A technique for measuring the mechanical actions of heterogenic (intermuscular) reflexes in the decerebrate cat.

Two muscle pullers were used to study the natural mechanical actions of autogenic reflexes, which arise from muscle receptors and feed back to the muscle of origin, and heterogenic reflexes, which feed back to muscles other than the muscle of origin. In the study reported here, the reflexes associated with muscles which act about the ankle joint of the decerebrate cat were investigated. Actions of autogenic pathways were measured by imposing length changes on the muscle and recording the resulting changes in force and EMG (electromyogram). Actions of heterogenic reflexes for pairs of muscles were measured by imposing appropriate combinations of length changes on the muscle of origin and on the muscle receiving the heterogenic reflex. In some cases, length changes were applied in such a way as to mimic normal mechanical coupling to evaluate the physiological importance of the reflexes, while in other cases the tests departed from normal coupling to address questions about mechanisms of reflex action. It was found that several pairs of muscles could be studied in a single experiment so that supraspinal influences on the pattern of spinal reflex connectivity can be conveniently evaluated.