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Testing hypotheses and the advancement of science: recent attempts to falsify the equilibrium point hypothesis

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Abstract

Criticisms of the equilibrium point (EP) hypothesis have recently appeared that are based on misunderstandings of some of its central notions. Starting from such interpretations of the hypothesis, incorrect predictions are made and tested. When the incorrect predictions prove false, the hypothesis is claimed to be falsified. In particular, the hypothesis has been rejected based on the wrong assumptions that it conflicts with empirically defined joint stiffness values or that it is incompatible with violations of equifinality under certain velocity-dependent perturbations. Typically, such attempts use notions describing the control of movements of artificial systems in place of physiologically relevant ones. While appreciating constructive criticisms of the EP hypothesis, we feel that incorrect interpretations have to be clarified by reiterating what the EP hypothesis does and does not predict. We conclude that the recent claims of falsifying the EP hypothesis and the calls for its replacement by EMG-force control hypothesis are unsubstantiated. The EP hypothesis goes far beyond the EMG-force control view. In particular, the former offers a resolution for the famous posture-movement paradox while the latter fails to resolve it.

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References

  • Asatryan DG, Feldman AG (1965) Functional tuning of the nervous system with control of movements or maintenance of a steady posture: I. Mechanographic analysis of the work of the joint on execution of a postural tasks. Biophysics 10:925–935

    Google Scholar 

  • Balasubramaniam R, Feldman AG (2004) Guiding movements without redundancy problems. In: Kelso S, Jirsa V (eds) Coordination dynamics: issues and trends. Springer, Berlin Heidelberg New York, p 155–176

  • Bellman R (1960) Introduction to matrix analysis. McGraw-Hill, New York

  • Bernstein NA (1935) The problem of interrelation between coordination and localization. Arch Biol Sci 38:1–35 (in Russian)

    Google Scholar 

  • Bhushan N, Shadmehr R (1999) Computational nature of human adaptive control during learning of reaching movements in force fields. Biol Cybern 81:39–60

    Article  CAS  PubMed  Google Scholar 

  • Bizzi E, Accornero N, Chapple W, Hogan N (1982) Arm trajectory formation in monkeys. Exp Brain Res 46:139–143

    Article  CAS  PubMed  Google Scholar 

  • Bizzi E, Hogan N, Mussa-Ivaldi FA, Giszter S (1992) Does the nervous system use equilibrium-point control to guide single and multiple joint movements? Behav Brain Sci 15:603–613

    Google Scholar 

  • Cannon SC, Zahalak GI (1982) The mechanical behavior of active human skeletal muscle in small oscillations. J Biomech 15:111–121

    Article  CAS  PubMed  Google Scholar 

  • Dizio P, Lackner JR (1995) Motor adaptation to Coriolis force perturbations of reaching movements: endpoint but not trajectory adaptation transfers to the nonexposed arm. J Neurophysiol 74:1787–1792

    CAS  PubMed  Google Scholar 

  • Feldman AG (1966) Functional tuning of the nervous system with control of movement or maintenance of a steady posture. II. Controllable parameters of the muscle. Biophysics 11:565–578

    Google Scholar 

  • Feldman AG (1979) Central and reflex mechanisms of motor control. Nauka, Moscow (in Russian)

  • Feldman AG (1986) Once more on the equilibrium-point hypothesis (λ model) for motor control. J Motor Behav 18:17–54

    CAS  Google Scholar 

  • Feldman AG (1993) The coactivation command for antagonist muscles involving Ib interneurons in mammalian motor control systems: an electrophysiologically testable model. Neurosci Lett 155:167–70

    Article  CAS  PubMed  Google Scholar 

  • Feldman AG, Latash ML (1982) Interaction of afferent and efferent signals underlying joint position sense: empirical and theoretical approaches. J Motor Behav 14:174–193

    CAS  Google Scholar 

  • Feldman AG, Levin MF (1995) The origin and use of positional frames of reference in motor control. Behav Brain Sci 18:723–806

    Google Scholar 

  • Feldman AG, Orlovsky GN (1972) The influence of different descending systems on the tonic stretch reflex in the cat. Exp Neurol 37:481–494

    Article  CAS  PubMed  Google Scholar 

  • Feldman AG, Adamovitch SV, Ostry DJ, Flanagan JR (1990) The origin of electromyograms—explanations based on the equilibrium point hypothesis. In: Winters JM, Woo SL-Y (eds) Multiple muscle systems. Biomechanics and movement organization. Springer, Berlin Heidelberg New York, pp 195–213

  • Feldman AG, Ostry DJ, Levin MF, Gribble PL, Mitnitski AB (1998) Recent tests of the equilibrium-point hypothesis (λ model). Motor Control 2:189–205

    CAS  PubMed  Google Scholar 

  • Ferris T (1977) The whole shebang. A state-of-the-universe(s) report. Simon & Schuster, New York, p 13)

  • Flanagan JR, Ostry DJ, Feldman AG (1993) Control of trajectory modifications in target-directed reaching. J Motor Behav 25:140–52

    Google Scholar 

  • Forget R, Lamarre Y (1987) Rapid elbow flexion in the absence of proprioceptive and cutaneous feedback. Hum Neurobiol 6:27–37

    CAS  PubMed  Google Scholar 

  • Franklin DW, Milner TE (2003) Adaptive control of stiffness to stabilize hand position with large loads. Exp Brain Res 152:211–220

    Article  PubMed  Google Scholar 

  • Gielen CCAM, van Bolhuis B (1995) Reciprocal and coactivation commands are not sufficient to describe muscle activation patterns. Behav Brain Sci 18:754–755

    Google Scholar 

  • Glansdorf P, Prigogine I (1971) Thermodynamic theory of structures, stability and fluctuations. Wiley, New York

  • Gomi H, Kawato M (1996) Equilibrium-point hypothesis examined by measured arm stiffness during multijoint movement. Science 272:117–120

    CAS  PubMed  Google Scholar 

  • Gottlieb GL (1996) On the voluntary movement of compliant inertial-viscoelastic loads by parcellated control mechanisms. J Neurophysiol 76:3207–3229

    CAS  PubMed  Google Scholar 

  • Gribble PL, Ostry DJ (1999) Compensation for interaction torques during single- and multijoint limb movement. J Neurophysiol 82:2310–2326

    CAS  PubMed  Google Scholar 

  • Gribble PL, Ostry DJ (2000) Compensation for loads during arm movements using equilibrium-point control. Exp Brain Res 135:474–482

    Article  CAS  PubMed  Google Scholar 

  • Gribble PL, Ostry DJ, Sanguineti V, Laboissiere R (1998) Are complex control signals required for human arm movements? J Neurophysiol 79:1409–1424

    CAS  PubMed  Google Scholar 

  • Gunther M, Ruder H (2003) Synthesis of two-dimensional human walking: a test of the lambda-model. Biol Cybern 89:89–106

    Article  PubMed  Google Scholar 

  • Hill AV (1938) The heat of shortening and the dynamic constants of muscle. P Roy Soc Lond B Bio 126:136–195

    Google Scholar 

  • Hinder MR, Milner TE (2003) The case for an internal dynamics model versus equilibrium point control in human movement. J Physiol 549:953–963

    Article  CAS  PubMed  Google Scholar 

  • Hollerbach JM (1982) Computers, brain, and the control of movements. Trends Neurosci 5:189–192

    Article  Google Scholar 

  • Jaric S, Milanovic S, Blezic S, Latash ML (1999) Changes in movement kinematics during single-joint movements against expectedly and unexpectedly changed inertial loads. Hum Movement Sci 18:49–66

    Article  Google Scholar 

  • Jobin A, Levin MF (2000) Regulation of stretch reflex threshold in elbow flexors in children with cerebral palsy: a new measure of spasticity. Dev Med Child Neurol 42:531–540

    Article  CAS  PubMed  Google Scholar 

  • Lackner JR, DiZio P (1994) Rapid adaptation to Coriolis force perturbations of arm trajectory. J Neurophysiol 72:1–15

    PubMed  Google Scholar 

  • Latash ML (1993) Control of human movement. Human Kinetics, Urbana, IL

  • Latash ML (1994) Control of fast elbow movement: a study of electromyographic patterns during movements against unexpectedly decreased inertial load. Exp Brain Res 98:145–152

    Article  CAS  PubMed  Google Scholar 

  • Latash ML, Gottlieb GL (1991) Reconstruction of elbow joint compliant characteristics during fast and slow voluntary movements. Neuroscience 43:697–712

    Article  CAS  PubMed  Google Scholar 

  • Latash ML, Zatsiorsky VM (1993) Joint stiffness: myth or reality? Hum Movement Sci 12:653–692

    Article  Google Scholar 

  • Lestienne FG, Thullier F, Archambault P, Levin MF, Feldman AG (2000) Multi-muscle control of head movements in monkeys: the referent configuration hypothesis. Neurosci Lett 283:65–68

    Article  CAS  PubMed  Google Scholar 

  • Levin MF, Dimov M (1997) Spatial zones for muscle coactivation and the control of postural stability. Brain Res 757:43-59

    Article  CAS  PubMed  Google Scholar 

  • Levin MF, Selles RW, Verheul MH, Meijer OG (2000) Deficits in the coordination of agonist and antagonist muscles in stroke patients: implications for normal motor control. Brain Res 853:352–369

    Article  CAS  PubMed  Google Scholar 

  • Merton PA (1953) Speculations on the servo-control of movements. In: Malcolm JL, Gray JAB, Wolstenholm GEW (eds) The spinal cord. Little Brown, Boston, MA, pp 183–198

  • Micheau P, Kron A, Bourassa P (2003) Evaluation of the lambda model for human postural control during ankle strategy. Biol Cyber 89:227–236

    Article  Google Scholar 

  • Ostry DJ, Feldman AG (2003) A critical evaluation of the force control hypothesis in motor control. Exp Brain Res 153:275–288

    Article  PubMed  Google Scholar 

  • Popescu FC, Rymer WZ (2000) End points of planar reaching movements are disrupted by small force pulses: an evaluation of the hypothesis of equifinality. J Neurophysiol 84:2670–2679

    CAS  PubMed  Google Scholar 

  • Popescu FC, Rymer WZ (2003) Implications of low mechanical impedance in upper limb reaching movements. Motor Control 7:323–327

    PubMed  Google Scholar 

  • Popescu FC, Hidler JM, Rymer WZ (2003) Elbow impedance during goal-directed movements. Exp Brain Res 152:17–28

    Article  PubMed  Google Scholar 

  • Rothwell JC, Traub MM, Marsden CD (1982) Automatic and “voluntary” responses compensating for disturbances of human thumb movements. Brain Res 248:33–41

    Article  CAS  PubMed  Google Scholar 

  • Shadmehr R, Mussa-Ivaldi FA (1994) Adaptive representation of dynamics during learning of a motor task. J Neurosci 14:3208–3224

    CAS  PubMed  Google Scholar 

  • Schmidt RA, McGown C (1980) Terminal accuracy of unexpected loaded rapid movements: evidence for a mass-spring mechanism in programming. J Motor Behav 12:149–161

    CAS  Google Scholar 

  • Schweighofer N, Arbib MA, Kawato M (1998) Role of the cerebellum in reaching movements in humans. I. Distributed inverse dynamics control. Eur J Neurosci 10:86–94

    Article  CAS  PubMed  Google Scholar 

  • Sherrington CS (1910) Flexion reflex of the limb, crossed extension reflex, and reflex stepping and standing. J Physiol 40:28–121

    Google Scholar 

  • St-Onge N, Feldman AG (2004) Referent configuration of the body: a global factor in the control of multiple skeletal muscles. Exp Brain Res 155:291–300

    Article  PubMed  Google Scholar 

  • St-Onge N, Adamovich SV, Feldman AG (1997) Control processes underlying elbow flexion movements may be independent of kinematic and electromyographic patterns: experimental study and modelling. Neuroscience 79:295–316

    Article  CAS  PubMed  Google Scholar 

  • Sternad D, Turvey MT (1995) Control parameters, equilibria, and coordination dynamics. Behav Brain Sci 18:780

    Google Scholar 

  • Stokes IA, Gardner-Morse MG (2000) Strategies used to stabilize the elbow joint challenged by inverted pendulum loading. J Biomech 33:737–743

    Article  CAS  PubMed  Google Scholar 

  • Toffin D, McIntire J, Droulez J, Kemeny A, Berthoz A (2003) Perception and reproduction of force direction in the horizontal plane. J Neurophysiol 90:3040–3053

    CAS  PubMed  Google Scholar 

  • Vallbo DB (1974) Human muscle spindle discharge during isometric voluntary contractions. Amplitude relations between spindle frequency and torque. Acta Physiol Scand 90:310–36

    Google Scholar 

  • Von Holst E, Mittelstaedt H (1950) Daz reafferezprincip. Wechselwirkungen zwischen Zentralnerven-system und Peripherie. Naturwiss 37:467–476 (The reafference principle. In: Martin R (translator)(1973) The behavioral physiology of animals and man. The collected papers of Erich von Holst. University of Miami Press, Coral Gables, Florida, 1, pp 139–173)

  • Wachholder K, Altenburger H (1927) Do our limbs have only one rest length? Simultaneously a contribution to the measurement of elastic forces in active and passive movements. Pflüg Arch 215:627–640 (Cited after: Sternad D (2002) Foundational experiments for current hypotheses on equilibrium point control in voluntary movements. Motor Control 6:299–318)

    Google Scholar 

  • Weber E (1846) Muskelbewegung. In: Wagner R (ed) Wagner’s Handwirterbuch der Physiologie, Friedrich Vieweg, Braunschweig, 3:1–122

  • Wolpert DM, Miall RC, Kawato M (1998) Internal models in the cerebellum. Trends Cogn Sci 2:338–347

    Article  Google Scholar 

  • Won J, Hogan N (1995) Stability properties of human reaching movements. Exp Brain Res 107:125–136

    Article  CAS  PubMed  Google Scholar 

  • Zatsiorsky VM, Duarte M (1999) Instant equilibrium point and its migration in standing tasks: rambling and trembling components of the stabilogram. Motor Control 3:28–38

    CAS  PubMed  Google Scholar 

  • Zatsiorsky VM, Duarte M (2000) Rambling and trembling in quiet standing. Motor Control 4:185–200

    CAS  PubMed  Google Scholar 

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Acknowledgements

AGF was supported by CIHR (Canada), NSERC (Canada), NOTEQ (Quebec), and MLL benefited from NIH grants AG-018751 and NS-35032.

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Correspondence to Anatol G. Feldman.

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Feldman, A.G., Latash, M.L. Testing hypotheses and the advancement of science: recent attempts to falsify the equilibrium point hypothesis. Exp Brain Res 161, 91–103 (2005). https://doi.org/10.1007/s00221-004-2049-0

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