Efficient Coding in Motor Planning

A paramount challenge for the brain is to precisely model the world and control behavior within the confines of limited encoding capacities. Efficient coding theory posits a unified framework for understanding how neural systems enhance encoding accuracy by tuning to environmental statistics. While this theory has been thoroughly explored within the perceptual realm, it is less clear how efficient coding applies to the motor system. Here, we probe the core principles of efficient coding theory through center-out reaching tasks. Our results reveal novel sequential effects in motor planning. Specifically, current movements are biased in a direction opposite to recent movements, and movement variance increases with the angular divergence between successive actions. These effects are modulated by the variability within the motor system: a larger repulsive bias is observed when movements are performed with the nondominant hand compared to the dominant hand, and in individuals exhibiting higher motor variance compared to those with lower variance. These behavioral findings align with the predictions of an efficient coding model, suggesting that the motor system rapidly adapts to the context to enhance accuracy in motor planning.