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J Neurophysiol. 2014 Sep 15;112(6):1376-91. doi: 10.1152/jn.00663.2013. Epub 2014 Jun 3.

Stabilization of cat paw trajectory during locomotion.

Author information

1
School of Applied Physiology, Center for Human Movement Studies, Georgia Institute of Technology, Atlanta, Georgia;
2
Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and.
3
Department of Kinesiology, Penn State University, University Park, Pennsylvania.
4
School of Applied Physiology, Center for Human Movement Studies, Georgia Institute of Technology, Atlanta, Georgia; boris.prilutsky@ap.gatech.edu.

Abstract

We investigated which of cat limb kinematic variables during swing of regular walking and accurate stepping along a horizontal ladder are stabilized by coordinated changes of limb segment angles. Three hypotheses were tested: 1) animals stabilize the entire swing trajectory of specific kinematic variables (performance variables); and 2) the level of trajectory stabilization is similar between regular and ladder walking and 3) is higher for forelimbs compared with hindlimbs. We used the framework of the uncontrolled manifold (UCM) hypothesis to quantify the structure of variance of limb kinematics in the limb segment orientation space across steps. Two components of variance were quantified for each potential performance variable, one of which affected it ("bad variance," variance orthogonal to the UCM, VORT) while the other one did not ("good variance," variance within the UCM, VUCM). The analysis of five candidate performance variables revealed that cats during both locomotor behaviors stabilize 1) paw vertical position during the entire swing (VUCM > VORT, except in mid-hindpaw swing of ladder walking) and 2) horizontal paw position in initial and terminal swing (except for the entire forepaw swing of regular walking). We also found that the limb length was typically stabilized in midswing, whereas limb orientation was not (VUCM ≤ VORT) for both limbs and behaviors during entire swing. We conclude that stabilization of paw position in early and terminal swing enables accurate and stable locomotion, while stabilization of vertical paw position in midswing helps paw clearance. This study is the first to demonstrate the applicability of the UCM-based analysis to nonhuman movement.

KEYWORDS:

accurate stepping; cat; principle of abundance; uncontrolled manifold analysis; walking

PMID:
24899676
PMCID:
PMC4137248
DOI:
10.1152/jn.00663.2013
[Indexed for MEDLINE]
Free PMC Article

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