PubMed Health⌕ Search

Biomedical subjects

Yu P Gerasimenko

Publications and source records attributed to Yu P Gerasimenko.

7 recordsLinked to original sources
PubMed2007

Significance of peripheral feedback in the generation of stepping movements during epidural stimulation of the spinal cord.

Acute experiments on decerebrate and spinal cats were performed to study the role of the peripheral afferent input from hindlimb receptors in forming the locomotor pattern during epidural stimulation of the spinal cord. Evoked electromyographic activity in the muscles of the hindlimbs was analyzed, along with the kinematic parameters of stepping movements. Epidural stimulation (20-100 microA, 5 Hz) of segments L4-5 of the spinal cord was found to elicit well coordinated walking in the hindlimbs on a moving treadmill band. When the support conditions were changed (non-moving treadmill, unsupported position), epidural stimulation initiated walking with an unstable rhythm. This was associated with a change in the overall nature of the locomotor pattern and the internal structure of the stepping cycle. Alteration of the direction of movement of the treadmill band led to the appearance of backward walking. An increase in the speed of movement of the treadmill band increased the stepping frequency, mainly due to decreases in the extensor phase. Epidural stimulation applied 2-4 h after complete transection of the spinal cord at the T8-T9 level could elicit stepping movements, but only when the treadmill was moving. The role of peripheral feedback in generating the locomotor pattern in conditions of complete disconnection from supraspinal control increased significantly. These data show that peripheral feedback during epidural stimulation of the spinal cord can define the properties of the motor output.

Animals↗
PubMed2005

Hindlimb stepping movements in complete spinal rats induced by epidural spinal cord stimulation.

The locomotor ability of the spinal cord of adult rats deprived of brain control was tested by epidural spinal cord stimulation. The studies were performed on six rats that had a complete spinal cord transection (T7-T9) and epidural electrode implantations 2-3 weeks before testing was initiated. The stimulating epidural electrodes were implanted at the T12-L6 spinal segments. Epidural electrical stimulation of the dorsal surface of the spinal cord at frequencies between 1 and 50 Hz and intensities between 1 and 10 V without any pharmacological facilitation was used. Stimulation at each of the lumbar spinal cord segments elicited some rhythmic activity in the hindlimbs. However, stimulation at most segmental levels usually evoked activity in only one leg and was maintained for short periods of time (< 10s). Bilateral hindlimb locomotor activity was evoked most often with epidural stimulation at 40-50 Hz applied at the L2 segment. A necessary condition for initiation of locomotor activity was providing a specific amount (at least 5%) of body weight support. Therefore, the rat spinal cord isolated from brain control is capable of producing bilateral stepping patterns induced most readily by epidural stimulation applied at the L2 spinal segment. Furthermore, the induced stepping patterns were dependent on sensory feedback associated with weight bearing.

Animals↗
PubMed2005

Formation of locomotor patterns in decerebrate cats in conditions of epidural stimulation of the spinal cord.

Acute experiments on decerebrate cats were performed to study the mechanism of formation of the locomotor pattern in conditions of epidural stimulation of the spinal cord. These studies showed that only segments L3-L5 contributed to generating the stepping pattern in the hindlimbs. At the optimum frequency (5-10 Hz) of stimulation of these segments, formation of electromyographic burst activity in the flexor muscles was mainly due to polysynaptic reflex responses with latencies of 80-110 msec. In the extensor muscles, this process involved the interaction of a monosynaptic reflex and polysynaptic activity. In epidural stimulation, the stepping pattern was specified by spinal structures, while peripheral feedback had modulatory influences.

Animals↗
PubMed2003

Initiation of locomotor activity in spinal cats by epidural stimulation of the spinal cord.

Acute and chronic experiments on lower spinal (T10-T12) cats were performed to investigate the effects of epidural stimulation of the dorsal surface of the spinal cord on the initiation of locomotor activity. A zone located at the border between segments L4 and L5 was identified, stimulation of which induces locomotor activity. The parameters of epidural stimulation of the spinal cord effective in activating the stepping movement generator were identified. Epidural stimulation leading to the initiation of movement activity was shown to depend on intracentral and peripheral mechanisms activating the segmental, intersegmental and propriospinal reflex systems of the spinal cord. A leading role was demonstrated for the propriospinal system of the dorsolateral funiculi in activating the generators of stepping movements in epidural stimulation of the spinal cord.

Animals↗
PubMed2003

Method for studying the processes maintaining equilibrium at rest standing.

According to current concepts, two processes are responsible for the maintenance of body equilibrium: shifts of the reference point caused by changes in the posture and stabilization of oscillations of the center of mass relative to this point. Exact changes in these processes occurring at various forms of locomotor disorders remain unclear. We proposed an original mathematical method allowing separate evaluation of these two processes responsible for the maintenance of body equilibrium.

Biomechanical Phenomena↗
PubMedDate not supplied

Control of locomotor activity in humans and animals in the absence of supraspinal influences.

Electrical epidural stimulation of the dorsal surface of the spinal cord at the level of the second lumbar segment induced step-like movements accompanied by the corresponding electromyographic activity in the leg muscles in patients lacking supraspinal influences as a result of vertebral trauma. Triggering of stepping movements was shown to occur with particular stimulation parameters. The results provide evidence that in humans, as in other mammals, the spinal cord contains a network of interneurons acting as generators of stepping movements and producing coordinated patterns of movement activity. Experiments on chronic spinal cats demonstrated the leading role of the propriospinal system of the spinal cord inactivating the spinal generators of stepping in response to epidural stimuli.

Adult↗