Morphology of neurons in locust brain and suboesphageal ganglion involved in initiation and maintenance of walking

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Abstract
Electrical stimulation through a glass microelectrode positioned in the neck or circumesophageal (co.) connective can evoke walking in a tethered locust. Cobalt nitrate was injected through the stimulating electrode to stain the involved neurons extracellularly. The cobalt travelled from injections at stimulating positions in the co. connective to stain fibers in the brain and subesophageal ganglion (so.g.). Injections in the neck connectives stained fibers in the so.g. and prothoracic ganglion. In the brain, neurons stained from co. connective positions where walking forwards, walking backwards or turning had been evoked branched predominantly in the dorsal deutocerebrum. In stains where sideways walking was evoked there was more branching in the lateral protocerebrum than in the deutocerebrum. Primary sensory fibers, particulary those in the dorsal tegumentary nerve, were often stained. These also branch in the dorsal deutocerebrum before descending. The so.g. contributes its own plurisegmental fibers, which may be ascending or both. Many fibers branched bilaterally.