Posture and movements are out, only physical means of interacting with the environment. As we express Our thoughts and emotions through posture and movements, they indicate our will or intentions. Locomotion is representative of purposeful goal-directed behaviors that are initiated by signals arising from either volitional processing in the cerebral cortex or emotional processing in the limbic system. Regardless of whether the locomotion is volitional or emotional, it is accompanied by automatically controlled movement processes such as the adjustment of postural muscle tone and rhythmic limb movements that are unconsciously executed. Sensori-motor integration at the level of the brainstem and spinal cord plays major roles in this automatic control. Signals processed in the basal ganglia and the cerebellum act on the cerebral cortex, the limbic system and the brainstem so that locomotor behaviors are appropriately and precisely regulated depending on the behavioral context. The purpose of this review is to describe how purposeful locomotor behaviors are initiated, executed and regulated so as to enable locomotive subjects to interact with and adapt to the environment. (C) Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2008
