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This Article Full Text Full Text (PDF) All Versions of this Article: 94/2/1459    most recent 00685.2004v2 Alert me when this article is cited 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 (7) Citing Articles via Google Scholar Google Scholar Articles by Yekutieli, Y. Articles by Flash, T. Search for Related Content PubMed PubMed Citation Articles by Yekutieli, Y. Articles by Flash, T.

Dynamic Model of the Octopus Arm. II. Control of Reaching Movements

¹Department of Neurobiology and ²Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem; and ³Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel

Submitted 6 July 2004; accepted in final form 2 March 2005

The dynamic model of the octopus arm described in the first paper of this 2-part series was used here to investigate the neural strategies used for controlling the reaching movements of the octopus arm. These are stereotypical extension movements used to reach toward an object. In the dynamic model, sending a simple propagating neural activation signal to contract all muscles along the arm produced an arm extension with kinematic properties similar to those of natural movements. Control of only 2 parameters fully specified the extension movement: the amplitude of the activation signal (leading to the generation of muscle force) and the activation traveling time (the time the activation wave takes to travel along the arm). We found that the same kinematics could be achieved by applying activation signals with different activation amplitudes all exceeding some minimal level. This suggests that the octopus arm could use minimal amplitudes of activation to generate the minimal muscle forces required for the production of the desired kinematics. Larger-amplitude signals would generate larger forces that increase the arm’s stability against perturbations without changing the kinematic characteristics. The robustness of this phenomenon was demonstrated by examining activation signals with either a constant or a bell-shaped velocity profile. Our modeling suggests that the octopus arm biomechanics may allow independent control of kinematics and resistance to perturbation during arm extension movements.

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