On the origin of finger enslaving: Control with referent coordinates and effects of visual feedback

Valters Abolins, Alex Stremoukhov, Caroline Walter, Mark L. Latash (Corresponding Author)

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

When a person tries to press with a finger, other fingers of the hand produce force unintentionally. We explored this phenomenon of enslaving during unintentional force drifts in the course of continuous force production by pairs of fingers of a hand. Healthy subjects performed accurate force production tasks by finger pairs Index-Middle, Middle-Ring, and Ring-Little with continuous visual feedback on the combined force of the instructed (master) fingers or of the noninstructed (enslaved) fingers. The feedback scale was adjusted to ensure that the subjects did not know the difference between these two, randomly presented, conditions. Across all finger pairs, enslaved force showed a drift upward under feedback on the master finger force, and master force showed a drift downward under feedback on the enslaved finger force. The subjects were unaware of the force drifts, which could reach over 50% of the initial force magnitude over 15 s. Across all conditions, the index of enslaving increased by ~50% over the trial duration. The initial moment of force magnitude in pronation-supination was not a consistent predictor of the force drift magnitude. These results falsify the hypothesis that the counter-directional force drifts reflected drifts in the moment of force. They suggest that during continuous force production, enslaving increases with time, possibly due to the spread of excitation over cortical finger representations or other mechanisms, such as increased synchronization of firing of a-motoneurons innervating different compartments of extrinsic flexors. These changes in enslaving, interpreted at the level of control with referent coordinates for the fingers, can contribute to a variety of phenomena, including unintentional force drifts.

Original languageEnglish
Pages (from-to)1625-1636
Number of pages12
JournalJournal of Neurophysiology
Volume124
Issue number6
DOIs
Publication statusPublished - 30 Nov 2020
Externally publishedYes

Keywords*

  • Activation spread
  • Force drift
  • Moment of force
  • Referent coordinate

Field of Science*

  • 5.1 Psychology
  • 3.2 Clinical medicine
  • 3.1 Basic medicine

Publication Type*

  • 1.1. Scientific article indexed in Web of Science and/or Scopus database

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