Grant: Operating Grant

Locomotion is the result of the combined activity of multiple structures at different levels in the nervous system. Neural circuits in the spinal cord produce the basic rhythmical activity of locomotion while structures in the brain with spinal projections modify this activity to the goals of the animal. In most situations, visual information is critical for modifying locomotion and is used to plan anticipatory modifications of gait to avoid an object or to direct the subject towards it. These functions, although performed seamlessly by all sighted, terrestrial mammals, require extensive processing of the visual information in order to plan and execute the appropriate modification of the locomotor pattern. While an emphasis is frequently placed on the cortical circuits involved in visuomotor planning, there is abundant evidence to suggest that subcortical structures, and especially the basal ganglia, are also critically involved in these activities. Patients with Parkinson's disease (a basal ganglia disorder), for example, show characteristic deficits in their walking, including a slow, shuffling gait and, in more advanced stages of the disease, a condition known as freezing of gait, during which they are unable to initiate the next step. This is particularly evident at gait initiation or in more difficult conditions requiring visual control of locomotion, e.g doorways and sharp turns. While the clinical symptoms of these deficits are well described we have almost no information of the neural activity of the basal ganglia during locomotion, especially when obstructed. The current research programme is designed to determine how the basal ganglia contribute to different aspects of walking, such as its speed, force and modification in response to visually-identified obstruction. It is expected that a clear understanding of the neuronal mechanisms underlying the basal ganglia control of locomotion will help to modify treatment strategies and interventions in patients.