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Intermittency between grip force and load force

Grover, Francis M
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522334274008361

Abstract Details

2018, MA, University of Cincinnati, Arts and Sciences: Psychology.
Tightly coordinated grip force adaptations in response to changing load forces have been reported as continuous, stable, and proportional to the load force changes. Considering the existence of inherent sensorimotor feedback delays, current accounts of grip force-load force coupling invoke explicit predictive mechanisms in the form of internal models for feedforward control to account for anticipatory grip force modulations. However, recent findings show that grip force-load force coupling is less stable and regular than previously thought. When load force variations are more diminished, grip force is adjusted only intermittently and with less responsiveness, rather than adjusted continuously and proportionally. This has several implications for current accounts of grip force-load force coupling, and more broadly for accounts of anticipation in motor control. The objective of the current study was to quantify the time-varying characteristics of grip force in response to differentially changing load force, and to investigate how the intermittent responsiveness of grip force is tuned to changes in load force magnitude and predictability. A second aim of the study was to investigate grip force-load force coupling in a task where the participant’s focus was not directed toward explicitly controlling grip force; given that the ability to maintain grasp of hand-held objects persists in daily life without constant explicit control, it is noteworthy that no existing studies have examined GF-LF coupling in an implicit context. Twenty-three undergraduate students from the University of Cincinnati grasped a cylindrical object with their right thumb and forefinger and moved the object in order to track a moving target presented in virtual reality. In moving the object to track the target, participants produced changes in the load force exerted by the object on their grasp, for which their grip force had to be adjusted to prevent the object from slipping. The target moved in either a highly regular (sinusoidal), stochastic (fractional Brownian motion (fBm), i.e., random walk), or deterministic but chaotic fashion (i.e., the chaotic Lorenz system), which resulted in load force changes with varying degrees of predictability. Different amounts of mass (60 g and 120 g) were added to the object as a second manipulation to influence the magnitude of load force variation. The results confirmed the finding of Grover, Lamb, Bonnette, Silva, Lorenz, & Riley (submitted) that grip force-load force coupling was not continuous and stable over the course of a trial, and that the strength and stability of the coupling increased as load force changes became less predictable and their magnitudes became more enhanced. In addition, the intermittency observed in grip force-load force coupling was found to extend to the temporal relation between grip force to load force, which varied from anticipatory, to lagged, to complete coordination with load force, over the course of individual trials. These insights raise several important issues for the internal model account of grip force-load force coupling and suggest instead that a complex dynamical system approach, such as an anticipatory synchronization or delay differential equation model, may be necessary to further develop a comprehensive account of the anticipatory nature of grip force-load force coupling and other anticipatory phenomena in sensorimotor control.
Michael Riley, Ph.D. (Committee Chair)
Tamara| Lorenz, Ph.D. (Committee Member)
Paula Silva, Ph.D. (Committee Member)
47 p.
Behavioral Sciences
Motor control; Coordination; Grip force; Load force; Intermittency; Anticipation

Recommended Citations

Citations

  • Grover, F. M. (2018). Intermittency between grip force and load force [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522334274008361

    APA Style (7th edition)

  • Grover, Francis. Intermittency between grip force and load force. 2018. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522334274008361.

    MLA Style (8th edition)

  • Grover, Francis. "Intermittency between grip force and load force." Master's thesis, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522334274008361

    Chicago Manual of Style (17th edition)

ucin1522334274008361
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This open access ETD is published by University of Cincinnati and OhioLINK.