Posture, gait and body schema in relation to the basal ganglia movement control

I review substrates for the execution of normal gait and to understand pathophysiological mechanisms of gait failure in basal ganglia dysfunctions. In Parkinson's disease, volitional and emotional expressions of movement processes are seriously affected in addition to the disturbance of automatic movement processes, such as adjustment of postural muscle tone and rhythmic limb movements during walking. These patients also suffer from muscle tone rigidity and postural instability, which may also cause reduced walking capabilities. Clinical and neurophysiological studies have suggested the importance of basal ganglia connections with the cerebral cortex and limbic system in the expression of volitional and emotional behaviors, respectively. On the other hand, basal ganglia output toward the brainstem (basal ganglia-brainstem system) can be critically involved in the integrative control of muscle tone and locomotion. Recently emphasis has been placed on the importance of body schema, or internal postural model, which is generated at parietal cortex by integrating multimodal (proprioceptive, visual, auditory and vestibular) sensory inputs. The body schema can be required for motor programming of intentionally controlled precise movements and anticipatory postural control. Based on these considerations I provide a hypothetical model for understanding the role of the basal ganglia in the control of volitional and automatic aspects of movements and pathophysiological mechanisms of basal ganglia motor disorders.