Causal Role of Motor Preparation during Error-Driven Learning

Current theories suggest that an error-driven learning process updates trial-by-trial to facilitate motor adaptation. How this process interacts with motor cortical preparatory activity—which current models suggest plays a critical role in movement initiation—remains unknown. Here, we evaluated the role of motor preparation during visuomotor adaptation. We found that preparation time was inversely correlated to variance of errors on current trials and mean error on subsequent trials. We also found causal evidence that intracortical microstimulation during motor preparation was sufficient to disrupt learning. Surprisingly, stimulation did not affect current trials, but instead disrupted the update computation of a learning process, thereby affecting subsequent trials. This is consistent with a Bayesian estimation framework where the motor system reduces its learning rate by virtue of lowering error sensitivity when faced with uncertainty. This interaction between motor preparation and the error-driven learning system may facilitate new probes into mechanisms underlying trial-by-trial adaptation. •Longer motor preparation times yield greater learning•Motor preparation plays a causal role in visuomotor adaptation•Motor cortical preparatory state engages with a learning process•Disrupting preparatory states likely reduces learning by lowering error sensitivity Vyas et al. use microstimulation to establish a causal relationship between motor cortical preparatory activity and learning. Disrupting preparatory activity affects subsequent but not stimulated trials. Preparatory activity plays a critical role in trial-by-trial update computations of a learning process.