-016-4757-7 Ambike , S. , Zhou , T. , Zatsiorsky , V.M. , & Latash , M.L. ( 2015 ). Moving a hand-held object: Reconstruction of referent coordinate and apparent stiffness trajectories . Neuroscience, 298, 336 – 356 . PubMed ID: 25896800 doi:10.1016/j.neuroscience.2015.04.023 10.1016/j
Search Results
On Primitives in Motor Control
Mark L. Latash
Abundant Degrees of Freedom Are Not a Problem
Mark L. Latash
of the muscle leads to shifts of ? with no major change in the shape of the F(L) dependence. The magnitude of λ may be viewed as a referent length (referent coordinate [RC]) for the muscle, which it would reach in the absence of external resistance. The idea of control with RCs has been generalized
Optimality, Stability, and Agility of Human Movement: New Optimality Criterion and Trade-Offs
Mark L. Latash
force of the agonist and antagonist muscles along X is zero (open circle, RC for the effector). The C -command defines a spatial range where both agonist and antagonist muscles show nonzero activation. RC = referent coordinate; MU = motor units. Recently, the idea of control with RC has been
Motor Control: Creating a Natural Science of Biological Movement
Mark L. Latash
. Then, the idea of parametric control was expanded to movements of arbitrary multimuscle systems up to the whole body ( Feldman, 2015 ; Latash, 2019 ). This step required the introduction of the concept of a spatial referent coordinate (RC) as a multidimensional parameter that links the force vector
Intramuscle Synergies: Their Place in the Neural Control Hierarchy
Mark L. Latash, Shirin Madarshahian, and Joseph M. Ricotta
the central nervous system and from peripheral sensory endings. RC = referent coordinate; MU = motor unit. Numerous experimental studies, starting from the classical experiment by Bernstein ( 1930 ) of professional blacksmiths have demonstrated that natural movements, including highly skilled ones
The Nature of Finger Enslaving: New Results and Their Implications
Valters Abolins and Mark L. Latash
We present a review on the phenomenon of unintentional finger action seen when other fingers of the hand act intentionally. This phenomenon (enslaving) has been viewed as a consequence of both peripheral (e.g., connective tissue links and multifinger muscles) and neural (e.g., projections of corticospinal pathways) factors. Recent studies have shown relatively large and fast drifts in enslaving toward higher magnitudes, which are not perceived by subjects. These and other results emphasize the defining role of neural factors in enslaving. We analyze enslaving within the framework of the theory of motor control with spatial referent coordinates. This analysis suggests that unintentional finger force changes result from drifts of referent coordinates, possibly reflecting the spread of cortical excitation.
Biological Movement and Laws of Physics
Mark L. Latash
Living systems may be defined as systems able to organize new, biology-specific, laws of physics and modify their parameters for specific tasks. Examples include the force-length muscle dependence mediated by the stretch reflex, and the control of movements with modification of the spatial referent coordinates for salient performance variables. Low-dimensional sets of referent coordinates at a task level are transformed to higher-dimensional sets at lower hierarchical levels in a way that ensures stability of performance. Stability of actions can be controlled independently of the actions (e.g., anticipatory synergy adjustments). Unintentional actions reflect relaxation processes leading to drifts of corresponding referent coordinates in the absence of changes in external load. Implications of this general framework for movement disorders, motor development, motor skill acquisition, and even philosophy are discussed.
Systematic, Unintended Drifts in the Cyclic Force Produced with the Fingertips
Satyajit Ambike, Daniela Mattos, Vladimir Zatsiorsky, and Mark Latash
human motor actions (reviewed in Latash, 2016 ). According to this approach, force production in isometric conditions is associated with setting a referent coordinate (RC) for the effector and a magnitude of apparent stiffness ( k , which is a reflection of shifts in spatial RCs for the participating
Improved Learning a Coincident Timing Task With a Predictable Resisting Force
Arturo Forner-Cordero, Virgínia H. Quadrado, Sitsofe A. Tsagbey, and Bouwien C.M. Smits-Engelsman
predictability of the forces. Nevertheless, there could be alternative interpretations such as learning a desired timing for the trajectory of the referent coordinate for the hand. It is possible to see learning in the movement as the change of equilibrium positions of agonist antagonist groups of muscles. This
Human Movement: In Search of Borderlands Between Philosophy and Physics
Scott Kretchmar and Mark L. Latash
generalized for movements of any effectors, up to the whole body, using the concept of spatial referent coordinate (RC) for any effector as the parameter in respective laws of nature ( Latash, 2010 , 2017 ). To produce an action, time changes in the relatively low-dimensional RC at the task level are
