Multifinger manipulation requires interactions among numerous muscles to produce the necessary fingertip motions and forces. The muscles of the fingers (including the thumb) are considered redundant. Redundancy, which has long been called the central problem of motor control, also suggests robustness to loss of some muscles. Our work to date compels and enables us to systematically establish how the interactions among muscles within a finger, and the fingers within a grasp, fail to be robust to muscle dysfunction. Each Hypothesis and Aim addresses the production of a fundamental, yet currently not understood, component of multifinger grasp: slow finger motions and grasp equilibrium. To test each Hypothesis we will apply and extend our integrative approach combining behavioral studies, cadaveric experiments, mathematical analysis, and biomechanical modeling in two complementary Aims.
Aim 1 : Characterize the necessary mechanical interactions among finger muscles for motion;and quantify their robustness to loss of specific muscles. We will focus on how tendon tensions affect the feasibility of slow motions of the thumb, index and middle fingers for grasp acquisition. Hypothesis I: Lack of redundancy for grasp acquisition and release: Slow finger motions are not robust to loss of some muscles.
Aim 2 : Characterize the necessary interactions among tendon tensions for multifinger grasp equilibrium;and quantify their robustness to loss of specific muscles. We will focus on how tensions from individual muscles affect the equilibrium of two- and three-finger precision grasps (using the tips of thumb:index;and thumb:index:middle). We will also explore how simulated signal-dependent noise affects grasp equilibrium. Primary Hypothesis IIa: Lack of redundancy for static grasp forces: Grasp equilibrium is not robust to loss of some muscles. Secondary Hypothesis Hypothesis IIb: Lack of redundancy for static grasp forces: Muscle Signal- Dependent Noise further compromises grasp equilibrium. The understanding gained about multifinger grasp in this project will provide the much-needed neuro- mechanical foundation to understand the vulnerability (and rehabilitation) of dexterous manipulation in specific orthopedic/neurologic diseases, development and aging.

Public Health Relevance

Using our fingers to grasp and hold objects is necessary for us to perform most of our activities of daily living. However, because the anatomy of the hand is so complex, there is little known about how each muscle of the fingers contributes to grasping function. Our proposed project will combine anatomical studies, engineering science and clinical know-how to establish which muscles are most important, and therefore should be most protected, to improve the hand function of people suffering from the many disabilities of the hand.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Motor Function, Speech and Rehabilitation Study Section (MFSR)
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Boyce, Amanda T
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University of Southern California
Biomedical Engineering
Schools of Engineering
Los Angeles
United States
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Dayanidhi, Sudarshan; Valero-Cuevas, Francisco J (2014) Dexterous manipulation is poorer at older ages and is dissociated from decline of hand strength. J Gerontol A Biol Sci Med Sci 69:1139-45
Lyle, Mark A; Valero-Cuevas, Francisco J; Gregor, Robert J et al. (2014) Control of dynamic foot-ground interactions in male and female soccer athletes: females exhibit reduced dexterity and higher limb stiffness during landing. J Biomech 47:512-7
Dayanidhi, Sudarshan; Kutch, Jason J; Valero-Cuevas, Francisco J (2013) Decrease in muscle contraction time complements neural maturation in the development of dynamic manipulation. J Neurosci 33:15050-5
Dayanidhi, Sudarshan; Hedberg, Asa; Valero-Cuevas, Francisco J et al. (2013) Developmental improvements in dynamic control of fingertip forces last throughout childhood and into adolescence. J Neurophysiol 110:1583-92
Kurse, Manish U; Lipson, Hod; Valero-Cuevas, Francisco J (2012) Extrapolatable analytical functions for tendon excursions and moment arms from sparse datasets. IEEE Trans Biomed Eng 59:1572-82
Kutch, Jason J; Valero-Cuevas, Francisco J (2011) Muscle redundancy does not imply robustness to muscle dysfunction. J Biomech 44:1264-70
Mosier, Kristine; Lau, Chad; Wang, Yang et al. (2011) Controlling instabilities in manipulation requires specific cortical-striatal-cerebellar networks. J Neurophysiol 105:1295-305
Holmstrom, Linda; de Manzano, Orjan; Vollmer, Brigitte et al. (2011) Dissociation of brain areas associated with force production and stabilization during manipulation of unstable objects. Exp Brain Res 215:359-67
Cianchetti, Flor A; Valero-Cuevas, Francisco J (2010) Anticipatory control of motion-to-force transitions with the fingertips adapts optimally to task difficulty. J Neurophysiol 103:108-16
Sherback, Michael; Valero-Cuevas, Francisco J; D'Andrea, Raffaello (2010) Slower visuomotor corrections with unchanged latency are consistent with optimal adaptation to increased endogenous noise in the elderly. PLoS Comput Biol 6:e1000708

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