A New Technology for Recovery of Locomotion in Patients after a Stroke.

Neural networks in the spinal cord can generate the walking pattern and control posture in the absence of supraspinal influences. A technology using transcutaneous electrical spinal cord stimulation (tSCS) was created. During walking, tSCS activated spinal locomotor networks, as well as leg flexor/extensor motor pools in the swing/stance phases, respectively. It was assumed that the use of this technology in subjects with locomotion disorders would improve walking. Patients with hemiparesis were studied 3-11 months after stroke, the duration of the course was 2 weeks. Patients of the main and control groups received standard therapy and rehabilitation using the technology; in the control group, sham tSCS was used. After the course, minimal clinically important differences in walking parameters were achieved in the main group, in contrast to the control group. The developed technology is an effective means of restoring walking in patients with hemiparesis.

Memorization of Sequences of Movements of the Right or the Left Hand by Right- and Left-Handers: Vector Coding.

In order to test the hypothesis of hemisphere specialization for different types of information coding (the right hemisphere, for positional coding; the left one, for vector coding), we analyzed the errors of right and left-handers during a task involving the memorization of sequences of movements by the left or the right hand, which activates vector coding by changing the order of movements in memorized sequences. The task was first performed by the right or the left hand, then by the opposite hand. It was found that both'right- and left-handers use the information about the previous movements of the dominant hand, but not of the non-dom" inant one. After changing the hand, right-handers use the information about previous movements of the second hand, while left-handers do not. We compared our results with the data of previous experiments, in which positional coding was activated, and concluded that both right- and left-handers use vector coding for memorizing the sequences of their dominant hands and positional coding for memorizing the sequences of non-dominant hand. No similar patterns of errors were found between right- and left-handers after changing the hand, which suggests that in right- and left-handersthe skills are transferred in different ways depending on the type of coding.

[Identification of Spatial Coding Schemes by Errors Distribuition of Human Memory].

The error distributions of sensory screen touches at kinesthetically memorization and reproduction of visual stimuli containing Muller-Lyer illusion and neutral stimuli were investigated. One group of right-handers begins the task with the right hand and continues with the left one, while the other group--vice versa. It was shown that the errors are distributed either exponentially (with the maximal amount of small errors) either with the maxima at the 2nd bin. The number of errors distributions decaying exponentially is higher for the group beginning the task with the right hand. The errors distributions of touches on the upper segment by the right hand decay exponentially faster than other distributions. Comparison of these data with the simulation results supports the hypothesis of specific for the right and left hemisphere positional and vector coding schemes at human memory.

[Learning and Repetive Reproduction of Memorized Sequences by the Right and the Left Hand].

An important stage of learning a new skill is repetitive reproduction of one and the same sequence of movements, which plays a significant role in forming of the movement stereotypes. Two groups of right-handers repeatedly memorized (6-10 repetitions) the sequences of their hand transitions by experimenter in 6 positions, firstly by the right hand (RH), and then--by the left hand (LH) or vice versa. Random sequences previously unknown to the volunteers were reproduced in the 11 series. Modified sequences were tested in the 2nd and 3rd series, where the same elements' positions were presented in different order. The processes of repetitive sequence reproduction were similar for RH and LH. However, the learning of the modified sequences differed: Information about elements' position disregarding the reproduction order was used only when LH initiated task performing. This information was not used when LH followed RH and when RH performed the task. Consequently, the type of information coding activated by LH helped learn the positions of sequence elements, while the type of information coding activated by RH prevented learning. It is supposedly connected with the predominant role of right hemisphere in the processes of positional coding and motor learning.

[Mathematical model of the hindlimbs control during cat locomotion with balance].

The musculoskeletal model of cat's hind limbs, capable to step while maintaining balance, was developed using the MatLab. The skeletal part of the model (spine, pelvis, hips, shanks, foots) was created at SimMechanics. The joint in the spine attachment to the support and hip joint have three degrees of freedom. Knee and ankle joints have one degree of freedom. The pelvis is rigidly connected to the spine. The control of the skeleton's segments is done by six groups of muscles (flexors and extensors of hips, knees and ankles), modeled using the package VirtualMuscle. The generalized lateral force exerted on the spine was introduced to compensate insecure lateral deviations. Experimental verification of the model realness have shown that its locomotor characteristics (e. g., muscles activation patterns, oscillation period of pelvis, correlation between step length and maximal lateral shift of pelvis) do not significantly differ from the locomotion of decerebrate cats. The simulation confirms the key role of lateral force evolved by paravertebral and abductor-adductor muscles in the control of lateral stability during locomotion.

[Memorization of Sequences of Movements of the Right and the Left Hand by Right- and Left-Handers].

We analyzed the errors of right- and left-handers when performing memorized sequences by the left or the right hand during the task which activates positional coding: after 6-10 times the order of movements changed (the positions remained the same during all task). The task was first performed by one ("initial") hand, and then by another one ("continuing"); there were 2 groups of right-handers and 2 groups of left-handers. It was found that the pattern of errors during the task performance by the initial hand is similar in right- and left-handers both for the dominant and non-dominant hand. The 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 ones. After changing the hand, right- and left-handers show different patterns of errors ("non-symmetrical"). 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.

[Age differences in memorizing of sequence of movements of leading and subdominant hand].

Age-specific features of motor short-term memory were studied. Two groups of right-handed volunteers (18-25 and 35-60 years old) reproduced the memorized sequence of six movements by the right hand or by the left one. The mean values of erroneous movements are shown to be significantly higher in elder group, demonstrating the age-dependent reduction of motor short-term memory capacity. More detailed analysis of reproduction of separate elements of the sequence demonstrates that the age-dependent increasing of error value is significant for the leading right hand, but not for the subdominant left one. The data obtained are consistent with the evidences about age-dependent reduction of hemispheric asymmetry and about more pronounced reduction of the accuracy of the movements of the leading hand. According to the hypothesis about hemispheric specialization in coding of movement information (right hemisphere specialization on absolute positional coding, the left one--on relative vector coding, i.e. coding of the movements) the data suppose the age-dependent reduction of the left-hemisphere system of relative coding. The reduction of memory capacity apparently can be explained by the reduction of role of the left hemisphere in functioning of the short-term motor memory owing to age-dependent reduction of hemispheric asymmetry.

Structure of internal interneuronal connections in field 17 of the cat cerebral cortex.

The spatial distribution of horizontal internal connections in field 17 of the cat cortex was studied after microiontophoretic application of horseradish peroxidase to individual cortical columns. Cluster analysis of the distribution of labeled cells in the superficial layers in the tangential plane of the cortex was performed. Field 17 included 7 +/- 1 clusters of up to five cells. Clusters were distributed into two layers, separated by 1.2 +/- 0.3 mm. The distance between the centers of the clusters forming rows was 0.8 +/- 0.3 mm. The spatial characteristics of the grouping of cells sending axons into the cortical column were compared with published data based on optical visualization of the activity of neurons in orientational and eye-dominant columns of the visual cortex. It is suggested that columns in field 17 are associated with 6-8 hypercolumns, though only with a single type of neuron within these hypercolumns, in terms of eye dominance and orientational preference.

Regular structural organization of intrahemisphere interzonal connections in the visual cortex of the cat.

The aim of the present work was to conduct a morphometric analysis of the cluster organization of neurons forming interzonal corticocortical connections in the visual cortex. The investigations used a method based on retrograde transport of horseradish peroxidase and mathematical analysis of the spatial distribution of labeled cells. Measurements yielded the following quantitative characteristics of the cell distribution--the volume and linear sizes of clusters, the distance between the centers of gravity of clusters, and the periodicity in the distribution of clusters along the cortical surface. Age-related features of the distribution of cells giving rise to cortical interzonal connections were identified. The experiments showed that the pattern of the cluster organization typical of adult cats was formed by the end of the second month of life. Quantitative differences in the spatial organization of neuron groups in the cortex of visual fields 17 and 18 were demonstrated.