T. Jellema et Wj. Heitler, Central and peripheral control of the trigger mechanism for kicking and jumping in the locust, J COMP NEUR, 404(2), 1999, pp. 212-220
A crucial stage of the locust kick motor program is the trigger activity th
at inhibits the flexor motorneurons at the end of flexor-extensor coactivat
ion and releases the tibia. One source of this inhibition is the M interneu
ron, which produces a spike burst at the time of the trigger activity. Prev
ious work has suggested that sensory input resulting from extensor muscle t
ension may contribute to the M spike burst. We find that extensor muscle te
nsion produced during thrusting behavior or by direct electrical stimulatio
n with the tibia held fixed results in the depolarization of M, but this is
not of sufficient amplitude to account for the M spike burst during the tr
igger activity. Furthermore, M still produces a spike burst after ablating
the sensory systems that produce the response to the muscle stimulation. It
is concluded that the major component of the M trigger activity is central
in origin, although sensory feedback from extensor muscle tension makes so
me contribution. The combination of both central and peripheral paths for M
activation may enhance the robustness of the behavior. (C) 1999 Wiley-Liss
, Inc.