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When Optimal Feedback Control Is Not Enough: Feedforward Strategies Are Required for Optimal Control with Active Sensing

Published version
Peer-reviewed

Change log

Authors

Yeo, S-H 
Franklin, DW 
Wolpert, DM 

Abstract

Movement planning is thought to be primarily determined by motor costs such as inaccuracy and effort. Solving for the optimal plan that minimizes these costs typically leads to specifying a time-varying feedback controller which both generates the movement and can optimally correct for errors that arise within a movement. However, the quality of the sensory feedback during a movement can depend substantially on the generated movement. We show that by incorporating such state-dependent sensory feedback, the optimal solution incorporates active sensing and is no longer a pure feedback process but includes a significant feedforward component. To examine whether people take into account such state-dependency in sensory feedback we asked people to make movements in which we controlled the reliability of sensory feedback. We made the visibility of the hand state-dependent, such that the visibility was proportional to the component of hand velocity in a particular direction. Subjects gradually adapted to such a sensory perturbation by making curved hand movements. In particular, they appeared to control the late visibility of the movement matching predictions of the optimal controller with state-dependent sensory noise. Our results show that trajectory planning is not only sensitive to motor costs but takes sensory costs into account and argues for optimal control of movement in which feedforward commands can play a significant role.

Description

Keywords

Adult, Biomechanical Phenomena, Computational Biology, Feedback, Sensory, Female, Hand, Humans, Male, Motor Activity, Psychomotor Performance, Young Adult

Journal Title

PLoS Computational Biology

Conference Name

Journal ISSN

1553-734X
1553-7358

Volume Title

12

Publisher

Public Library of Science
Sponsorship
Wellcome Trust (097803/Z/11/Z)
Wellcome Trust (Grant IDs: WT091547MA, WT097803MA), Royal Society (Noreen Murray Professorship in Neurobiology)