Version 1
: Received: 10 February 2022 / Approved: 11 February 2022 / Online: 11 February 2022 (12:16:39 CET)
Version 2
: Received: 5 June 2022 / Approved: 6 June 2022 / Online: 6 June 2022 (09:17:09 CEST)
Dimitriou, M. Human Muscle Spindles Are Wired to Function as Controllable Signal-Processing Devices. eLife 2022, 11, doi:10.7554/elife.78091.
Dimitriou, M. Human Muscle Spindles Are Wired to Function as Controllable Signal-Processing Devices. eLife 2022, 11, doi:10.7554/elife.78091.
Dimitriou, M. Human Muscle Spindles Are Wired to Function as Controllable Signal-Processing Devices. eLife 2022, 11, doi:10.7554/elife.78091.
Dimitriou, M. Human Muscle Spindles Are Wired to Function as Controllable Signal-Processing Devices. eLife 2022, 11, doi:10.7554/elife.78091.
Abstract
Muscle spindles are encapsulated sensory organs found in most of our muscles. Prevalent models of human sensorimotor control assume the role of spindles is to reliably encode the mechanical state of muscle i.e., muscle stretch. Here, I argue that the traditional view of the spindle as a basic mechanoreceptor is outdated. Spindle organs can be independently tuned by spinal γ motor neurons that receive top-down and peripheral input, including from cutaneous afferents. I propose that spindles under efferent control play a flexible and higher-level role, providing a unique service to the nervous system: that of a peripheral signal-processing device that helps augment and expedite sensorimotor performance. Recent studies with naturalistically active humans support such a role, showing that spindle tuning enables the independent preparatory control of muscle compliance, the selective extraction of information during implicit motor adaptation, and for segmental stretch reflexes to operate in joint space. A new model of human sensorimotor control is presented, viewing γ motor activity as an intermediate coordinate transformation that allows different descending and peripheral information to project onto a common spindle-based coordinate frame. Incorporation of advanced signal-processing at the periphery may well prove a critical step in the evolution of sensorimotor control theories.
Keywords
muscle spindle; proprioception; sensorimotor; fusimotor; signal processing; human
Subject
Biology and Life Sciences, Anatomy and Physiology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
