Pattern of Recurrent Conditioning of Spinal Reflexes

Abstract

VARIOUS functions have been suggested for the recurrent conditioning described by Renshaw¹. Consonant with his view that the conditioning is “not obviously related to reciprocal innervation”¹, others have considered the widespread inhibitory action to serve a “generalized suppressor function”²; or to stabilize the impulse output in the stretch reflex at a slow rate³. As recurrent inhibition is prominent between the nuclei of two heads of a muscle or of two parts of a muscle group, it has been thought to help in the localization of stretch reflexes⁴. Following the finding that recurrent facilitation is evoked by activity of the cholinergic motor axon collaterals⁵, as is recurrent inhibition², the distribution of these two actions has been re-examined. Contrary to some previous descriptions, it now appears that the distribution of recurrent conditioning displays an integrated pattern which is in some respects related to reciprocal innervation.