The question of the activity of muscles that provide the realization of imaginary movement is essential in the rehabilitation of motor disorders using neurointerfaces. The literature data on this issue are contradictory. The paper analyzes the EMG activity of the shin and thigh muscles of 40 healthy volunteers when working with a neurointerface based on kinesthetic motor imagery of walking in place and supplemented with the << Biokin >> robotic limb movement device (mechanotherapy), activated in case of successful motor imagery. It is shown that working with a neurointerface, on average for subjects, leads to an increase in muscle activity when motor imagery of walking compared to rest, and activation of the mechanical training device (AM) further increases muscle activity, with its effect being more pronounced in the muscles of the leg from which motor imagery of walking begins. The nature of muscle reactions to the task of motor imagery of walking is individual. AM when working with a neurointerface, the number of subjects with pronounced EMG activity increases, as does the number of significant correlations between the activity of the muscles of the lower limbs. Thus, the use of neurointerfaces based on motor imagery of walking and the addition of AM as feedback allows activating the muscles of the lower extremities, which is important in clinical practice in the rehabilitation of movements.

Multisegmental transcutaneous electrical stimulation of the spinal cord (sсTS), affecting spinal neural networks and motor pools of leg muscles, was used to correct treadmill walking in stroke patients. The study involved 15 patients in the recovery period after acute cerebrovascular accidents. A noninvasive spinal neuroprosthesis with a multichannel stimulator and a system for detecting phases of the walking cycle (“Cosima”, Russia) was used to activate motor pools of leg flexor muscles in the transfer phase, activation of motor pools of extensor muscles in the stance phase in combination with continuous activation of spinal locomotor networks. Using of sсTS during walking on a treadmill increased the amplitude of movements in the ankle joint and the stride length on the paresis side, as well as a decreased the asymmetry of both legs in the phases of the gait cycle. The clearance of the paretic leg lift increased in 80 of patients. With a combination of continuous and phase-dependent stimulation, the increase in the range of motion in the joints was maximal compared to phase-dependent or only constant stimulation. The obtained data demonstrate that the proposed algorithm of the sсTS modulates the parameters of walking movements in patients with the consequences of cerebral circulation accidents and can be considered as a promising method of motor rehabilitation.

An Erratum to this paper has been published: https://doi.org/10.1134/S0362119723970029

Исследовалось влияние чрескожной электрической стимуляции спинного мозга на кинематические параметры движений ипсилатеральной и контралатеральной ноги у здоровых испытуемых при ходьбе по беговой дорожке (1.5-1.7 км/ч). Стимулирующие электроды располагались на 2.5 см латеральнее средней линии спинного мозга с правой и левой стороны на уровне L1 и T11 позвонков. Во время фазы опоры применяли стимуляцию на уровне L1 с частотой 15 Гц, затем во время фазы переноса - на уровне T11 с частотой 30 Гц, далее следовала чередующаяся стимуляция L1 и T11. Влияние стимуляции в фазе переноса (T11) было более эффективным, чем в фазе опоры (L1), а наибольшее изменение кинематических параметров наблюдалось при сочетании стимуляции L1 и T11. При ритмической стимуляции с одной стороны в шаге ипсилатеральной ноги увеличивалась амплитуда изменения углов в тазобедренном, коленном и/или голеностопном суставах, длина переноса и высота подъема ноги. В шаге контралатеральной ноги наблюдались схожие, но менее выраженные изменения параметров. Увеличение продолжительности стимуляции в фазе переноса на 10% вызывало изменения кинематических параметров шага ипси- и контралатеральной ноги. Максимальный эффект наблюдался при двусторонней чередующейся стимуляции. Полученные данные показывают, что применение фазозависимой чрескожной электрической стимуляции спинного мозга с учетом естественной синергии может быть инструментом управления кинематическими параметрами движения.

The effect of noninvasive trasnscutaneous spinal cord stimulation (scTS) on walking parameters in patients after a cerebral infarction or ischemic stroke was investigated. It has been shown that after the use of scTS while walking on the floor the speed of movement, the length of the step cycle, the height of the foot elevation and the amplitude of movements in the hip, knee and ankle joints increased, which shows the ability of using scT to correct walking after a stroke. Key words: spinal cord, electrical stimulation, stroke, walking.

The effect of transcutaneous electrical spinal cord stimulation on the kinematic parameters of movement of the ipsilateral and contralateral legs in healthy subjects during treadmill walking at speeds of 1.5 to 1.7 km/h has been studied. The stimulation electrodes were placed 2.5 cm lateral from the right and left sides of the spinal midline at L1 and T11 levels. During the stance phase, stimulation was administered at L1 level at a frequency of 15 Hz; during the swing phase the stimuli was delivered to T11 at a frequency of 30 Hz, followed by alternating stimulation at L1 and T11. The stimulation during the swing phase (T11) was more effective than that during the stance phase (L1); the most impressive changes in kinematic parameters were observed when combined delivery of stimulations to L1 and T11 was performed. With unilateral spinal stimulation, the amplitude of the angles in the hip, knee and/or ankle joints, the length of the transfer, and the height of the leg elevation increased in the ipsilateral leg. Similar but less pronounced changes were observed in the contralateral leg. A 10% increase in the duration of stimulation in the swing phase caused a change in the kinematic stepping parameters both in ipsilateral and contralateral legs. The maximum effect was observed when bilateral alternating stimulation was used. These data show that phasic transcutaneous electrical spinal cord stimulation, using a wide range of natural walking speeds, can be applied to control kinematic movement parameters.

Transcutaneous electrical spinal cord stimulation (SсТS) wascarried out in different phases of the stepping cycle in order tocontrol the kinematic parameters of the step in healthy subjects walkingon a treadmill. ScTS during the swing phase at the T11–T12 levelactivated the flexor motor pools and caused a change in the motionamplitude in the hip, knee and ankle joints, as well as increasedthe height of leg elevation. ScTS at the stance phase at the L1–L2level, addressed to the extensor motor pools, did not affect thekinematics of stepping movements. A shift in the start of T11–T12stimulation to 100–150 ms before the initiation of the swing phaseor its prolongation by 100 ms after the end of the swing phase causedsignificant changes in the kinematics of stepping movements. Essentialfor the start of stimulation is the moment of pushing the leg offthe support a little earlier than beginning of the swing phase .Prolongation of the stimulation period in the swing phase allowsto increase ankle join flexion The choice of the optimal algorithmof phase-dependent ScTS for the activation of flexor and extensormotor pools during the stepping cycle increases the efficiency ofstimulation in motor function rehabilitation techniques.

A novel approach was designed to regulate the stepping movements in human by means of noninvasive electrical transcutaneous spinal cord stimulation (TSCS) to activate the flexor/extensor motor pools of the lower limbs in the gait cycle. Selective stimulation was delivered automatically based on signals from gyroscope sensors, which served to detect the stance and swing phases. The initiation of hip extension was a trigger for stimulating extensor pools (L1) during the stance phase, and the initiation of hip flexion was a trigger for stimulating flexor motor pools (T11) during the swing phase. In healthy subjects ( n = 6) walking on a treadmill, stimulation at L1 with a frequency of 15 Hz decreased the duration of stance phase by 4% ( p = 0.0457), increased the amplitude of movements in the hip joint by 11% ( p = 0.0266), decreased the movement amplitude in the ankle joint by 17% ( p = 0.0081), and increased EMG activities of the extensors vastus lateralis (VL) (by 31%, p = 0.0441) and gastrocnemius medialis (GM) (by 17%, p = 0.0465) and flexors biceps femoris (BF) (by 26%, p = 0.4637) and tibialis anterior (TA) (by 21%, p = 0.0215) relative to walking without stimulation. Stimulation at Т11 with a frequency of 30 Hz reduced the stance phase duration by 3% ( p = 0.0318) and increased the amplitude of movements in the hip joint by 12% ( p = 0.0467), the knee lifting by 25% ( p = 0.0001), and the terminal anthropometric point height above the surface of support by 19% ( p = 0.0001). The changes were accompanied by increases in muscle activities of the flexors BF (by 18%, p = 0.230) and TA (by 14%, p = 0.0170). The reciprocity coefficient decreased in thigh muscles by 15% ( p = 0.0301) and increased in shin muscles by 5% ( p = 0.0452). Alternating spatiotemporal stimulation at L1 and T11 did not significantly change the durations of the gait cycle and its phases, but changed the kinematic characteristics of movements. The amplitude of movements in the hip joint increased in the stance phase. In the swing phase, higher values were observed for the amplitude of movements in the hip joint, the knee lifting, and the terminal anthropometric point height above the surface of support. EMG activities of thigh and shin muscles increased during stimulation at L1 + T11. EMG activity of extensors was higher than that of flexors in the stance phase, while flexor EMG activity exceeded extensor activity in the swing phase. Thus, the data obtained show the possibility of TSCS selectively to activate the motor pools of the lower extremities, and control their activity to regulate the phases of the stepping cycle during human locomotion.

Transcutaneous electrical stimulation of the spinal cord (ScTS) was carried out in different phases of the stepping cycle in order to control the kinematic parameters of the step in healthy subjects walking on a treadmill. ScTS at the T11-T12 level during swing phase activated the flexor motor pools and caused change of the motion amplitude in hip, knee, and ankle joints as well as increased the height of the leg elevation. Stimulation at the L1-L2 level at the stance phase, addressed to the extensor motor pools, did not affect the kinematics of stepping movements. Shift in the beginning of T11-T12 stimulation to 100-150 ms before the initiation of the swing phase or its prolongation by 100 ms after the end of it caused significant changes in the kinematics of the movements. Essential for the start of stimulation is the moment of pushing the foot off the support a little earlier the transfer phase. Prolongation the stimulation period in transfer phase allows to increase ankle joint flexion. The choice of the optimal algorithm of the phase-dependent ScTS for activation of the flexor and extensor motor pools during the stepping cycle increases the efficiency of stimulation in motor functions rehabilitation techniques.

The effects of activation of spinal locomotor centers at the cervical and lumbar levels on interlimb synergies were studied in humans. Subjects were placed on a biomechanical trainer in the supine position and carried out voluntary rhythmic leg movements, moving the carriage of the walking device of the trainer, or performing voluntary arm movements moving the levers of the trainer, or making simultaneous leg and arm movements. In the resting state, sequential transcutaneous stimulation of the spinal cord at three levels (cathode positioned between vertebrae C4/C5, T12/L1, or L1/L2) did not induce leg movements in most subjects, though performance of arm movements in combination with stimulation initiated low-amplitude (less than 10°) movements in all the leg joints. Stimulation of the spinal cord and simultaneous arm movements induced facilitation of the performance of voluntary leg movements, which was apparent as an increase in the integral characteristic of muscle electrical activity and an increase in movement amplitude at the hip joint. The results obtained here may be useful for developing a neurorehabilitation method for patients with impaired motor function.

The recovery of motor functions in chronic spinal rats with locomotor training on a treadmill combined with electrical stimulation of the spinal cord was studied. Training to a bipedal gait on a moving band with the body weight supported and use of either subcutaneous or epidural electrical stimulation (40 Hz) was performed for five days per week for 20–30 min. The dynamics of changes in locomotor capacity using subcutaneous and epidural electrical stimulation and their actions on the neural structures of the spinal cord could be similar. After three weeks of motor rehabilitation, a single stimulation at a frequency of 1 Hz evoked reflex monosynaptic potentials in the hindlimb muscles, while simultaneous rhythmic stimulation of two loci in the spinal cord at a frequency of 40 Hz initiated locomotor-like activity on the moving band of the treadmill. A more marked rhythm was seen after nine weeks of training, which coincided with the appearance of polysynaptic spinal reflexes. Administration of the serotonin receptor agonist quipazine enhanced polysynaptic activity in reflex responses and improved locomotion. Use of noninvasive subcutaneous stimulation in combination with locomotor training was found to be an effective method of activating neural locomotor networks to an extent comparable to that obtained with invasive epidural stimulation.

The effects of transcutaneous electrical stimulation of the spinal cord on the kinematic and electromyographic characteristics of motor responses in the arms and legs muscles in healthy subjects have been studied. The subjects placed in the biomechanical simulator in a supine position and performed voluntary rhythmic leg movements displacing the carriage of the simulator's walking device, voluntary arm movements, moving the simulator levers or performed simultaneous arm and leg movements. During the rest, the sequential stimulation at the level of Th12-L1, L1-L2 and C5-C6 vertebrae did not elicit leg movements in most subjects, however, the arm movements in combination with stimulation of the spinal cord initiated fluctuations in the joints of the legs (amplitude up to 10 angle degrees). The stimulation in combination with arm movements facilitated voluntary leg movements and increased the integral characteristic of electromyographic activity. The most pronounced changes in the amplitude of movements of the hip joint were revealed. Effects of multisegmental spinal cord stimulation in regulation of interlimb synergy were examined. The results can be used to develop the approach for neurorehabilitation of patients with impaired motor functions.

We compared the effect of electric subcutaneous stimulation and epidural spinal cord stimulation to reactivate locomotor abilities of chronic spinal rats. We trained spinalized rats to walk bipedally on a treadmill with support of body weight for 5 days a week for 20-30 minutes while stimulating subcutaneously or epidurally at 40Hz. The dynamical changes of locomotor abilities induced by subcutaneous and epidural electrical stimulation and their effect on the neuronal spinal structures were similar. After 3 weeks, single (L2 or S1) stimulation at 1 Hz induced motor evoked responses in m.tibialis ant. and m.gastrocnemius med., while simultaneous rhythmic stimulation (L2 and S1) at 40 Hz initiated in a few steps on the moving treadmill belt. After 9 weeks of training more pronounced rhythmic pattern of muscle activity was observed, and this coincided with appearаnce of the polysynapticspinal cord reflexes. Administration of non-selective serotonin receptors agonist- quipazine facilitated the polysynaptic activity and support the view that the spinal circuitry can be modulated by serotonergic agonists.

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.

Using studies of the right and left hemisphere’s specialization for positional and vector coding, we analyzed the errors made by right- and left-handers while reproducing sequences of right and left hand movements in a task that activates vector coding by changing the order of movements in memorized sequences. The task was performed first with one hand (starting) and then with the other (continuing). Both right- and lefthanders were found to use information about previous movements of the starting hand only when the dominant hand was starting. After changing the hand, right-handers used information about previous movements of the continuing hand, while left-handers did not. The results were compared with data from earlier experiments wherein positional coding was activated. The comparison showed that vector coding was predominantly involved in memorizing sequences of movements made by the dominant hand, while positional coding was used in the case of the opposite hand in both right- and left-handers. Patterns of errors after changing the hand differed between right- and left-handers, and the conclusion was made that skills are transferred in different ways in right- and left-handers, depending on the type of coding.

An important stage in learning, i.e., the acquisition of a new skill, is the repetitive reproduction of a sequence of movements, which plays a significant role in the formation of motor stereotypies. Two groups of right-handed subjects reproduced (6–10 repeats) sequences of movements guided by the experimenter, sequences consisting of six positions, first with the right hand (RH) and then with the left hand (LH) or vice versa. In series 1, an unfamiliar random sequence was reproduced; series 2 and 3 involved reproduction of modified sequences whose elements were in the same positions but in a different order. The processes of reproduction proceeded similarly for the RH and LH. Learning of the modified sequence was different: regardless of order of presentation, information about the positions of the elements of the sequence was used only when the LH performed the task first. This information was not used when the LH operated after the RH or when the RH performed the task. Thus, the means of encoding information activated on operation by the LH promoted learning of the position memorization task, while that activated by the RH interfered. This appears to be linked with the predominant roles of the right hemisphere in encoding positions and in motor learning processes.

The errors of right- and left-handers were analyzed when they performed memorized sequences by right or the left hand during the task that activates positional coding: after six to ten times, the order of movements changed (the positions remained the same during the task). The task was at first performed by one (initial) hand, right or left, and then by the contralateral (continuing) hand; there were two groups of right- handers and two groups of left-handers. It was found that the pattern of errors during the task performance by the initial hand was similar in right- and left-handers both for the dominant and subdominant hands. Information about the previous positions after changing the order of elements is used in the sequences for subdominant hands and not used in the sequences for dominant hands. After changing the hand, right- and left-handers exhibited different patterns of errors. Thus, the errors of right- and left-handers are symmetrical at the early stages of task performance, while the transfer of this motor skill in right and left-handers occurs in different ways.