Journal of Neurophysiology, Vol 57, Issue 2 343-356, Copyright © 1987 by APS
Correlation analysis of muscle receptor discharge during active contractions of the cat medial gastrocnemius muscle
C. E. Osborn and M. D. Binder
The spike trains of afferent fibers innervating muscle spindles and Golgi
tendon organs in the medial gastrocnemius muscle were recorded during
spontaneous contractions in either decerebrate cats or decapitate cats
treated with L-dopa. For each afferent fiber, the approximate location of
its receptor within the muscle was determined. Cross-correlation histograms
were compiled from the simultaneously recorded spike trains of pairs of
afferent fibers (Ia, Ib, spindle II) to determine if the degree of temporal
correlation in their discharge was related to the mutual proximity of the
receptors they innervated within the muscle. The frequency of occurrence
and degree of correlated activity between pairs of muscle afferents,
regardless of receptor type, was much greater in the decerebrate
preparations than in the decapitate-L-dopa preparations. However, in all
cases, the extent of correlated activity appeared to be unrelated to the
relative locations of the receptors. The results suggest that the degree to
which the discharge patterns of muscle receptors display temporal
correlations and thereby potentially reinforce the "sensory partitioning"
(5) of their parent muscle is strongly dependent on the type of preparation
used, and thus by inference, dependent on the central state of the animal.
