Directional errors of movement and their correction in a discrete tracking task

Many studies have shown that subjects can correct their own errors of movement more quickly than they can react to external stimuli. In the control of movements, three general categories of feedback have been defined as follows: (a) knowledge of results, primarily visually mediated, (b) proprioceptive or kinesthetic, such as from muscle spindles and joint receptors, and (c) corollary discharge or efference copy within the central nervous system. Experiments were conducted on eight normal human subjects to study the effects of these feedbacks on simple RT, choice RT, and error correction time. The movement used was plantarflexion and dorsiflexion of the ankle joint. The feedback loops were modified (a) by inverting the visual display to alter the subject's perception of results and (b) by applying a 100-Hz vibration simultaneously to both flexor and extensor muscles of the ankle joint. Central processing was altered by giving the subjects moderated doses of alcohol (blood-alcohol concentration levels of up to.10%). Vibration and alcohol increased both simple and choice RT but not the error correction time. These data reinforce the concept that there is a central pathway which can mediate error correcting responses.