Journal of Neurophysiology, Vol 38, Issue 2 313-331, Copyright © 1975 by APS
Analysis of postural motoneuron activity in crayfish abdomen. I. Coordination by premotoneuron connections
P. G. Sokolove and W. G. Tatton
The activity of the crayfish abdominal postural motoneurons and their
associated neurons (the accessory neuron(s) and the MRO(1)) were examined
with the aid of techniques for the analysis of simultaneously recorded
spike trains. A means of reliably identifying the spikes of the individual
motoneurons based on their relative axon conduction velocities is
presented. The analyses show that: 1) the large, phasically active
synergist motoneurons innervating muscles producing the same movement show
a marked similarity in their average responses, which is independent of the
input source; 2) the small, tonically active and the middle-sized,
tonicphasic synergist motoneurons innervating the same muscle and similar
synergist motoneurons innervating antagonistic muscles are coordinated
entirely by premotoneuron connections; 3) the accessory neuron is
coordinated in its activity with the phasically active flexor excitor
motoneurons and the extensor inhibitor motoneuron and thereby functions as
a flexor synergist; and 4) the simultaneous presentation of
flexion-producing and extension-producing inputs to the postural system
results in a reciprocal oscillation in flexor-extensor motoneuron output.
The functional significance of these results with respect to the operation
of the postural system are discussed.
