Motor control

Motor control is the systematic regulation of movement in organisms that possess a nervous system. Motor control includes movement functions which can be attributed to reflex,. Motor control as a field of study is primarily a sub-discipline of psychology or neurology. Motor control is the systematic regulation of movement in organisms that possess a nervous system. Motor control includes movement functions which can be attributed to reflex,. Motor control as a field of study is primarily a sub-discipline of psychology or neurology. Recent psychological theories of motor control present it as a process by which humans and animals use their brain/cognition to activate and coordinate the muscles and limbs involved in the performance of a motor skill. From this mixed psychological perspective, motor control is fundamentally the integration of sensory information, both about the world and the current state of the body, to determine the appropriate set of muscle forces and joint activations to generate some desired movement or action. This process requires cooperative interaction between the central nervous system and the musculoskeletal system, and is thus a problem of information processing, coordination, mechanics, physics, and cognition. Successful motor control is crucial to interacting with the world, not only determining action capabilities, but regulating balance and stability as well. The organization and production of movement is a complex problem, so the study of motor control has been approached from a wide range of disciplines, including psychology, cognitive science, biomechanics and neuroscience. While the modern study of motor control is an increasingly interdisciplinary field, research questions have historically been defined as either physiological or psychological, depending on whether the focus is on physical and biological properties, or organizational and structural rules. Areas of study related to motor control are motor coordination, motor learning, signal processing, and perceptual control theory. The process of becoming aware of a sensory stimuli and using that information to influence an action occurs in stages, and reaction time of simple tasks can be used to reveal information about these stages. Reaction time refers to the period of time between when the stimulus is presented, and the end of the response. Movement time is the time it takes to complete the movement. Some of the first reaction time experiments were carried out by Franciscus Donders, who used the difference in response times to a simple reaction task and a choice reaction task to determine the length of time needed to process the stimuli and choose the correct response. While this approach is ultimately flawed, it gave rise to the idea that reaction time was made up of a stimulus identification, followed by a response selection, and then the correct movement was carried out. Further research has provided evidence that these stages do exist, but that the response selection period of any reaction time increases as the number of available choices grows, a relationship known as Hick's law. The classical definition of a closed loop system for human movement comes from Jack A. Adams (1971) : „ A closed loop system has feedback, error detection and error correction as key elements. There is a reference that specifies the desired value for the system, and the output of the system is fed back and compared to the reference for error detection and, if necessary corrected..... A closed loop system is self regulating by compensating for deviating from the reference.” Most movements that are carried out during day-to-day activity are formed using a continual process of accessing sensory information and using it to more accurately continue the motion. This type of motor control is called feedback control, as it relies on sensory feedback to control movements. Feedback control is a situated form of motor control, relying on sensory information about performance and specific sensory input from the environment in which the movement is carried out. This sensory input, while processed, does not necessarily cause conscious awareness of the action. Closed loop control is a feedback based mechanism of motor control, where any act on the environment creates some sort of change that affects future performance through feedback. Closed loop motor control is best suited to continuously controlled actions, but does not work quickly enough for ballistic actions. Ballistic actions are actions that continue to the end without thinking about it, even when they no longer are appropriate.Because feedback control relies on sensory information, it is as slow as sensory processing. These movements are subject to a speed/accuracy trade-off, because sensory processing is being used to control the movement, the faster the movement is carried out, the less accurate it becomes. The classical definition from Jack .A. Adams is: “An open loop system has no feedback or mechanisms for error regulation. The input events for a system exert their influence, the system effects its transformation on the input and the system has an output...... A traffic light with fixed timing snarls traffic when the load is heavy and impedes the flow when the traffic is light. The system has no compensatory capability.” Some movements, however, occur too quickly to integrate sensory information, and instead must rely on feed forward control. Open loop control is a feed forward form of motor control, and is used to control rapid, ballistic movements that end before any sensory information can be processed. To best study this type of control, most research focuses on deafferentation studies, often involving cats or monkeys whose sensory nerves have been disconnected from their spinal cords. Monkeys who lost all sensory information from their arms resumed normal behavior after recovering from the deafferentation procedure. Most skills were relearned, but fine motor control became very difficult. It has been shown that the open loop control can be adapted to different disease conditions and can therefore be used to extract signatures of different motor disorders by varying the cost functional governing the system. A core motor control issue is coordinating the various components of the motor system to act in unison to produce movement. The motor system is highly complex, composed of many interacting parts at many different organizational levels