[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.

[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.

[Analysis of locomotor activity in decerebrated cats during electromagnetic and epidural electrical spinal cord stimulation].

It was shown that the epidural and the electromagnetic tonic stimulation with frequency 5 Hz applied to the lumbal as well as to the cervical region of the spinal cord enabled stepping on a moving treadmill belt in decerebrated cats. It was found that there were differences in initiation of the stepping movements during epidural and electromagnetic stimulation depending on the region of spinal cord stimulation. Stimulation at frequency of 0.3 Hz induced single reflex responses in the anterior and posterior limbs. On the basis of analysis of the response structure it was concluded that the locomotor ability during epidural and electromagnetic stimulation depended on the degree of polysynaptic pathways activation. The hypothesis about stepping pattern generator activation through the dorsal roots during epidural stimulation and more direct activation of neuronal locomotor networks in the case of electromagnetic spinal cord stimulation is discussed.

[Novel method for activation of the locomotor circuitry in human].

We examine the possibility for activation of the involuntary locomotion of the lower limbs by spinal electromagnetic stimulation (ES). The subject laid on the left side. The legs are supported in a gravity-neutral position by special mounting that to provide horizontal rotation in the hip, knee and ankle. ES (3 Hz and 1.56 Tesla) at the T11,-T12 vertebrae induced involuntary locomotor-like movements in the legs. The latency from the initiation of ES to the first EMG burst compoused 0.68 +/- 1.0 s and it shortened at increasing of the frequency ES from 3 Hz to 20 Hz. Thus, the spinal ES can unduce the activation of the locomotor movements in human.

[Mechanisms of stepping rhythm formation during epidural spinal cord stimulation in decerebrated and spinal cord transected cats].

The mechanisms of stepping pattern formation during epidural spinal cord stimulation in decerebrated and chronically spinal cord transected cats have been investigated. The features of the stepping performance in hindlimb muscles depending on the parameters of epidural stimulation and afferent input were determined. It was shown that, at nonoptimal parameters of stimulation, stepping movements are not induced. In response to the stimulation, reflectory muscle responses are evoked only. Epidural stimulation with optimal parameters induces coordinated stepping movements in hindlimbs with normal rhythm (0.8-1 Hz), which is accompanied by the electromyographic bursting activity of the corresponding muscles. In decerebrated cats, the formation of electromyographic bursts occurs due to the modulation of early responses and the late polysynaptic activity. In chronically spinal cord transected cats, this process is provided mainly by the amplitude modulation of early responses. The formation of the stepping pattern in decerebrated cats with the participation of spinal interneurons responsible for the polysynaptic activity allows one to perform its correction on the basis of the processing of afferent signals. The activation of this system in chronically spinal cord transected cats can be realized by afferent stimulation alone.

[Initiation of locomotion in decerebrated cat by using of impulse magnetic field projected onto the spinal cord segments].

The motor effects induced by impulse magnetic field (IMF) applied to lumbar as well as to cervical enlargements in decerebrated cat were studied. The magnetic coil with diameter 8 cm was placed on the distance 1-2 cm over the spinal cord. Single magnetic spinal cord stimulation with intensity 0.5-1 Tesla as well as continuous magnetic stimulation with frequency of 1 Hz and intensity 0.5 Tesla was performed. Single magnetic stimulation of lumbar enlargement elicited reflex responses in proximal and distal hind limb muscles. Continuous stimulation induced the locomotor activity in hind limbs on moving treadmill belt by activation of neuronal spinal locomotor networks (generator of stepping movements). The stimulation of lumbar enlargement involved into the locomotor activity only hind limbs. Continuous magnetic stimulation of cervical enlargerment evoked coordinated stepping movements in fore- and hind limbs. Initially stepping movements raised in hind limbs and then in forelimbs. After cessation of magnetic stimulation some coordinated stepping movements were observed. Thus, for the first time we showed a possibility to induce the locomotor activity in decerebrated cat by magnetic stimulation. The obtained results demonstrate the ability of non-invasive mode of neuronal spinal locomotor network activation. This approach opens new perspectives for using magnetic stimulation in clinical practice.