It is well documented that variability in motor performance decreases with practice. Yet, the neural and computational mechanisms that underlie this decline, particularly during long-term practice, are only little understood. Decreasing variability is frequently examined in terms of error corrections from one trial to the next. However, the ubiquitous noise from all levels of the sensorimotor system is also a significant contributor to overt variability. While neuromotor noise is typically assumed and modeled as immune to practice, the current study challenged this notion. We investigated the long-term practice of a novel motor skill to test if neuromotor noise is attenuated, specifically when aided by reward. Results showed that both reward and self-guided practice over 11 days improved behavior by decreasing the noise processes, rather than effective error corrections. When increasing the challenge for obtaining reward, subjects reduced noise even further. Importantly, when task demands were relaxed again, this reduced level of noise persisted for five days. A stochastic learning model replicated both the attenuation and persistence of noise by scaling the noise amplitude as a function of reward. More insight into variability and intrinsic noise and its malleability has implications for training and rehabilitation interventions.
- motor learning
- skill acquisition
- neuromotor noise
- Copyright © 2016, Journal of Neurophysiology