Modulation of cutaneous reflexes in hindlimb muscles during locomotion in the freely walking rat: A model for studying cerebellar involvement in the adaptive control of reflexes during rhythmic movements

Abstract

This study aims to demonstrate stepphase-dependent modulation in the gain of cutaneously triggered reflexes in the freely locomoting rat. Electromyographic recordings of biceps femoris (mainly involved in knee flexion) and gastrocnemius (mainly involved in ankle extension) muscles were continuously monitored during locomotion and cutaneous reflexes were induced by subcutaneously placed stimulation electrodes in the lateral malleolal region. The results show that the reflex responses in both muscles during locomotion were generally reduced compared to reflexes induces in rest. For the biceps femoris reduction of reflex gain was highest during the stance phase whereas for the gastrocnemius the period of highest depression was found during the swing phase. We conclude that stepphase-dependent modulation of peripheral reflexes can be measured in freely locomoting rats and generally concur with previous studies in cat and man that this type of modulation may be functionally important for maintaining and adjusting gait. Moreover, although the mechanism of inducing and maintaining this modulation is not fully known, it is now open to experimental investigation in rodents.