time series analysis
diagnostics of the motor control system activity
Romanov S.P., Alexanyan Z.A.
The purpose of the study is to use the isometric force to evoke the increased activity in motor control structures for subsequent frequency analyzing of motor descending drives causing muscles contraction. Out of all organism systems the CNS structures are most hard-to-reach for study of their activity and require the special approaches for noninvasive monitoring of their functional state. The increased opportunities of influence on the mediator systems of the brain necessitate objective estimation of a functional state of CNS and the control of efficiency of therapeutic procedures, and also open new ways of study of the central motor control mechanisms and organism behavior as a whole. In clinical practice for diagnostics of movement disorders of the central origin the tremor registration and analysis of its parameters are widely used, and the detected frequencies of oscillations of moving body parts serve as the diagnostic criteria of a motor control system dysfunction. Tremor as a movement is the result of muscles contraction forces. Why not analyze directly the parameters of forces but not tremors? By sustaining the isometric effort, examinee or patient can voluntarily activate the structures of their own motor control system proportionally his/her force. That allows to receive the additional information on features of motor control and to objectively estimate parameters of involuntary component that describe endogenous activity of motor control system. Such approach has neurophysiological substantiation basing on representations about structural organization of motor control system and of principles of closed-loop regulation (Bernstein N.A., 1967) and on the property of nervous system to homeostating of the cyclic activity in the closed structures (Romanov, 1989). By arising on different levels of motor system the cyclic activities descend to segmental pools of motoneurons and can be recorded through muscle contraction force. The objectivity of registration of force has allowed us to apply methods of time-series analysis (SSA) to the analysis of sustained isometric effort. In this case, analyzing parameters of voluntary isometric effort, we actually can estimate a functional state of the central (motor) nervous system, i.e. its integral activity formed in various frequencies ranges by different levels of motor system, not only at pathological state at patients, but at healthy individuals too. The distinctions in integral activity of the healthy man and patient with the diagnosis of Parkinson's disease, and also the changes in gain-frequency parameters of activity on a background of L-dopa therapy are shown. Method of testing and recording of isometric effort is simple enough and not requires imposing any gauges on the body of investigated and of special trained medical staff. The important advantage of the method is standardization of effort (kg), under which the integral activity is analyzed; and its clearly recognized parameters represent the objective biometric characteristic of functional state of CNS.