Adaptation to suppression of visual information during catching.

We address the problem of whether and how adaptation to suppression of visual information occurs in catching behavior. To this end, subjects were provided with advance information about the height of fall and the mass of a ball and an auditory cue signaled the time of release. Adaptation did occur, as indicated by the unimpaired ability to catch the ball without vision; however, it involved a major reorganization of the muscle responses. The subjects were unable to produce anticipatory activity consistently, but preset the responses elicited by the impact. These responses were more complex and prolonged than those observed in the control experiments (with vision). In particular, medium- and long-latency responses were much larger, and the changes in elbow, wrist, and metacarpophalangeal angles following impact were more oscillatory than in the control. The general pattern of the EMG responses switched from that characteristic of catching with vision to that characteristic of catching without vision from the first trial of each experiment. However, the responses produced without vision were calibrated adaptively in the course of an experiment. In fact, the limb oscillations induced by the impact were significantly larger in the first trial than in the following trials. This seems to suggest that the parameters of the responses are adjusted based on an internal model of the dynamic interaction between the falling ball and the limb. This model is initially constructed from a priori knowledge on impact parameters and is subsequently updated on the basis of the kinesthetic and cutaneous information obtained during the first trial.