DISCRETE AND CYCLICAL FORCE PRODUCTION IN MULTI-FINGER PRESSING AND PREHENSION TASKS

Open Access
- Author:
- Srinivasan KariyaMaanikam, Varadhan
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 09, 2011
- Committee Members:
- Mark Latash, Dissertation Advisor/Co-Advisor
Mark Latash, Committee Chair/Co-Chair
Vladimir M Zatsiorsky, Committee Member
Robert L Sainburg, Committee Member
Joseph Paul Cusumano, Committee Member - Keywords:
- Discrete
Cyclic
Finger
Force
Pressing
Prehension - Abstract:
- Differences between discrete and cyclical actions have been recently debated in the area of motor control. We addressed questions concerning how components of variance within a redundant system (multi-digit pressing and prehension) change with increase in force rate in these two kinds of tasks. In experiment 1, during cyclical force production we found that the component of variance that affects task performance increased with force rate within a cycle. However, it did not increase with an increase in the task frequency. We explain this discrepancy within an earlier model as pointing at an ability of the central nervous system to adjust the timing parameter to achieve the same level of variability across different frequencies. In experiment 2, we used a discrete pressing task and found that the component of variance that affects task performance increased with force derivative both within a task and across tasks with different characteristic times. Taken together, results from the first two experiments suggest that the central nervous system is able to adjust the timing parameter in cyclical tasks but this ability is impaired in discrete tasks. In experiment 3, we studied both cyclical and discrete production of tangential force on a mechanically fixed object. We found that the force variance was higher for discrete tasks when compared with cyclical tasks. The component of variance that affects task performance showed a correlation with force rate, and the regression coefficient of the correlation dropped with task frequency for both types of actions. We found that this drop was faster for the cyclical actions. We found that these results were robust across two levels of an assumed control hierarchy of hand actions. In addition, we found that these results were true only for the task force but not the non-task (implicit) force. Overall, these results are consistent with the hypothesis on different control strategies for discrete and cyclical tasks.