1Pavlov Institute of Physiology of the Russian Academy of Sciences, St.-Petersburg, Russia; 2N.P. Behtereva Institute of Human Brain of the Russian Academy of Sciences, St.-Petersburg, Russia
Each voluntary human movement is initiated and adjusted by nervous system and represents a motor output of its integrative activity. In order to understand as occurs in CNS the movement's "construction", the bio mechanics during second half XX of century tried to calculate the controlling forces and moments out the trajectories of purposive movements acting in the locomotor limb joints and are ensuring a performance of the central motion programs. On the basis of such researches N. A. Bernstein has shown necessity of a multilevel organisation of motor control system, ring regulation and recurrent afferent pathways for realization of purposeful labour and sports movements. However, the organization of activity at all levels of motor control system during the motion acting remains hypothetical. The modern methods of visualization can show only participation of structures of a brain in any activity. Take into account necessity of ring regulation; in order to reveal parameters of the activity circulating in closed circuits, we used a sustained isometric effort as an instance of voluntary movement. At sustaining isometric effort, there is an increase of excitation in all structures of motor control system, which is proportional to force. The cyclic activity formed with participation of each level in contours, closed on motoneurons that activated muscle contraction, should be reflected in parameters of isometric effort as CNS motor output. The modern mathematical analysis of the sequential time series has extracted in sustained isometric effort the properties of central controlling commands descending to motoneuron pools. After additional transformations of results of time series decomposition the selected components characterize, is supposed, activity of different levels of regulation of motor control system in amplitude-frequency parameters. Meaning of frequency appropriate to sites of maxima in decomposition curve, characterized the cyclic activity formed with participation of a certain level of muscle contraction regulation. The revealed frequencies allow ascribing them to segmental regulation level, to level of voluntary control with participation of pyramidal way or to levels involuntary (automatic) regulation, associated with activity in extrapyramidal tracts. Frequencies distribution patterns allow to present integrative activity in structures of a motor control system, at least, at voluntary control by isometric effort.
Scientific Program of Presidium of Russian Academy of Sciences «Fundamental sciences - for medicine» supports the research.