QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

The Journal of Neuroscience, August 29, 2007, 27(35):9354-9368; doi:10.1523/JNEUROSCI.1110-06.2007

This Article Full Text Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Liu, D. Articles by Todorov, E. Search for Related Content PubMed PubMed Citation Articles by Liu, D. Articles by Todorov, E.

 Previous Article  |  Next Article 

Behavioral/Systems/Cognitive
Evidence for the Flexible Sensorimotor Strategies Predicted by Optimal Feedback Control

Dan Liu and Emanuel Todorov

Department of Cognitive Science, University of California, San Diego, La Jolla, California 92093-0515

Correspondence should be addressed to Emanuel Todorov at the above address. Email: todorov{at}cogsci.ucsd.edu

Everyday movements pursue diverse and often conflicting mixtures of task goals, requiring sensorimotor strategies customized for the task at hand. Such customization is mostly ignored by traditional theories emphasizing movement geometry and servo control. In contrast, the relationship between the task and the strategy most suitable for accomplishing it lies at the core of our optimal feedback control theory of coordination. Here, we show that the predicted sensitivity to task goals affords natural explanations to a number of novel psychophysical findings. Our point of departure is the little-known fact that corrections for target perturbations introduced late in a reaching movement are incomplete. We show that this is not simply attributable to lack of time, in contradiction with alternative models and, somewhat paradoxically, in agreement with our model. Analysis of optimal feedback gains reveals that the effect is partly attributable to a previously unknown trade-off between stability and accuracy. This yields a testable prediction: if stability requirements are decreased, then accuracy should increase. We confirm the prediction experimentally in three-dimensional obstacle avoidance and interception tasks in which subjects hit a robotic target with programmable impedance. In additional agreement with the theory, we find that subjects do not rely on rigid control strategies but instead exploit every opportunity for increased performance. The modeling methodology needed to capture this extra flexibility is more general than the linear-quadratic methods we used previously. The results suggest that the remarkable flexibility of motor behavior arises from sensorimotor control laws optimized for composite cost functions.

Key words: arm movement; optimal feedback control; composite cost; obstacle avoidance; stability–accuracy trade-off; behavioral flexibility

---

Received March 15, 2006; revised June 4, 2007; accepted July 9, 2007.

Correspondence should be addressed to Emanuel Todorov at the above address. Email: todorov{at}cogsci.ucsd.edu

This article has been cited by other articles:

				S. H. Scott Inconvenient Truths about neural processing in primary motor cortex J. Physiol., March 1, 2008; 586(5): 1217 - 1224. [Abstract] [Full Text] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help