Position sensitivity of feline paraspinal muscle spindles to vertebral movement in the lumbar spine

Muscle spindles contribute to sensorimotor control by supplying feedback regarding muscle length and consequently information about joint position. While substantial study has been devoted to determining the position sensitivity of spindles in limb muscles, there appears to be no data on their sensitivity in the low back. We determined the relationship between lumbar paraspinal muscle spindle discharge and paraspinal muscle lengthening estimated from controlled cranialward movement of the L(6) vertebra in anesthetized cats. Ramp (0.4 mm/s) and hold displacements (0.2, 0.4, 0.6, 0.8, and 1.2 mm for 2.5 s) were applied at the L(6) spinous process. Position sensitivity was defined as the slope of the relationship between the estimated increase in muscle length and mean instantaneous frequency at each length. To enable comparisons with appendicular muscle spindles where joint angle was measured, we also calculated sensitivity in terms of the L(6) and L(7) intervertebral flexion angle (IVA). This angle was estimated from measurements of facet joint capsule strain (FJC) based on a previously established relationship between IVA and FJC strain in the cat lumbar vertebral column during lumbar flexion. Single-unit recordings were obtained from 12 muscle spindle afferents. Longissimus and multifidus muscles contained the receptive field of 10 and 2 afferents, respectively. Mean position sensitivity was 16.3 imp.s(-1).mm(-1) [10.6-22.1, 95% confidence interval (CI), P < 0.001]. Mean angular sensitivity was 5.2 imp.s(-1). degrees (-1) (2.6-8.0, P < 0.003). These slope estimates were more than 3.5 times greater compared with appendicular muscle spindles, and their CIs did not contain previous slope estimates for the sensitivity of appendicular spindles from the literature. Potential reasons for and the significance of the apparently high position sensitivity in the lumbar spine are discussed.

Cao, Dong-Yuan
Pickar, Joel G.
Ge, Weiginq
Ianuzzi, Allyson
Khalsa, Partap S.
Item Type: 
Journal Article
Publication Title: 
Journal of Neurophysiology
Journal Abbreviation: 
J. Neurophysiol.
Publication Date: 
Apr 2009
Publication Year: 
Library Catalog: 
NCBI Published Medical (?)
PMID: 19164108 PMCID: PMC2695637

Turabian/Chicago Citation

Dong-Yuan Cao, Joel G. Pickar, Weiginq Ge, Allyson Ianuzzi and Partap S. Khalsa. Apr 2009. "Position sensitivity of feline paraspinal muscle spindles to vertebral movement in the lumbar spine." Journal of Neurophysiology 101: 4: 1722-1729. 10.1152/jn.90976.2008.

Wikipedia Citation

<ref> {{Cite journal | doi = 10.1152/jn.90976.2008 | issn = 0022-3077 | volume = 101 | pages = 1722-1729 | last = Cao | first = Dong-Yuan | coauthors = Pickar, Joel G., Ge, Weiginq, Ianuzzi, Allyson, Khalsa, Partap S. | title = Position sensitivity of feline paraspinal muscle spindles to vertebral movement in the lumbar spine | journal = Journal of Neurophysiology | date = Apr 2009 | pmid = | pmc = }} </ref>