When practice leads to co-articulation: The evolution of geometrically defined movement primitives

Ronen Sosnik, Bjoern Hauptmann, Avi Karni, Tamar Flash

Research output: Contribution to journalArticlepeer-review


The skilled generation of motor sequences involves the appropriate choice, ordering and timing of a sequence of simple, stereotyped movement elements. Nevertheless, a given movement element within a well-rehearsed sequence can be modified through interaction with its neighboring elements (co-articulation). We show that extensive training on a sequence of planar hand trajectories passing through several targets resulted in the co-articulation of movement components, and in the formation of new movement elements (primitives). Reduction in movement duration was accompanied by the gradual replacement of straight trajectories by longer curved ones, the latter affording the maximization of movement smoothness. Surprisingly, the curved trajectories were generated even when new target configurations were introduced, i.e., when target distances were scaled, movement direction reversed or when different start and end positions were used, indicating the acquisition of geometrically defined movement elements. However, the new trajectories were not shared by the untrained hand. Altogether, our results suggest that novel movement elements can be acquired through extensive training in adults.

Original languageEnglish
Pages (from-to)422-438
Number of pages17
JournalExperimental Brain Research
Issue number4
StatePublished - Jun 2004

Bibliographical note

Funding Information:
Acknowledgements We sincerely thank Drs. Magnus Richardson and Felix Polyakov for many helpful discussions and for assistance in modeling the data. This work was supported in part by the Einhorn-Dominic Foundation and by the Morros laboratory.


  • Co-articulation
  • Motor control
  • Movement primitives
  • Sequence learning

ASJC Scopus subject areas

  • General Neuroscience


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