Neural control of leg movements in a metamorphic insect: sensory and motor elements of the larval thoracic legs in XXXX .

@entity4079 @entity2343 @entity21 @entity1953 @entity528
During the metamorphosis of the hawkmoth @entity4079 the larval thoracic legs degenerate to be replaced in the adult by legs of very different form and function. This change must be accompanied by a reorganization of the neural circuits controlling leg movements. As an initial step in the study of this reorganization we describe here the sensory and motor elements of this circuitry in the larval stage of life. Sensory neurons innervating mechanoreceptive hairs on the thoracic surface were stained individually with @entity1953 . Those innervating hairs on the general thoracic surface project topographically into two ventral regions of the segmental @entity21 . @entity528 also map topographically to the more ventral of these regions but in addition have arborizations in a midlateral region. The density of branching within this lateral "leg neuropil" is greatest for sensory neurons form sensilla on the more distal leg segments. Leg motor neurons were identified with intracellular recording and @entity1953 injection techniques. Those innervating muscles controlling distal leg segments have dense @entity2343 in the lateral "leg neuropil," while motor neurons controlling more proximal segments and muscles of the ventral body wall have extensive arborizations in a dorsomedial region of the ganglion. In general, flexor motor neurons are excited by medial and inhibited by lateral leg sensilla, while the opposite is true of extensors. @entity528 respond most strongly to sensory neurons from distal segments, thus suggesting some interaction within the lateral "leg neuropil." Thus, in the larval nervous system a highly ordered array of of sensory and motor elements underlies the specific behavioral responses of the legs to tactile stimulation.
