Meeting Abstract

S7-1.2.1  Jan. 6  Short- and long-term adaptation of the motor pattern for walking PEARSON, K.G.*; MCVEA, D.A.; University of Alberta, Edmonton; University of Alberta, Edmonton

An obvious feature of animal locomotion is the ability to rapidly change motor patterns to adapt movements to a changing environment. Less obvious is the capacity to modify motor patterns to compensate for changes in body mechanics and to persistent changes in the environment. In this presentation we will describe recent investigations in our laboratory aimed at establishing the neuronal mechanisms underlying these forms of adaptation in the walking system of cat. The short-term adaptations we have examined are responses to unexpected changes in ground support and walking up and down steps of different slopes. In both situations significant changes occur in the level of activity in leg extensor muscles that function to compensate for changes in loading of the legs. Changes in extensor activity depend in part on the existence of positive feedback pathways from force-sensitive afferents to extensor motoneurons. The long-term adaptations we have examined include changes in response to weakening ankle extensor muscles and modifications in the swing phase of the hind legs to avoid an obstacle that contacts a hind paw during the swing phase. These perturbations result in persistent increases in the level of activity in ankle extensor and knee flexor muscles, respectively, with the latter depending on the environmental context in which the animal received the stimuli.