2反射ループ理論による手の生理的振戦のシミュレーション(1部ヒトのバイオメカニクス)

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A new model of physiological tremor has been developed in order to establish an analytical procedure for extracting physiological information from the data of tremor frequencies. The model is basically an equation of motion composed of the second-order mechanical system and the spinal and supraspinal reflex loops. The following two parameters are introduced in the model: 1) the gain ratio of the two reflex loops (long-loop gain/short-loop gain), and 2) a characteristic frequency inversely proportional to the difference of the two delay times, which corresponds to a fixed point in the graph of the reflex term of the phase angle equation. The sustained oscillation frequencies are theoretically determined from the intersections of the curves of the mechanical and reflex terms of the phase angle equation. If the gain ratio is less than unity, there are generally three intersections. It is predicted that the two lower frequencies may possibly be observed as a doublet line spectrum (frequency splitting) if they are close to each other. In order to validate the model, sustained oscillations of the hand with an added weight were measured during slow relaxing movement. Damped oscillations after a tap were also measured. The advantages of the slow relaxing movement for tremor generation are relatively large amplitude and sinusoidal wave form of the oscillations. Mechanical oscillations were selected from the damped oscillations using a criterion of half-power band width to calculate the mechanical parameters. As the model predicted, a doublet line spectrum of the sustained oscillation was observed under a specific loading condition, supporting the model and enabling us to calculate the reflex parameters. The best fitting reflex parameters including the delay times and the gain ratio of the two reflex loops were obtained using a least-square criterion. The long-and short-loop delay times are estimated to be 71ms and 25ms, respectively, and the loop-gain ratio is less than unity. The behavior of the tremor frequency was simulated as a function of the loop-gain ratio using the parameters of the hand described above. The results of the simulation reveal that the doublet line spectrum occurs in a certain range of the gain ratio when it is less than unity, and as it increases further, the frequency decreases asymptotically to a certain limit. Based on the model the variability in tremor frequency in various experimental situations can be explained satisfactorily as a change in the loop-gain ratio.
バイオメカニズム学会の論文
1984-04-25

2反射ループ理論による手の生理的振戦のシミュレーション(1部ヒトのバイオメカニクス)

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2反射ループ理論による手の生理的振戦のシミュレーション(1部 ヒトのバイオメカニクス)

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2反射ループ理論による手の生理的振戦のシミュレーション(1部ヒトのバイオメカニクス)