Motor systems - Editorial overview

For many years research on the sensory systems, and the visual system in particular, dominated the filed of neuroscience. Although research on the motor system provided tremendous insight as sophisticated as that in the sensory systems, these results seemed much more difficult to relate to other fields of neurophysiology and, in particular, to the rapidly developing cognitive neurosciences. Motor system research was firmly in the domain of the specialists and clinical neurologists investigating the devastating effects of motor system damage. This is certainly not the case today. Following the seminal work of Mountcastle [1] and Hyvarinen [2], it became evident that the cortical areas involved in motor control are not only the frontal agranular areas - the traditional motor region - but also the parietal cortical areas. Thus, the notion of association parietal cortex changed. The view that the parietal cortex was the place where different sensory modalities were 'put together' was substituted by the notion that the parietal cortex is the place where different modalities are integrated with action representations. At the same time new and more sophisticated Computational models provided the tools that enabled a deeper understanding of how actions are planned and performed. Furthermore, these same models provided fundamental tools for understanding cognitive functions. As a consequence, the Studies of the motor system acquired a much broader scope and motor systems became a crucial system for cognition. The wide range of topics selected for the present issue illustrates the advances that have recently been made in understanding various aspects of cortical motor organization, in addition to that of cerebellum and basal ganglia. Most of the reviews concern experiments on the motor system of humans and monkeys, one is devoted to motor organization in invertebrates.'Small brains' are an important tool for understanding the complexity of motor organization in anatomically and functionally complex motor systems.