Open Access
Access granted
Subscription Access
Vol 43, No 5 (2017)
- Year: 2017
- Articles: 14
- URL: https://journals.rcsi.science/0362-1197/issue/view/10934
Article
Glorious jubilee of a renowned scientist
491-491
Spinal and sensory neuromodulation of spinal neuronal networks in humans
Abstract
The present experiments were designed to gain additionally insight into how the spinal networks process direct spinal stimulation and peripheral sensory inputs to control posture and locomotor movements. We have developed a plantar pressure stimulation system that can deliver naturalistic postural and gait-related patterns of pressure to the soles of the feet to simulate standing and walking, thereby activating and/or modulating the automated spinal circuitry responsible for standing and locomotion. In the present study we compare the patterns of activation among selected motor pools and the kinematic consequences of these activation patterns in response to patterned heel-to-toe mechanical stimulation of the soles of the feet, and/or transcutaneous electrical spinal stimulation, for postural and locomotion regulation. The studies were performed in healthy individuals (n = 12) as well as in subjects (n = 2) with motor complete spinal cord injury. We found that plantar pressure stimulation and/or spinal stimulation can effectively facilitate locomotor output in the subjects placed with their legs in gravity neutral position. We have shown synergistic effects of combining sensory and spinal cord stimulation, suggesting that the two networks are different, but complementary. Also we provide evidence that plantar stimulation could serve as a novel neuro-rehabilitation tool alone or as part of a multi-modal approach to restoring motor function after complete paralysis due to SCI.
492-500
Electrophysiological brain activity during the control of a motor imagery-based brain–computer interface
Abstract
This article considers the features of five electroencephalogram patterns that are most frequently extracted by the independent component analysis when subjects imagine the movement of their hands during the control of a brain–computer interface (BCI). The solution of the EEG inverse problem using the individual geometrical head model shows that the sources of the revealed patterns are located at the bottom of the left and right central sulci, as well as in the left premotor cortex, supplementary motor area, and precuneus. The functional value of the patterns is discussed by comparing the location results with the results of the metaanalysis of the published data that were obtained using a functional magnetic resonance imaging. The source locations are the same for seven healthy subjects and four poststroke patients with subcortical damage location. However, despite the same locations, the two groups of subjects significantly differed in the frequency characteristics of the revealed patterns; in particular, the patients had no clearly pronounced activity in the upper α-band and were characterized by a much lower level of inhibition of rates in the primary somatosensory areas during motor imagery.
501-511
Effects of transcutaneous electrical spinal cord stimulation on stepping patterns during walking
Abstract
Effects of transcutaneous electrical spinal cord stimulation (tESCS) on the parameters of stepping movements in healthy subjects were investigated during two kinds of activity: walking on a moving treadmill belt (active treadmill) as well as pushing the treadmill belt by effort of the legs (passive treadmill). It was found that the total interference electromyogram (EMG) activity during stepping performance on a passive treadmill was 1.5–2 times higher than during stepping on an active treadmill. In addition, the amplitude of angular displacement of the hip joint and ankle was 2.5 times and 1.7 times higher, respectively, during passive vs. active treadmill, while the duration of stepping cycle decreased by 19%. Although the muscles were exposed to different load and the parameters of motion on the active and passive treadmill were different, tESCS caused an increase in the total EMG activity in 96% of cases both on the active and on the passive treadmill. In both cases, the stepping cycle period decreased by 4–43% in all subjects. These results suggest that tESCS can affect voluntary stepping patterns under conditions of different afferent control.
512-517
Effect of transcutaneous electrical spinal cord stimulation on the blood flow in the skin of lower limbs
Abstract
Changes in the blood flow in the skin of the plantar surface of the hallux were investigated by laser Doppler flowmetry in eight healthy subjects during transcutaneous electrical spinal cord stimulation (tESCS) with the pulse parameters used to activate locomotion. Continuous tESCS in the area of C5–C6 vertebrae did not cause significant changes in the blood flow, while electrical stimulation at T12–T1 and L1–L2 levels resulted in an increase in skin perfusion by 22–27%. Wavelet analysis of microcirculatory fluctuations showed that tESCS induced flaxomotions in the range of sensory peptidergic fibers and enhanced the amplitude of fluctuations of microcirculation in the endothelium-dependent range. These results suggest that tESCS stimulates microcirculation in the skin mainly due to antidromic stimulation of sensory peptidergic nerve fibers, which promotes activity of microvascular endothelium, vasodilator secretion, a decrease in vascular resistance, and an increase in microcirculation.
518-523
Response of external inspiration to the movements induced by transcutaneous spinal cord stimulation
Abstract
The dynamic of the parameters of lung ventilation and gas exchange have been studied in 10 young male subjects during involuntary stepping movements induced by transcutaneous spinal cord electrical stimulation applied in the projection of T11–T12 vertebrae and during voluntary stepping movements. It has been found that the transcutaneous spinal cord stimulation inducing stepping movements leads to an increase in breathing frequency and a reduction in tidal volume. These effects may be mediated by some neurogenic factors associated with muscular activity during stepping movements, the activation of abdominal expiratory muscles, and the interaction between the stepping pattern and breathing generators.
524-531
Rehabilitation potential of post-stroke patients training for kinesthetic movement imagination: Motor and cognitive aspects
Abstract
The rehabilitation potential of post-stroke patients was evaluated after a rehabilitation procedure using a hand exoskeleton controlled via a brain–computer interface (BCI). Examples are given for parameters describing the motor and cognitive functions and the capacity for kinesthetic movement imagination. It is emphasized that instrumental quantitative methods are important to use for adequate assessment of both the rehabilitation potential and the effectiveness of the BCI + exoskeleton procedure.
532-541
Ground reaction force values in cosmonauts during locomotor exercises on board the International Space Station
Abstract
Optimal methods for the prevention of negative impact of weightlessness have been developed based on the concept of Kozlovskaya, which states that support afferentation plays a trigger role in the development of the hypogravity motor syndrome. In this study, the maximal vertical ground reaction force (GRF) values were analyzed when locomotor training was performed on a BD-2 treadmill in long-term spaceflights. The study involved 12 cosmonauts. Recorded segments of the locomotor training (4554) performed in active (motor-driven) and passive (non-motor-driven) modes of BD-2 belt motion were analyzed. The data were analyzed by the methods of correlation and regression analysis and the nonparametric Mann–Whitney test. It was found that when running, regardless of the treadmill modes, an increase in the axial load by 1 kg was associated with a more than 1-kg increase in GRF; during walking an increase in GRF was less than 1 kg. As the speed increased, the GRF values increased most quickly when running in a passive mode and most slowly when walking in a passive mode. The GRF values in different BD-2 modes depended on both individual parameters of cosmonauts and locomotion types (walking or running). Our data can be the basis for the individualization of locomotor training onboard the ISS.
542-548
Effects of bed rest and the use of intermittent centrifugation to protect human balance and neuromotor reflexes
Abstract
This AG prescription had little functionally relevant effect on balance control, but may have had some salutary effect on neuromotor reflexes.
549-556
Vestibular function and space motion sickness
Abstract
The vestibular system plays an important role in intersensory interactions and gravitation is a natural stimulus for its receptors. Weightlessness alters the input signals of the otoliths and their effect on the pattern and dynamics of changes in the vestibular function (VF), which is accompanied by development of space adaptation syndrome (SAS) and space motion sickness (SMS). These changes occur both during the spaceflight (SF) and after returning to Earth, but the mechanisms of their development are still poorly understood and require special studies. In total, 47 Russian cosmonauts (crewmembers of long-term International Space Station (ISS) missions) have participated in the studies into VF before and after SF and nine of them, in onboard studies during SF (129–215 days) as a part of the Virtual space experiment (stage 1). Electro- and video-oculography are used to record spontaneous eye movements (SpEM), static vestibular–ocular responses during head tilts to the right or left shoulder (static otolith–cervical–ocular reflex, OCOR), and dynamic vestibular-ocular response during the head rotation around the longitudinal axis of the body. The examination is accompanied by personal and questionnaire survey on subjective responses and complaints of cosmonauts about SAS and SMS. Significant changes in SpEM (drifts of eyes, spontaneous and gaze-evoked nystagmus, and arbitrary saccades) and a decrease in OCOR (statistically significant decrease in the amplitude of ocular counter-rolling in response to head tilts up to its absence or inversion, an atypical OCOR) are observed during SF. An atypical OCOR is observed at the beginning of adaptation to weightlessness in seven of the nine cosmonauts (the first one to two weeks of SF) and repeatedly throughout the flight in all cosmonauts regardless of whether it is their first flight or not. Atypical vestibular responses after SF, similar to the responses during SF, are observed in several cosmonauts by day 9 after flight. It has been shown that atypical OCOR variants are more frequently observed in the subjects lacking any previous space experience, as well as a more pronounced decrease in this response with a concurrent increase in the response of the semicircular canals. It is also demonstrated that repeated SFs lead to a considerable shortening in the after-flight readaptation to terrestrial conditions and a considerable decrease in the degree of vestibular disorders. In the initial period of SF, the changes in VF are correlated with the complaints and manifestations of SAS and SMS; however, the complaints and the corresponding symptoms are unobservable during the further flight despite significant changes in the VF state. The patterns of the VF disorders associated with the impact of weightlessness and observed during and after SF are very similar, allowing these disorders to be regarded as SAS and SMS of different severities (intensities).
557-568
Metabolic features of cosmonauts after ballistic descent from the Earth orbit
Abstract
The features of metabolic reactions in five cosmonauts after long-term flights on the International Space Station (ISS) and landing along a ballistic trajectory and in the cosmonauts returning to Earth in the mode of automatic controlled descent were studied. Venous blood samples were collected, and 50 biochemical parameter values that reflect the functional state of organs and tissues and characterize the main metabolic pathways were determined. On the first day of the recovery period after ballistic descent, the activity of the myocardial, liver, and gastrointestinal enzymes in the blood serum of cosmonauts was increased 1.3- to 2.1-fold; a number of the parameter values exceeded the upper normal limit. The level of C-reactive protein increased fivefold as compared with the preflight values. Marked signs of glycolysis, glycogenolysis and lipolysis activation as well as disorders of acid–base balance were observed. Changes in the biochemical parameter values in cosmonauts after landing along a ballistic trajectory differed significantly from those revealed in the same cosmonauts after long-term missions followed by automatic controlled descent to Earth. Negative metabolic changes tendency after landing along a ballistic trajectory remained for at least 14 days of the recovery period. It was concluded that changes in the metabolic reactions of cosmonauts after long-term missions to the ISS depend on the flights final stage conditions. After landing on Soyuz spaceships in the ballistic descent mode, the cosmonauts had adverse prognosis changes in the biochemical values characterizing the state of the cardiovascular system and marked shifts in the activity of the liver and gastrointestinal constellation enzymes. The dynamics of carbohydrate, lipid, and protein metabolism as well as acid–base balance indicates a significant tension of all body systems and exhaustion of its functional reserves.
569-577
Reviews
Gravity mechanisms in tonic motor system. Neurophysiological and muscle aspects
Abstract
Nowadays it is widely believed that the animal motor system historically evolved under the powerful pressure of gravity forces. By the late 1970s, many manifestations of the microgravity effects on the motor system had already been known. At the same time, the basic sensorimotor relationships during exposure to zero-gravity remained unexplored. The article considers the main results of the studies of the scientific school of I.B. Kozlovskaya regarding the roles of the gravitational forces in the functioning of the tonic motor system in humans and other mammals. In these studies, it was demonstrated that the muscle tonic system is relatively independent and possesses its own structures and mechanisms at every level—from receptors to effectors. The support afferent input plays the main role in the regulation of the postural tonic system. The withdrawal of the support afferentation leads to the decline of the tonic motor units activity in extensor muscles and the alteration of the motor units recruitment patterns in the spinal cord. The decline of the tonic activity of the extensor motoneurons triggers on the development of the sensorimotor effects of microgravity including atony and muscle atrophy.
578-590
New approaches in the rehabilitation of patients with central nervous system lesions based on the gravitational mechanisms
Abstract
This review discusses the functioning of the motor system under normal and reduced gravity. Analysis of the experimental data led to the conclusion that all changes in the functioning of tonic muscular system are related to each other. When transiting to the state of microgravity, changes are caused by one common factor, namely a sharp decrease in the activity of support afferent input, specifically oriented to the perception and analysis of gravitational loads and firmly embedded in the mechanisms of postural synergism organization. We analyzed data obtained in studies on the activation of cortical areas of the brain during the stimulation of support afferents in order to test the hypothesis that such stimulation in both healthy subjects and patients with neurologic deficiency leads to activation of both the sensory and motor cortex involved in supraspinal control of the movement of the lower limbs, in particular when walking.
591-600
Influence of long-term intracortical microstimulation on the motor cortex
Abstract
Long-term (0.5–1 s) stimulation of the hand region of the motor cortex in both macaque and human through a microelectrode by a series of biphasic current pulses of small amplitude evokes different complex, coordinated movements of the hand. There are two different opinions on how these movements are produced. The first hypothesis associates the movements with the presence of specific subregions in the motor cortex, which reflect different ethologically relevant categories of movement. According to the second hypothesis, these evoked complex movements are the artifacts of electrical stimulation. This article discusses the results of a number of studies in favor of each of the hypotheses. The conclusion about the validity of the first hypothesis is based on the analysis of the results of microstimulation and their comparison with the data obtained by the latest methods without the use of electric current. Moreover, this finding suggests the possibility of testing the condition changes of the monkey motor cortex through analysis the characteristics of the movements caused by long-term microstimulation.
601-605