in 2 (8%), and bilateral in 2 of the patients (8%) as well. In 20 patients (80%), convulsions were manifested. A normal EEG pattern was found in 7 subjects (38%), whereas in 12 patients (62%) the pattern was abnormal. Seizures were observed in all patients with left-sided HIMAL, but only 1 patient demonstrated spike-and-wave activity on the side of malrotation. Our results do not support a strictly direct causative role for HIMAL in the pathogenesis of childhood temporal lobe epilepsy, but this developmental brain abnormality should be considered a significant factor promoting such a pathological condition.

In our study, we investigated the effects of sinapic acid (SA), known for its antioxidant, antimicrobial, anti-inflammatory, and anticancer properties, on penicillin-induced epileptiform activity in rats. Forty-two adult male Wistar rats were divided into groups: sham (Sh), only SA (oSA), control (C), diazepam (Dzm), 10 mg/kg SA (SA10), and 20 mg/kg SA (SA20). Animals were anesthetized, recording electrodes were placed on the left somatomotor cortex area, and a 120-min-long electrocorticogram (ECoG) recording was taken. Rats of four groups (C, Dzm, SA10, and SA20) were subjected to microinjections of penicillin G potassium into the left somatomotor cortex (500 U/2.0 μl); diazepam and SA were administered i.p. 30 min before the penicillin injection. Levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) were determined by the ELISA. The onset time of the first epileptiform activity, spike-wave frequency (DDS), total DDS, and spike-wave amplitude (DDG) of epileptiform activity were analyzed. It was found that the onset time of the first epileptiform activity in the SA10 and SA20 groups was significantly longer than in the C group. Time-dependent DDS and total DSS in the SA10 and SA20 groups were found to be significantly lower than those in the C group. There was no significant difference between the groups in terms of DDG. The levels of SOD, CAT, and GPx in the SA10 and SA20 groups were higher than those in the C and Sham groups, whereas the MDA levels were lower. In conclusion, SA prolongs the onset latency of the first epileptic activity, reduces time-dependent DDS and total DDS, and causes increases in the SOD, CAT, and GPx levels, suggesting that this drug can be used in the treatment of epilepsy, and it may shed light in future studies.