Simulations of Motor Adaptation with the Multi-Rate Model Explain a Variety of Previously Reported Results, Including Rapid Unlearning and Rapid Downscaling

<div><p>(A–C) Anterograde interference.</p> <p>(D–F) Rapid unlearning.</p> <p>(G–I) Rapid downscaling.</p> <p>First column (A, D, and G): experiment paradigms. Second column (B, E, and H): Raw simulation results. Blue: initial adaptation. Red, green, and cyan: secondary adaptation after 30, 60, or 120 trials of the initial adaptation, respectively. Third column (C, F, and I): Comparison of adaptation rates for initial and secondary adaptations. Here the learning curves have been shifted so that they all begin at zero and scaled so that the desired performance level is one. In the anterograde interference paradigm (A–C), the multi-rate model predicts that learning the opposite force field proceeds with a slower time constant than initial learning; furthermore, this time constant gets even slower when number of trials in the initial learning block is increased. The multi-rate model predicts that unlearning proceeds with a faster time constant than initial learning (E–F) and the time constant for downscaling is faster still (H–I); however, the time constant for unlearning or downscaling returns to baseline when the number of trials in the initial learning block is increased. In summary, the multi-rate model simultaneously explains the effects of anterograde interference, rapid unlearning, and rapid downscaling. Furthermore this model predicts that anterograde interference will get stronger as the length of the initial adaptation period increases, but that rapid unlearning and rapid downscaling will get weaker as the length of the initial adaptation period increases.</p>