Motor control schemes in the cerebellum and motor cortices

Introduction: The intricacies and complexities of the primate motor control system are simply mind-boggling. This is evident by looking at the magnitude of theories that are continuously being published, refined, and outright rejected on almost a weekly basis. Many times the problem comes down to the limited scope of the investigation. The primate motor control system is so incredibly multi-dimensional and non-linear that any engineer would tremble at the thought of characterizing such a juggernaut. But, no matter how complex the controller may be, it can be broken down into functional feedforward and feedback sensorimotor transformations. Almost any theory on motor control will define what roles one or both of these control schemes play [1-15]. A feedback control scheme uses state-related information (e.g. afferent signals) in the computation of the control signal. Feedforward control relies on an intrinsic model of the plant in its estimate of the control signal. While most researchers would attest to the fact that biological motor control systems inevitably take advantage of both control schemes, few provide any convincing physiological evidence on the sources of them in the brain. Since it is widely accepted that much of motor control in primates is distributed throughout the cerebellum and motor cortices of the cerebrum (e.g. primary, supplemental, premotor, and posterior parietal), the primary goal of this proposal is to answer the following: What control schemes are used in the cerebellum and motor cortices? The approach we will initially take is to classify each of the regions as primarily using feedback (using state information) or feedforward (prediction using intrinsic model). In route to addressing the proposal's primary goal, we will also put forward two related secondary goals that can be pursued in parallel to the primary goal and without adding too much complexity to the project. The secondary goals answer the following questions: 1) What are the relative responsibilities of the cerebellum and motor cortices in primate motor control? ; and 2) How is state information encoded in these two brain structures? (As an informal goal we'll either confirm or disprove the proposed control architecture illustrated in figure 1; the letters attached to each block will be used to refer to that block.). These three questions are motivated by many active issues in the discipline of motor control. Studies on BMI typically record from the cerebrum (motor cortices) and develop control laws based on those correlations with motor activity. …