The primary motor cortex is critical for the retention of implicit sensorimotor adaptation

Sensorimotor adaptation, or adaptation of movements to external perturbations, is thought to involve the primary motor cortex (M1). In addition to implicit error-driven remapping, explicit re-aiming strategies also contribute to sensorimotor adaptation. However, no studies to date have examined the role of M1 in implicit learning in isolation from explicit strategies. Because the application of explicit strategies requires time, it is possible to emphasise implicit learning by controlling the time available to prepare movement. Here, we examined the role of M1’s role in implicit adaptation to rotated visual feedback whilst suppressing the use of explicit re-aiming strategies by limiting movement preparation times to less than 350ms. Perturbing M1 activity via single-pulse TMS during adaptation to a 30 ° rotation of visual feedback did not alter the rate or extent of error compensation, but elicited poorer retention in post-adaptation trials with no perturbation. This work shows that M1 is critical in the retention of new visuomotor maps as a result of implicit adaptation to a perturbation in sensory feedback when strategic error correction processes are suppressed. Highlights Adaptation of movements to perturbations occurs through explicit and implicit processes. Here, explicit strategies were suppressed by shortening movement preparation time. Perturbing motor cortex (M1) with TMS selectively impaired retention but not acquisition of sensorimotor adaptation. M1 plays a crucial role in retention of sensorimotor adaptation obtained via implicit learning.