Roles of Feedback in the Stability of Multi-Finger Action
Open Access
- Author:
- Reschechtko, Sasha
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 01, 2018
- Committee Members:
- Mark Latash, Dissertation Advisor/Co-Advisor
Mark Latash, Committee Chair/Co-Chair
Robert L Sainburg, Committee Member
Jonas Rubenson, Committee Member
Andris Freivalds, Outside Member - Keywords:
- Motor Control
Multi-Finger Coordination
Sensory Feedback
Isometric Force Production
Uncontrolled Manifold Hypothesis
Referent Configuration Hypothesis
Synergy - Abstract:
- The ability to interact with the world in a consistent and predictable fashion is extremely important to our survival and wellbeing. The stability of our actions guaranteed by the healthy central nervous systems (CNS) is therefore a highly informative object of study. This dissertation investigates effects of various modalities of sensory feedback on the stability of isometric multi-finger action through a number of experiments which alter various combinations of sensory modalities. Stability of action is quantified using across-trials variance analysis techniques in the space of performance variables which subjects were instructed to maintain, which include (for different experiments) total force produced by the fingers, computed moment of force produced by the fingers, and relative contribution to total force for various fingers. In addition, stability of multi-finger action is quantified in the space of theoretical control variables relating to the coordinated spatial activation patterns of muscles which result in referent coordinates and apparent stiffnesses quantifiable for individual fingers and the hand as a whole. These latter variables are assessed both in terms of their effects on performance variables (descending synergies) as well as their situation in an assumed hierarchy of control (ascending synergies). Visual feedback on salient performance variables exerts a strong influence on the stability of action quantified at a task level, while manipulations of other feedback modalities are seen primarily when visual feedback is not available. Despite the effects of visual feedback at the task level, synergies in the space of control variables showed less modulation during visual manipulations and some ascending synergies even increased when visual feedback was removed. Together, these results reflect the high specificity of CNS in stabilizing certain aspects of task performance and suggest that such behaviors come about by altering inter-finger coordination without modifying certain basic aspects of the control of individual fingers.