Meeting Abstract

S7-1.2.2  Jan. 6  Obstacle avoidance during walking MCVEA, DA*; PEARSON, KG; University of Alberta; University of Alberta dmcvea@ualberta.ca

Two basic features of animal locomotion are 1) avoidance of obstacles that either impede progress or endanger the animal, and 2) withdrawal responses from obstacles that unexpectedly contact the animal. In walking mammals, the former depends primarily on visual information, while the latter depends on sensory information from the receptors in the skin. A major goal of the research program in our laboratory is to understand the neurobiology of these two aspects of obstacle avoidance in walking cats. One project is to establish the mechanisms that allow cats step precisely over visible obstacles. In this project we have focused on the role of short-term working memory in guiding the movements of the hind legs. Our results show that the hind legs are guided by a very long-lasting and precise memory of the position and size of the object, and that the movement of the forelegs over the obstacle is crucial for establishing this memory. Another major project in our laboratory has been to understand how an animal changes its stepping movements in response to persistent cutaneous stimulation of a hind leg. We have found that a relatively small number of cutaneous stimuli result in very long-lasting changes to the walking pattern. Interestingly, these changes are only expressed in the context in which the animal experienced the stimuli. Cortical areas of the brain play an important role in establishing this plasticity, as decerebrate cats show no long-term changes to stepping with the same stimuli. Our results to date clearly demonstrate that a full understanding of the neurobiology of walking will require knowledge about how the location of objects relative to the body and the environmental context in which the animal is walking are represented in neuronal networks in the brain, and how this information influences the basic neuronal networks in the spinal cord.