Learning versus learned: Flexible control processes when reaching with altered visual feedback of the hand's position


We examined control processes underlying reaches when participants were first introduced to a visuomotor distortion (Experiment 1) and then following visuomotor adaptation (Experiment 2). All participants completed 150 reach training trials when (1) a cursor accurately represented their hand motion (i.e., aligned cursor) and (2) a cursor was rotated 45 degrees clockwise relative to their hand motion (i.e., rotated cursor). In Experiment 1, participants (n = 16) received either continuous visual feedback or terminal visual feedback regarding movement endpoint during reach training. Analyses revealed that participants were able to demonstrate similar outcomes (i.e., movement time and endpoint errors) regardless of visual or cursor feedback, but demonstrated more offline control (i.e., took more time and were less consistent in initiating their movements) when reaching with a rotated cursor compared to an aligned cursor, even at the end of training. In attempt to promote online corrective processes, participants (n = 16) in Experiment 2 first completed the training trials with continuous visual feedback and then completed an additional 45 reaches under (1) slow MT (800-1000 ms) and (2) fast MT constraints (400-500 ms). Results showed a shift to online control (i.e., greater endpoint accuracy) when reaching with an aligned and rotated cursor, when sufficient time was provided (i.e., Slow MT). Together, these experiments demonstrate a flexibility in control processes underlying reaches with rotated visual feedback of the hand, in that reaches first engage offline control processes during learning, and then shift to online corrective processes once the visual distortion is learned.

Acknowledgments: Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC); awarded to the last author.