Evidence of static and dynamic fusimotor actions on the spindle response to sinusoidal stretch during locomotor activity in the cat.

Abstract

In the decorticated cat the spontaneous locomotor activity in an extensor muscle of the hind limb induces, in the absence of contraction of this muscle, a rhythmic increase in the response of primary fusorial fibers to sinusoidal stretch. This can be interpreted partly as an increase in the dynamic fusimotor activity linked in normal conditions with motor command. Such an action in a flexor muscle is sometimes seen, but more often, it is masked (or replaced) by a static fusimotor effect which can, depending upon its intensity, increase or decrease responses to stretch of the primary fusorial endings.