Previously, we developed a method for objective assessment of the state of proprioceptive perception of movements of the upper limb. In order to test this method for assessing the proprioceptive perception of lower limb movements, we studied the accuracy of copying with open and closed eyes a series of passive single-joint movements of the tested leg directly during their execution with the help of active movements of the other leg. Flexion-extension copying in the knee and ankle joints was studied in 30 healthy subjects for both legs and in 40 patients with unilateral stroke for the paretic leg. The accuracy of copying movements was assessed by recording the angles in the tested joint and the joint of the same name of the opposite limb using qualitative and quantitative objective indicators. It was shown that healthy subjects, both under visual control and without it, copy the passive movements of the right and left legs with high accuracy and almost simultaneously. Based on the study of the values of qualitative and quantitative indicators of copying accuracy, an objective conditional criterion for the preservation of proprioceptive perception of movements in the knee and ankle joints was formulated. In contrast to healthy subjects, in the group of patients, the results of copying with open and closed eyes were significantly different. In tests with open eyes, the copying of movements was qualitatively correct, which indicates that they understood the motor task of the test and were able to perform it with a conditionally healthy leg. In the absence of visual control, most of them either made gross errors in the transmission of the direction and number of the tested movements, or reproduced movements with a significant deterioration in accuracy (increased delays, shape distortion, etc.). It was shown that the proprioceptive perception of movements in the ankle joint was disturbed more often and more strongly than movements in the knee joint. In accordance with the developed conditional criterion of the norm, in 69% of patients there was a violation of the proprioceptive perception of movements in the knee and/or ankle joints.

Aim. Objective evaluation of proprioceptive perception of single-joint movements of the paretic arm in patients with unilateral brain damage using the method developed by us. Materials and Methods. Proprioceptive perception of pronation-supination of the forearm, flexion-extension in the shoulder, elbow and wrist joints and abduction-adduction in the shoulder and wrist joints was tested in 23 patients with right-sided and 17 patients with left-sided brain damage. The subject with his eyes closed was made to perform a series of passive cyclical test movements, during which he had to copy them with active movements of the other arm. Joint angles were recorded in the test joint and the same joint ofthe other arm. The integrity of proprioceptive sensitivity was judged by the degree of similarity between “active” and “passive” movements estimated by means of objective qualitative and quantitative indicators. Results. Proprioceptive deficiency was detected in 83% of patients with lesion in the right and in 71% of patients with lesion inthe left hemisphere, while the proportion of test movements that revealed a violation of proprioceptive perception was 1.4 times higher in the right-hemisphere patients than in the left-hemisphere patients. A significant part of proprioceptive impairments, – 80% when testing movements of more distal and 29% – proximal segments of the arm, was detected by the presence of qualitative copying errors. Conclusions. The method used made it possible to identify proprioceptive deficits in more than half of patients with damage to both the right and left hemispheres. Proprioceptive perception of movements of the distal arm segment suffered more often and was more pronounced than the proximal one. A significant part of distal segment proprioception disorders manifested themselves in the form of gross qualitative copying errors, which can be detected visually during testing, even without the use of recording equipment.

Motor activity of infants becomes detectable as early as the first months (9–10 weeks) of fetal development. These movements constantly change during maturation of the fetus, are preserved after birth, and are called general movements. The complexity and variability of movements is a criterion for the normal motor development of infants in the postnatal period. Disturbances in maturation of the nervous system are reflected in abnormal patterns of general movements, and the patterns thus make it possible to diagnose perinatal brain lesions early. This is especially important in the case of preterm infants, who are at higher risk of developing neurological and motor disorders. This review describes the main types of general movements characteristic of normal motor development, the atypical motor patterns that have a predictive value for early prediction of cerebral palsy, and the putative neural substrates that determine the development of normal and abnormal general movements. Various methods are available for assessing general movements, including both qualitative techniques, which are based on visual assessment of motor patterns, and quantitative methods, which employ technologies of automated general movement recognition and analysis.

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.

Testing of sensory-motor performance and motor rehabilitation training in post-stroke patients are often executed in lying position. At the same time, influence of the body position on proprioceptive perception is poorly studied. In this study, we have investigated proprioceptive perception of single-joint arm movements in 10 healthy subjects and 17 post-stroke patients with unilateral arm paresis in the sitting and lying positions using the method we developed. Movements of flexion–extension in shoulder, elbow and wrist joints and abduction–adduction in shoulder and wrist joints were tested. The subjects were made to perform a series of the passive single-joint movements with the eyes closed and had to copy these movements simultaneously by active movements of another arm. We recorded the angles at the tested joint and the homonymous joint of the other arm, and the status of proprioceptive sensitivity was evaluated basing on the degree of similarity of these “passive” and “active” movements. Qualitative and quantitative indicators were used to assess the similarity. It was found that healthy subjects reproduce the passive movements without rough qualitative errors in both the sitting and lying positions. The movement reproduction was less accurate in the lying position by values of some quantitative indicators, however only 3% of trails did not match the conventional criterion for proprioceptive sensitivity intactness. On the contrary, the movement reproduction in almost half of tests in the group of post-stroke patients was performed with qualitative and quantitative errors and did not match the requirements of the conventional criterion. A deficit of proprioception was observed in 1 to 5 different test-movements in 88% of patients in the sitting position and 71% of patients in the lying position. Most frequent and rough errors in the movement reproduction were observed in distal segments of the paretic arm. It was found that the body position could have different effects on the proprioceptive perception of the same test-movement in patients: the proprioceptive perception was evaluated as intact in the sitting position and as distorted in the lying position in 14% of all test trials and vice versa it was evaluated as distorted in sitting position and as intact in lying positions in 17% of trials. Such individual differences must be considered when choosing conditions for motor rehabilitation procedures in patients with paresis of the arm.

Locomotion of mammals, including humans, is based on the rhythmic activity of spinal cord circuitries. The functioning of these circuitries depends on multimodal afferent information and on supraspinal influences from the motor cortex. Using the method of transcranial magnetic stimulation (TMS) of arm muscle areas in the motor cortex, we studied the motor evoked potentials (MEP) in the upper arm muscles in stationary conditions and during voluntary and vibration-evoked arm movements. The study included 13 healthy subjects under arm and leg unloading conditions. In the first series of experiments, with motionless limbs, the effect of vibration of left upper arm muscles on motor responses in these muscles was evaluated. In the second series of experiments, MEP were compared in the same muscles during voluntary and rhythmic movements generated by left arm m. triceps brachii vibration (the right arm was stationary). Motionless left arm vibration led to an increase in MEP values in both vibrated muscle and in most of the non-vibrated muscles. For most target muscles, MEP was greater with voluntary arm movements than with vibration-evoked movements. At the same time, a similar MEP modulation in the cycle of arm movements was observed in the same upper arm muscles during both types of arm movements. TMS of the motor cortex significantly potentiated arm movements generated by vibration, but its effect on voluntary movements was weaker. These results indicate significant differences in the degree of motor cortex involvement in voluntary and evoked arm movements. We suppose that evoked arm movements are largely due to spinal rather than central mechanisms of generation of rhythmic movements.

The phenomenon of reproduction of the series of passive single-joint movements in the tested arm by the contralateral arm just in the course of passive movements with no visual control was studied in 35 healthy subjects and 13 post-stroke patients in order to develop a new method for objective assessment of sense of the arm motion for the detection of proprioceptive deficit and for monitoring of the changes in proprioception during rehabilitation. We examined the reproduction of flexion–extension at the elbow and wrist joints, abduction–adduction at the wrist joint and the forearm pronation–supination in both right and left arms in healthy subjects and in the affected arm in post-stroke patients. Displacements of the angles in the tested joint and a homonymous joint of the other arm were acquired by means of video recording system, goniometers, or 9-DoF inertional-magnetometric sensors. Qualitative and quantitative indicators were evaluated to assess the similarity of the passive and active movements. It has been found that the healthy subjects are able to actively reproduce the repeated passive movements at different joints of either the left or right tested arm almost simultaneously and with quite accurate reproduction of an amplitude and shape of movement. At the same time, most of post-stroke patients reproduce movements either with qualitative errors demonstrating incorrect location or wrong estimation of direction or number of repeated test movements, or with significant reduction of accuracy (increased latency or shape distortion). We proposed a method for the assessment of movement proprioception at individual joints. The procedure is easy and convenient for both physicians and patients. It does not require special heavy equipment and can easily be performed under different conditions in a wide range of patients.

The effect of arm movements and movements of individual arm joints on the electrophysiological and kinematic characteristics of voluntary and vibration-triggered stepping-like leg movements was studied under the conditions of horizontal support of the upper and lower limbs. The horizontal support of arms provided a significant increase in the rate of activation of locomotor automatism by noninvasive impact on tonic sensory inputs. The addition of active arm movements during involuntary stepping-like leg movements led to an increase in the EMG activity of hip muscles and was accompanied by an increase in the amplitude of hip and shin movements. The movement of the shoulder joints led to an increase in the activity of hip muscles and was accompanied by an increase in the amplitude of hip and shin movements. Passive arm movements had the same effect on induced leg movements. The movement of the shoulder joints led to an increase in the activity of hip muscles and an increase in the amplitude of movements of knee and hip joints. At the same time, the movement of forearms and wrists had a similar facilitating effect on the physiological and kinematic characteristics of rhythmic stepping-like movements, but influenced the distal segments of legs to a greater extent. Under the conditions of subthreshold vibration of leg muscles, voluntary arm movements led to activation of involuntary rhythmic stepping movements. During voluntary leg movements, the addition of arm movements had a significantly smaller impact on the parameters of rhythmic stepping than during involuntary leg movements. Thus, the simultaneous movements of the upper and lower limbs are an effective method of activation of neural networks connecting the rhythm generators of arms and legs. Under the conditions of arm and leg unloading, the interactions between the cervical and lumbosacral segments of the spinal cord seem to play the major role in the impact of arm movements on the patterns of leg movements. The described methods of activation of interlimb interactions can be used in the rehabilitation of post-stroke patients and patients with spinal cord injuries, Parkinson’s disease, and other neurological diseases.

The coordination between arms and legs during human locomotion shares many features with that in quadrupeds, yet there is limited evidence for the central pattern generator for the upper limbs in humans. Here we investigated whether different types of tonic stimulation, previously used for eliciting stepping-like leg movements, may evoke nonvoluntary rhythmic arm movements. Twenty healthy subjects participated in this study. The subject was lying on the side, the trunk was fixed, and all four limbs were suspended in a gravity neutral position, allowing unrestricted low-friction limb movements in the horizontal plane. The results showed that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long-lasting isometric voluntary effort, Kohnstamm phenomenon) could evoke nonvoluntary rhythmic arm movements in most subjects. In ∼40% of subjects, tonic stimulation elicited nonvoluntary rhythmic arm movements together with rhythmic movements of suspended legs. The fact that not all participants exhibited nonvoluntary limb oscillations may reflect interindividual differences in responsiveness of spinal pattern generation circuitry to its activation. The occurrence and the characteristics of induced movements highlight the rhythmogenesis capacity of cervical neuronal circuitries, complementing the growing body of work on the quadrupedal nature of human gait.

During natural human locomotion, neural connections are activated that are typical of regulation of the quadrupedal walking. The interaction between the neural networks generating rhythmic movements of the upper and lower limbs depends on tonic state of each of these networks regulated by motor signals from the brain. Distortion of these signals in patients with Parkinson’s disease (PD) may lead to disruption of the interlimb interactions. We examined the effect of movements of the limbs of one girdle on the parameters of the motor activity of another limb girdle at their joint cyclic movements under the conditions of arm and leg unloading in 17 patients with PD and 16 healthy subjects. We have shown that, in patients, the effect of voluntary and passive movements of arms, as well as the active movement of the distal parts of arms, on the voluntary movement of legs is weak, while in healthy subjects, the effect of arm movements on the parameters of voluntary stepping is significant. The effect of arm movements on the activation of the involuntary stepping by vibrational stimulation of-legs in patients was absent, while in healthy subjects, the motor activity of arms increased the possibility of involuntary rhythmic movements activation. Differences in the effect of leg movements on the rhythmic movements of arms were found in both patients and healthy subjects. The interlimb interaction appeared after drug administration. However, the effect of the drug was not sufficient for the recovery of normal state of the neural networks in patients. In PD patients, neural networks generating stepping rhythm have an increased tonic activity, which prevents the activation and appearance of involuntary rhythmic movements facilitating the effects of arms on legs.

The mechanism of interactions between receptor activation in the musculoskeletal system and stimulation of the spinal cord in the regulation of locomotor behavior was studied in healthy subjects. Afferent stimulation was tested for effect on the patterns of stepping movements induced by percutaneous stimulation of the spinal cord. A combination of percutaneous spinal cord stimulation and vibratory stimulation was shown to increase the amplitude of leg movements. It was demonstrated that vibratory stimulation of limb muscles at a frequency of less than 30 Hz can be used to control involuntary movements elicited by noninvasive stimulation of the spinal cord.

Болезнь Паркинсона (БП) – прогрессирующее нейродегенеративное заболевание, одним из основных симптомов которого являются гипертонус и возникающие при повышенной жесткости мышц затруднения при выполнении шагательных движений. У 25 пациентов с легкой и умеренной стадиями БП (от 1 до 3 по шкале Хен и Яра, средний возраст 61 ± 9 лет) и у 22 здоровых испытуемых того же возраста исследовали биомеханические (жесткость) и электрофизиологические (реакции укорочения) характеристики мышц бедра и голени в условиях разгрузки ног при пассивном сгибании/разгибании в тазобедренном, коленном и голеностопном суставах, а также изменения тонического состояния мышц под воздействием леводофы. Проводили сравнение с аналогичными данными у здоровых испытуемых. Результаты показали существенно большую жесткость всех групп мышц ног (за исключением разгибателей стопы) у больных по сравнению со здоровыми. При пассивных движениях звеньев нижних конечностей в мышцах бедра и голени у пациентов часто наблюдались реакции укорочения (РУ), у здоровых РУ наблюдались значительно реже. У пациентов с БП в разгибателях бедра и голени, а также в мышцах сгибателях и разгибателях стопы величины РУ были значимо выше, чем у здоровых испытуемых. Лекарство существенно уменьшало жесткость сгибателей бедра, сгибателей и разгибателей колена. Реакции укорочения сохранились, хотя частота их возникновения в половине исследуемых мышц уменьшалась, и в разгибателях стопы наблюдалось значимое уменьшение величины РУ. Лекарство не оказывало существенного влияния на РУ в проксимальных мышцах. Таким образом, у больных с БП повышенная жесткость мышц проявляется в искаженных реакциях на внешние возмущения и отражается в увеличении рефлекторных ответов мышц.