Neural mechanisms underlying behavior in the locust <i>Schistocerca gregaria</i> III. Topography of limb motorneurons in the metathoracic ganglion

Abstract

Abstract Somata of 26 of the motorneurons situated on the right side of the metathoracis ganglion of the locust S. gregaria were identified by correlating their electrical activity with extracellularly or intracellularly recorded muscle potentials evoked either reflexly or by direct elctrical stimulation of the somata through the recording microelectrode. The neurons identified included most of those innervating the major leg muscles. Each neuron occupies a relatively fixed site on the ventral surface of the ganglion. The identified neurons were filled with procion yellow, the ganglia fixed and photographed as whole mounts, and then serially sectioned to determine the three dimensional topography of the major dendrites and the pathway of the axons through the neuropil. The topographical features of individual motorneurons were sufficiently characteristic to permit identification, Nevertheless, it was not found possible to classify the neurons on the basis of branching pattern. There is no relation between location in the ganglion and the muscle innervated, but locomotor motorneurons are clustered togethers in anterior, ventral, and lateral pockets.