[Galvanic vestibular stimulation in physiological and clinical studies in recent years].

Galvanic vestibular stimulation is a simple, harmless, noninvasive and low-cost research technique. In spite on a long history, it has been recently found popularity as a research tool. At present occurs of its revival as a research and diagnostic tool. Considerable effects of such stimulation for motor, visual, somatosensory, vestibular and cognitive/emotional function as well as for a range of neurological and psychiatric disorders have been reported. Obviously, any process that is able to extract an information due to head acceleration signals is a candidate on galvanic vestibular stimulation. In this review, we describe the basic physiological mechanisms of action of galvanic vestibular stimulation. We also consider a modern data of its influence on human, obtained in physiological and clinical studies.

[New approaches in the study of neuroplasticity process in patients with central nervous system lesion].

Methods which on one hand can ensure the patient's mobility and on other hand activate afferents inputs are the main in rehabilitation treatment. Recent studies has shown that plasticity is structural base of recovery after central nervous system injury. Reorganization of cortical areas and increase of preserved structures functional effectiveness (intensification afferent input) are an anatomical basis of plasticity. However, sensory correction methods, without accounting of functional condition of patients, can lead to the formation of pathological symptoms: spasticity, hyperreflexia, etc. So the main aim is to study adequate management of the neuroplasticity process. This problem cannot be solving without modern methods of neuroimaging and brain mapping. The new approach for study cortical mechanisms of neuroplasticity, responsible for locomotion, was developed in the present study. This approach is complex use of functional magnetic resonance imaging (fMRI) and navigation transcranial magnetic stimulation (nTMS). It was showed that vast fMRI activation area in the first and the second sensorimotor area emerges with passive sensorimotor paradigm using that imitate backing load during walking. The mechanical stimulator footsteps backing zones "Corvit" uses for create this paradigm, nTMS examination, which used after fMRI, help localize the motor representation of muscles which control locomotion more accurately. We guess that new approach can be used for neuroplasticity process study and assessment of neuroplasticity changes during rehabilitation for restore and correct the walking.

[Comparative efficacy of different regimens of locomotor training in long-term space flights by the data of biomechanical and electromyographic parametrs of walking].

Biomechanical and electromyographic characteristics of locomotion were investigated before and after space flight on the 3rd, 7th and 10th day after landing in 18 cosmonauts--crewmembers of long-term ISS space flights. It was shown that microgravity causes the development of significant changes in biomechanical and electromyographic characteristics of walking. Decrease of the angular displacement amplitude in leg joints, reduction of the length of the double step, increase of the electromyographic cost of locomotion were recorded after flight. It was also shown that interval locomotor physical training in long-term space flights in the regimen of alternation running and walking prevents physiological cost of locomotor movements increase after space flight and provides more effective maintenance of the neuromuscular system functions after flight. After flight smaller changes of biomechanical and electromyographic characteristics of walking were observed in cosmonauts who used locomotor training in interval regimen.

[The role of spinal motoneurons in the mechanisms of hypogravitational motor syndrome development].

Studies results of gravity unloading influence on spinal control system of muscle structure and functions are summarized. It was shown that demyelization of axons due to reduction of genes expression responsible for myelin proteins synthesis, decrease in one of the key enzymes of cholinergic system--cholineacetyltransferase activity, alteration of normal kinetics of quantal and non-quantal neurotransmitter secretion, impaired autoregulation of acetylcholine secretion from motor nerve endings through presynaptic cholinergic receptors, slowing of axonal transport of substances in motor neurons that innervate postural muscles played the important role in the development of hypogravitational motor symptoms. At the same time, the evidences of neuroprotective mechanisms enclosing (increase in heat shock proteins Hsp25 and Hsp70 expression), that hinder apoptosis development in motor neurons and glial cells in the spinal cord under conditions of model hypogravity, were revealed.

[Neuronal control of posture and locomotion in decerebrated and spinalized animals].

We have found that the brainstem-spinal cord circuitry of decerebrated cats actively maintain the equilibrium during standing, walking and imposed mechanical perturbations similar to that observed in intact animals. The corrective hindlimb motor responses during standing included redistribution of the extensor activity ipsilateral and contralateral to perturbation. The postural corrections in walking cats were due to considerable modification of EMG pattern in the limbs as well as changing of the swing-stance phases of the step cycle and ground reaction forces depending of perturbation side. Thus the basic mechanisms for balance control of decerebrated animals in these two forms of motor behavior are different. Balance-related adjustments relied entirely on the integration of somatosensory information arising from the moving hindquarters because of the suppression of vestibular, visual, and head-neck-trunk sensory input. We propose that the somatosensory input from the hindquarters in concert with the lumbosacral spinal circuitry can control the dynamics of the hindquarters sufficient to sustain balance. We found that, after isolation from the brainstem or forebrain, lumbosacral circuits receiving tonic epidural electrical stimulation can effectively control equilibrium during standing and stepping. Detailed analyses of the relationships among muscle activity, trunk kinematics, and limb kinetics indicate that spinal motor systems utilize a combination of feedback and feedforward strategies to maintain dynamic equilibrium during walking. The unexpected ability of spinal circuitries to exert efficient postural control in the presence of epidural electrical stimulation in decerebrated and spinal cats have significant implications for the potential of humans with a severe spinal cord injury to regain a significant level of functional standing and walking capacities.

[The effects of support-proprioceptive deprivation on visual-manual tracking and vestibular function].

To determine the effects of support and proprioceptive afferentation on characteristics of the visual-manual tracking (VMT) we used a model of weightlessness - horizontal "dry" immersion. Altogether 30 subjects who stayed in immersion bath from 5 to 7 days were examined to evaluate the accuracy of VMT in tasks to pursue the jerky (saccadically) and smooth (linear, pendular and circular) movement of a point visual stimulus. Examinations were performed before, during and after immersion using electrooculography (to record eye movements) and a joystick (to record hand movements) with a biological visual feedback - one of the two visible stimuli on the screen matched the current angle of the joystick handle. Computerized visual stimulation programs were presented to subject using a virtual reality glasses. We analyzed time, amplitude and velocity characteristics of the visual and manual tracking (VT and MT), including efficiency ratio (eVT and eMT) and gain (gVT and gMT) as ratios of respectively amplitudes and velocities of eyes/hand movements to the stimulus movement. eVT was significantly decreased in comparison with baseline all the time while subject lied in the immersion bath and until R+4 day after immersion, eMT was significantly decreased only on I-1 and I-3 days in immersion. gVT significantly differed from baseline only on I-3 and I-6 days in immersion and R + 1 day after immersion. We found no significant changes in gMT. Evaluations of the vestibular function (VF) were performed before and after immersion using videooculography approach. We analyzed statical torsional otolith-cervical-ocular reflex (OCOR), dynamical vestibular-cervical-ocular reactions (VCOR), spontaneous eye movements (SpEM), the accuracy of perception of subjective visual vertical (SVV). After immersion 47% of subjects had significant decrease of OCOR with a simultaneous significant increase of VCOR on 37% of subjects as well as significant changes in accuracy of perception of SVV which correlated with changes in OCOR. We found correlation between characteristics of the VT and MT, between characteristics of the VF and VT and found no correlation between VF and MT. It was found that removal of the support and minimization of the proprioceptive afferentation has a greater impact upon accuracy of the VT then accuracy of the MT.

[Mechanical stimulation of soles' support zones: non-invasive method of activation of generators of stepping movements in man].

The effects of mechanical stimulation of the soles' support zones in regimens of slow and fastwalking (75 and 120 steps per minute) were studied using the model of supportlessness (legs suspension). 20 healthy subjects participated in the study. EMG activity of hip and shin muscles was recorded. Kinematic of leg movements was assessed with the use of videoanalysis system. Support stimulation was followed by leg movements in 80% of cases, in 53% it was a locomotion-like movement. EMG bursts accompanied the movements. Involvement order and alteration of bursts in muscles were similar to voluntary walking. EMG activity occurred with a delay of 5.17 ± 1.08 seconds for hip muscles and 14.01 ± 2.82 seconds for shin muscles, frequency of bursts differed from stimulation frequency. Support stimulation was followed by leg movements in 80% of cases, in 53% of which they had characteristics of locomotions being accompanied by the burst-like electromyographic activities. Involvement order of the leg muscles and organization of antagonistic muscles activities were analogous to that of voluntary walking. The latencies of electromyographic activity in hip muscles composed 5.17 ± 1.083 s and 14.01 ± 2.82 s - for shin muscles, frequency of bursts differed significantly from stimulation frequency. In 31% of cases the electromyographical activity following the stimulation of the soles' support zones was not burst-like. Its amplitude rose smoothly reaching a certain level that was subsequently maintained. Results of the study showed that soles' support zones stimulation in regimen of locomotion can activate a locomotor generator and that effect evoked by this stimulation includes not only rhythmical but also non-rhythmical (probably postural) components of walking.

[Specifics of activation of cortex by stimulation of support receptors in healthy subjects and in patients with lesions of CNS].

Results of basic studies in space medicine revealed the mechanism of motor disorders and the importance of support input in regulation of the tone and posture system of the mammals. Progress in functional magnetic resonance tomography (fMRT) enabled in vivo estimation of activity of various parts of the brain during stimulation of support afferent pathways. The goal of our study was to detect specific activation of the cortex during stimulation of support input in healthy subjects and in patients with lesions of CNS. The study included 19 healthy volunteers (mean age of 38 ± 15, 13 years) and 23 patients with cortical-subcortical ischemic stroke (mean age 53 ± 9.07); all subjects underwent fMRT. During scanning of each subject, support areas of the foot soles were stimulated to imitate slow walking using the block design. In healthy volunteers, primary somatosensory cortex, premotor and dorsolateral cortex, and insula were significantly activated (corrected <0.05 at cluster level). In patients with stroke, pattern of activation of the supraspinal systems of locomotion control clearly depended on the stage of the disease. In patients with cortical-subcortical stroke undergoing motility rehabilitation, the sensomotor locomotion module was predominantly activated as the contralateral pattern.

[Myelination disorders in mechanism of hypogravity motor syndrome development].

When modeling effects of hypogravitation by the method of hindlimb unloading in rats the area of cross-section in lumbar part of a spinal cord was found to reduce. The analysis of spinal cord slides showed that these changes are associated with a decrease in the area of white substance of a spinal cord. Data obtained are consistent with our previous observation of a decrease in expression of the genes encoding myelin proteins. Results of our researches give the good reasons to believe that miyelinization failure in CNS is one of the factors that underlie the development of hypogravitational motor syndrome.

[Transcutaneous electrical stimulation of the spinal cord: non-invasive tool for activation of locomotor circuitry in human].

A new tool for locomotor circuitry activation in the non-injured human by transcutaneous electrical spinal cord stimulation (tSCS) has been described. We show that continuous tSCS over T11-T12 vertebrae at 5-40 Hz induced involuntary locomotor-like stepping movements in subjects with their legs in a gravity-independent position. The increase of frequency of tSCS from 5 to 30 Hz augmented the amplitude of evoked stepping movements. The duration of cycle period did not depend on frequency of tSCS. During tSCS the hip, knee and ankle joints were involved in the stepping performance. It has been suggested that tSCS activates the locomotor circuitry through the dorsal roots. It appears that tSCS can be used as a non-invasive method in rehabilitation of spinal pathology.

[Activation of the sensorimotor cortex with the use of a device for the mechanical stimulation of the plantar support zones].

Studies of the control movements mechanisms have been performed in the interest of space medicine were the basis for the development of the concept about the leading role of the support afferent input in the regulation of postural-tonic system of mammals. Introduction of functional magnetic resonance imaging (fMRI) made it possible to investigate in-vivo brain mapping during stimulation of support afferent input. The aim of our study was to investigate brain activation due to mechanical support stimulation of the soles with the special device "Korvit". 12 healthy participants (6 women, 6 men; average age = 28.8 years) were scanned. fMRI protocol for each person consisted of 2 different blocked paradigms: soles stimulation in stance imitation (1) and slow walking imitation (2) modes. The results were analyzed with statistical program SPM5 for each person and then for the whole group. In all our paradigms there was significant (P(correct) < 0.05 for cluster level) activation of primary somatosensory, premotor and dorsolateral cortex, insula. During the stance imitation mode, extensive prefrontal cortex activation was observed; during the slow walking imitation mode there was activation of different primary and secondary sensorimotor cortex areas.

[Serotoninergic system morphofunctional aspects in control of postural and locomotion function].

Different mediator systems including serotoninergic one can influence animal's locomotor behavior. It has been shown that the spinal cord in the absence of supraspinal control is able to induce the locomotor activity in hindlimbs and afferent system can activate this mechanism. In behavioral studies on the rats with complete transection of the spinal cord it has been demonstrated that the pharmacological blocking of serotoninergic system results in depression of motor activity mediated by activation of support reactions. Histological studies did not reveal any effects of activation of support reactions on the safety of neurons as well as on the distribution of synaptic contacts within L2-L4 spinal segments. At the same time it has been shown that blockade of the serotoninergic system results in alterations of cells located in 1-3 laminae of dorsal horns, and in 7 Rexed's lamina as well as in redistribution of synaptic contacts in 1-4 Rexed laminae of the spinal cord dorsal horns.

[Characteristics of postural corrective responses before and after long-term spaceflight].

Balance function is dramatically deteriorated after exposure to microgravity. The purpose of the present study was to investigate the role and the contribution of different gravity sensory systems to the development of balance impairment after long-term spaceflights. Postural perturbations (pushes to the chest) of the threshold, medium, and sub-maximal intensities were produced in eight cosmonauts before, and on the day 3, 7, and 11 following spaceflight. Postural corrective responses were analyzed by anterior-posterior body sway fluctuation and electromyographic activity of leg muscles. The characteristics of the postural corrective responses changed significantly on the day 3 following spaceflight: the amplitude of posterior sway caused by perturbation of threshold intensity was increased reaching 135% ofpreflight value; the corrective responses lasted more than 6 s in 50% of all trials, while it did not last more than 4 s in 96% before spaceflight. The EMG responses were characterized by increased contribution of medium- and long-latency reactions. On the day 11 following spaceflight, most of the characteristics of postural corrective responses were close to preflight values. We assumed that the balance alterations after spaceflight are caused by changes in weightlessness of functions of two main gravity sensory systems, namely, weight-bearing and vestibular one. The deficit of weight-bearing afferentation triggers a decline of the extensors' muscle tone, while changes of vestibular function cause a decline of accuracy of postural corrections.

[About possible specialization of different compartments of a motoneuron axon for synthesis of specific proteins].

The spontaneous quantum secretion of neurotransmitter and its regulation through the system of presynaptic acetylcholine receptors have been studied on a neuromuscular preparation of rat m. soleus of intact animals and animals in which the axonal transport was blocked via the application of colchicine to the sciatic nerve. It was shown that, after six days of colchicine application, the spontaneous quantum secretion, the reaction of presynaptic membrane, and the reaction of neurosecretory apparatus to the depolarization of nerve endings via increase of the content of potassium ions in the environment and to the activation of presynaptic receptors by carbachol are not disturbed. Keeping in mind a rather short half-life of proteins that take part in the exocytosis and its regulation, it may be concluded that their functioning does not depend on the state of the axonal transport. These data correspond to the hypothesis put forward earlier that the synthesis of some proteins performing their function in nerve terminals occurs directly at the site of their utilization but not in the perikaryon, as it has been traditionally assumed.

[Some approaches to the countermeasure system for a mars exploration mission].

In article discussed physiological and methodical principles of the organization of training process and his (its) computerization during Martian flight in conditions of autonomous activity of the crew, providing interaction with onboard medical means, self-maintained by crew of the their health, performance of preventive measures, diagnostic studies and, in case of necessity, carrying out of treatment. In super long autonomous flights essentially become complicated the control of ground experts over of crew members conditions, that testifies to necessity of a computerization of control process by a state of health of crew, including carrying out of preventive actions. The situation becomes complicated impossibility of reception and transfer aboard the necessary information in real time and emergency returning of crew to the Earth. In these conditions realization of problems of physical preventive maintenance should be solved by means of the onboard automated expert system, providing management by trainings of each crew members, directed on optimization of their psychophysical condition.

[Effects of long-term space flights on organization of horizontal gaze fixation reaction].

Results of Russian-Austrian space experiment "Monimir" which was a part of international space program "Austromir" are presented in this paper. Characteristics of horizontal gaze fixation reaction (hGFR) to visual targets were analyzed. Seven crewmembers of "Mir" space station expeditions took part in the experiment. Experiments were carried out 4 times before space flight, 5 times in flight and 3-4 times after landing. There were revealed significant alterations in characteristics of gaze fixation reaction during flight and after its accomplishing, namely: an increase of the time of gaze fixation to the target, changes of eye and head movements' velocity and increase of the gain of vestibular-ocular reflex, that pointed out to the disturbances of the control mechanisms of vestibular-ocular reflex in weightlessness caused by changes of vestibular input's activity. There was discovered also the difference in the strategies of adaptation to microgravity conditions among the cosmonauts of flight and non-flight occupation: in the first group exposure to weightlessness was accompanied by gaze hypermetry and inhibition of head movements; in the second one--on the contrary--by increase of head movement velocity and decrease of saccades' velocity.

[Quantitative evaluation of the effectiveness of physical contermeasures against motor disorders in long-duration space flight].

Regression analysis has been applied to determine the dependence of the motor system status (MSS) in long-duration space flight on the physical training programme (PTP), and flight duration (FD). Analyzed were graphical data presented in previous papers. Statistical analysis brought to light a high level of MSS-PTP relationship described as a 5-degree polynomial and a less explicit, yet statistically reliable MSS-FD relationship which is most adequately approximated by a 6-degree polynomial.

[Medical care for Russian cosmonauts' health on the ISS].

Established with the personal participation of O.G. Gazenko, the Russian system of medical care for cosmonauts' health has been largely preserved till this day. The system was fully functional on board the orbital complex MIR and, with appropriate modifications, has been adopted as a core of the medical care for Russian members of the ISS crews. In the period of 2000-2008, 22 cosmonauts were members of 17 ISS increments from 140 to 216 days in duration. The main functions of the medical care system were to control health, physical and mental performance, and to support implementation of space researches. The flow of readaptation to the normal gravity was, in most cases similar to what has been typical on return from the Russian orbital stations; some deviations are accounted for by application of the in-flight countermeasures. The paper familiarizes reader with some aspects of the theoretical work of academician O.G. Gazenko in the field of medical care in space flight. It outlines the principles of ISS medical management. The integrated medical support system combines medical equipment and items available on the Russian and US segments; the integrated medical group consists of flight surgeons, medical experts and biomedical engineers of the international partners and coordinates planning and implementation of medical operations. Also, challenges of health care on the phase of ISS utilization are defined.