title: Delayed feedback during sensorimotor learning selectively disrupts adaptation but not strategy use.
abstract: In sensorimotor adaptation tasks, feedback delays can cause significant reductions in the rate of learning. This constraint is puzzling given that many skilled behaviors have inherently long delays (e.g., hitting a golf ball). One difference in these task domains is that adaptation is primarily driven by error-based feedback, whereas skilled performance may also rely to a large extent on outcome-based feedback. This difference suggests that error- and outcome-based feedback may engage different learning processes, and these processes may be associated with different temporal constraints. We tested this hypothesis in a visuomotor adaptation task. Error feedback was indicated by the terminal position of a cursor, while outcome feedback was indicated by points. In separate groups of participants, the two feedback signals were presented immediately at the end of the movement, after a delay, or with just the error feedback delayed. Participants learned to counter the rotation in a similar manner regardless of feedback delay. However, the aftereffect, an indicator of implicit motor adaptation, was attenuated with delayed error feedback, consistent with the hypothesis that a different learning process supports performance under delay. We tested this by employing a task that dissociates the contribution of explicit strategies and implicit adaptation. We find that explicit aiming strategies contribute to the majority of the learning curve, regardless of delay; however, implicit learning, measured over the course of learning and by aftereffects, was significantly attenuated with delayed error-based feedback. These experiments offer new insight into the temporal constraints associated with different motor learning processes.
authors.affiliation: Duke Institute for Brain Sciences, Duke University, Durham, North Carolina;
authors.forename: Samuel N
authors.initials: SN
authors.lastname: Brudner
authors.affiliation: Department of Psychology, Princeton University, Princeton, New Jersey;
authors.forename: Nikhit
authors.initials: N
authors.lastname: Kethidi
authors.affiliation: Department of Psychology, Princeton University, Princeton, New Jersey; Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey;
authors.forename: Damaris
authors.initials: D
authors.lastname: Graeupner
authors.affiliation: Department of Psychology, University of California, Berkeley, California; and Helen Wills Neuroscience Institute, University of California, Berkeley, California.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Ivry
authors.affiliation: Department of Psychology, Princeton University, Princeton, New Jersey; Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey; jordanat@princeton.edu.
authors.forename: Jordan A
authors.identifier: http://orcid.org/0000-0001-9300-1229
authors.initials: JA
authors.lastname: Taylor
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology; D025461:Feedback, Physiological; D005260:Female; D006801:Humans; D007858:Learning; D008297:Male; D011597:Psychomotor Performance; D014796:Visual Perception
keywords: forward model; internal model; motor adaptation; motor learning; reinforcement learning