|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1994 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1993 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Male silkworm moth, Bombyx mori, display oriented upwind zigzagging walking accompanying wing vibration in response to the sex pheromones of receptive conspecific females. We suggested that the wing vibration as well as the walking toward the pheromone source are controlled by a self-generated zigzag turning program which is triggered by intermittent pheromonal stimulation applied to the antennae. In order to understand the behavioral and neural mechanisms of such an innate behavior, we have studied how information about the pheromones is processed in the olfactory neural system of the brain and how this information participates in generating and controlling the zigzagging behavior.
we found that olfactory neurons in the protocerebrum (PC) , the higher olfactory integrative centers, innervate a particular neuropil region, the lateral accessory lobe (LAL). Each LAL is also linked with each other through the commissure of LALs. The LALs may be interposed in the pathways of olfactory information flow, from the first-order olfactory center, the antennal lobe, through the lateral PC to the interneurons descending (DNs) to the thoracic motor center (TMC) via the ventral nerve cord (VNC).
Some LAL DNs showed state-dependent activities, like an electronic 'flip-flop', which have two distinct firing frequencies, high and low. Switching back and forth between the two states occurs upon sequential pheromonal stimulation previously characterized by Olberg (1983). Two clusters (group I,II) of DNs which have arborizations in the LAL were examined and two types of flip-flop activities, which have an antiphasic relationship, descending in each of the VNC to the TMC were found. These findings provide a substrate for understanding the olfactory neural system required to produce flip-flop activities, which may be an important signal to control zigzagging behavior.