[The distinctive features of EMG-activity in early age children with movement disorders].

The purpose of this work was the study of neuromuscular characteristics of healthy infants and infants with movement disorders by method of surface electromyography. 76 children at the age from 6 months till 3 years participated in the investigation: 61 with movement disorders (13--with ataxic form of cerebral palsy (CP), 48--with spastic form of CP) and 15 without movement disorders. Passive flexing and extending of knee and hip joints was conducted to the child in a recumbent position, EMG activity of the basic muscles groups of a hip and a shin was recorded. Characteristic properties of electromyographic activity were assessed with wavelet transform and subsequent analysis of obtained time dependencies. As a result of work the parameters connected with diagnosis of infants with movement disorders were revealed.

[The dependence of motor response time in discrimination task on the type of available visual information].

The interaction of proprioceptive and visual afferentation was studied in motor task for discrimination of weights of falling objects. The availability of visual information decreased the time of motor response but to different extent depending on the kind of this information. The shortening of response time was significantly greater when subject have seen the beginning of real fall that when he simply seen the control LED signaling the release of object by electromagnet. So, subject accomplishes the task of discrimination of light and heavy object more efficiently if he sees the real falling object. This may be due to the capacity of CNS to predict the time of the impact more accurately when subject observe the initial part of real trajectory and not just an abstract visual signal.

[Oscillations of upper and lower body segments in the sagittal plane during standing: spatial-temporal interrelationships].

The balance control in the sagittal plane during standing without visual feedback has been studied in the context of the notion that a human body can be presented as a two-segment inverted pendulum. The oscillations of the center of pressure and of upper and lower segments were recorded for 2 min (ten records, seven volunteers). It was shown that the correlation coefficients and dynamical similarity between the oscillation of the upper segment and the center of pressure are significantly higher than between the lower segment and the center of pressure. The dynamic similarity between the oscillations of the upper segment in different records are higher than between the oscillations of the lower one, which supposedly is connected with the necessity of the stabilization of the head in space during standing. The oscillations of the lower segment occurred with a delay of 16.2 +/- 9.0 ms relative to the oscillations of the upper segment. At the same time, the distribution of the delays has maximum at zero (it is asymmetrical), indicating that two strategies of balance control are used during quiet standing, which are described by a one-segment and a two-segment model of inverted pendulum.

[Nonlinear analysis of the dynamics of the human balance control system during fixation and smooth pursuit of visual target].

The similarity between the dynamics of the human balance control system in the frontal and sagittal planes during the fixation of visual stimulus and smooth pursuit of its sinusoidal movements in the horizontal plane with a frequency of 0.1 or 0.01 Hz (so-named fast and slow pursuit) has been investigated by the nonlinear method of analysis. The experiments were carried out according to the notion that it is possible to describe the process of orthograde standing by a two-segment model--upper and lower segments which are connected by a hip joint (other joints were fixed). It was shown that during fixation the similarity between the dynamics of orthostatic control system in the frontal plane is higher than in the sagittal plane. A slow pursuit does not influence the similarity, but a fast one decreases the similarity in the frontal plane. The indices of similarity between the dynamics of the system in the sagittal plane for all the conditions are close and do not differ significantly. The changes in similarity during fast pursuit are supposed to be connected with the different inertia of eyes and body movements. The differences between dynamic similarity in the frontal and sagittal planes are probably connected with the peculiarities of both balance control during joint fixation and AP-ML control (Winter et al., 1993) under conditions investigated.