Diverse and complex muscle spindle afferent firing properties emerge from multiscale muscle mechanics

Kyle P. Blum, Kenneth S. Campbell, Brian C. Horslen, Paul Nardelli, Stephen N. Housley, Timothy C. Cope, Lena H. Ting

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Despite decades of research, we lack a mechanistic framework capable of predicting how movement-related signals are transformed into the diversity of muscle spindle afferent firing patterns observed experimentally, particularly in naturalistic behaviors. Here, a biophysical model demonstrates that well-known firing characteristics of mammalian muscle spindle la afferents-including movement history dependence, and nonlinear scaling with muscle stretch velocity-emerge from first principles of muscle contractile mechanics. Further, mechanical interactions of the muscle spindle with muscle-tendon dynamics reveal how motor commands to the muscle (alpha drive) versus muscle spindle (gamma drive) can cause highly variable and complex activity during active muscle contraction and muscle stretch that defy simple explanation. Depending on the neuromechanical conditions, the muscle spindle model output appears to ‘encode’ aspects of muscle force, yank, length, stiffness, velocity, and/or acceleration, providing an extendable, multiscale, biophysical framework for understanding and predicting proprioceptive sensory signals in health and disease.

Original languageEnglish
Article numbere55177
Pages (from-to)1-32
Number of pages32
StatePublished - Dec 2020

Bibliographical note

Funding Information:
This was supported by Eunice Kennedy Shriver Na-tional Institute of Child Health and Human DevelopmentR01 HD90642 Kenneth S Campbell Timothy C Cope Lena H Ting National Cancer InstituteR01 CA221363 Timothy C Cope National Institute of Neurolo-gical Disorders and StrokeF31 NS093855 Kyle P Blum Government of CanadaBPF-156622 Brian C Horslen

Publisher Copyright:
© Blum et al.

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology (all)
  • Immunology and Microbiology (all)
  • Neuroscience (all)


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