Learning feedback and feedforward control in a mirror-reversed visual environment

Abstract

When we learn a novel task, the motor system needs to acquire both feedforward and feedback control. Currently, little is known about how the learning of these two mechanisms relate to each other. In the present study, we tested whether feedforward and feedback control need to be learned separately, or whether they are learned as common mechanism when a new control policy is acquired. Participants were trained to reach to two lateral and one central target in an environment with mirror (left-right)-reversed visual feedback. One group was allowed to make online movement corrections, whereas the other group only received visual information after the end of the movement. Learning of feedforward control was assessed by measuring the accuracy of the initial movement direction to lateral targets. Feedback control was measured in the responses to sudden visual perturbations of the cursor when reaching to the central target. Although feedforward control improved in both groups, it was significantly better when online corrections were not allowed. In contrast, feedback control only adaptively changed in participants who received online feedback and remained unchanged in the group without online corrections. Our findings suggest that when a new control policy is acquired, feedforward and feedback control are learned separately, and that there may be a trade-off in learning between feedback and feedforward controllers.

Kinect V2 Performance Assessment in Daily-Life Gestures: Cohort Study on Healthy Subjects for a Reference Database for Automated Instrumental Evaluations on Neurological Patients

“…As a general remark, the sensibility of the proposed methodology (based on RM and HtMM) proved not to be particularly high on healthy subjects in distinguishing motor performances, while it is for neurological patients since it involves demanding gestures for impaired people. Such result was expected since daily-life, well known, and quite rapid gestures are performed mainly in feedforward control [ 65 ]. Thus, such gestures “belong” to the hard-coded, well-known set of mastered control abilities, as suggested by the Schema Theory of Motor Learning [ 16 ].…”

“…Furthermore, the methodology was designed considering the needs of neurological patients that, depending on the severity of their motor impairment, may consider RM and HtMM as highly complex and challenging to perform. For neurological patients, the RM and HtMM tasks include multijoint, coordinated movements against gravity, making them challenging enough to trigger the execution of feedback control, thus activating the process of motor learning and neuroplasticity typical of motor relearning [ 65 ].…”

Reward-based improvements in motor control are driven by multiple error-reducing mechanisms

“…This suggests that transcortical feedback gains can also be pre-computed before movement initiation to meet task demands. Finally, recent work shows that reward can indeed modulate visual feedback control in reaching (Carroll et al, 2019) at timescales of 170-220ms after movement onset, much faster than usually considered for this type of feedback control (Carroll et al, 2019; Kasuga et al, 2015). Despite this remarkable speed, considering our typical movement times, this would imply that feedback control is increased only after about half of the movement.…”

Feedback Adaptation to Unpredictable Force Fields in 250 ms

“…However, the observed feedback adaptation may not be functionally distinguishable from the standard adaptation: it enabled adjustments of motor output suitable to the experienced force field. Although feedback adaptation may be dissociable from feedforward adaptation (Yousif and Diedrichsen, 2012;Kasuga et al, 2015), and may not engage the same circuits, there is no reason a priori to dismiss it as a contributor to motor adaptation in general. A possible link between feedforward and feedback adaptation is that the online representation which is used to adapt the feedback response in a force field trial may be stored and used as a new prior for the next movement.…”