A memory of errors in sensorimotor learning

Abstract

The current view of motor learning suggests that when we revisit a task, the brain recalls the motor commands it previously learned. In this view, motor memory is a memory of motor commands, acquired through trial-and-error and reinforcement. Here we show that the brain controls how much it is willing to learn from the current error through a principled mechanism that depends on the history of past errors. This suggests that the brain stores a previously unknown form of memory, a memory of errors. A mathematical formulation of this idea provides insights into a host of puzzling experimental data, including savings and meta-learning, demonstrating that when we are better at a motor task, it is partly because the brain recognizes the errors it experienced before.

Formation of a long-term memory for visuomotor adaptation following only a few trials of practice

“…The sensitivity-to-error model proposed by Herzfeld et al (2014) cannot account for all of our results, however. In particular, it predicts that adaptation rate upon reexposure to a given perturbation will steadily increase as the duration of the initial exposure to the perturbation increases, even after one reaches asymptote.…”

“…A recent study suggested that savings may not be due to recall of prior actions but rather might be due to an underlying sensory-error-driven learning process increasing its sensitivity to previously experienced errors (Herzfeld et al 2014). The authors of that study showed that experiencing a particular error at one time leads to a durable change in response to the same or similar errors in the future.…”

“…Alternatively, subjects may form a memory for action (Huang et al 2011;Xivry and Lefévre 2015), as opposed to a memory for an aiming direction (Taylor et al 2014), or a memory for the perturbation (Herzfeld et al 2014). We have previously suggested that this may occur through an implicit reinforcement learning mechanism that is established through experience (Huang et al 2011).…”

“…This "single-trial learning rate" was defined as the change in reach direction from the first to the second trial of a rotation. The use of a single trial to determine an estimate for learning rate has been employed by others (Marko et al 2012;Semrau et al 2012;Gonzalez Castro et al 2014;Herzfeld et al 2014). To formally test this difference, a paired t-test was conducted for each group comparing the single-trial learning rate between the first and second rotation exposures within each subject.…”

“…We have previously argued that repetition of an action during the initial rotation exposure is necessary to recall that action during a subsequent exposure (Huang et al 2011). A second theory has proposed that savings comes about not through recall but through an increase in the sensitivity of the same error-driven process that is present during initial adaptation (Braun et al 2009;Kobak and Mehring 2012;Yousif and Diedrichsen 2012;Gonzalez Castro et al 2014;Herzfeld et al 2014). These theories also tend to assume that savings increases with initial exposure to a perturbation.…”