Quantification of spinal feedback gains

E. de Vlugt

ProGAMMA, Groningen, The Netherlands

Feedback loops are very important for the motion control behavior of human beings. Feedback loops consist of the Central Nervous System as controller, muscles as actuators, position, velocity and force sensors in the muscles and muscle tendons and the skeletal system as the linkage mechanism. During postural tasks the feedback system is very effective to counteract random perturbations that disturb away from the reference position. Robot manipulators are used for imposing force perturbations to the hand, thereby activating the closed loop feedback pathways. By recording signals inside the control loop, the dynamic behaviour of the components of the feedback loop can be estimated using advanced closed-loop system identification techniques. The control settings of the CNS, i.e. the so-called spinal reflex gains, can be estimated based on dynamic transfer functions. These reflex gains are rapidly modulated by healthy subjects, depending e.g. on the frequency content of the perturbation signal and the impedance of the environment. It can be shown that patients with neurological disorders have problems in modulating the reflexive feedback gains.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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