PHEROMONE-TRIGGERED FLIPFLOPPING NEURAL SIGNALS CORRELATE WITH ACTIVITIES OF NECK MOTOR-NEURONS OF A MALE MOTH, BOMBYX-MORI

Male silkworm moths, Bombyx mori, exhibited sidewise movements of the head when they showed zigzagging walking in response to pheromonal sti mulation. When the moth changed the direction of walking, the head ang les also changed to those associated with the walking direction. The s idewise movements of the head were thought to be regulated by neck mot or neurons which innervated the first cervical ventral muscles and the ventral muscles through a second cervical nerve. It has been reported that the state transition, resembling the 'flipflop' operation of an electrical circuit, in the spike activity of descending interneurons r unning in the ventral nerve cord to a thoracic motor system appears to be important in the pheromone-modulated turning of male B. mori. We r ecorded the activity of neck motor neurons in the second cervical nerv e and the flipflopping activity in the ventral nerve cord simultaneous ly with multiple suction electrodes, in order to clarify the physiolog ical functions of such flipflopping signals involved in the behavior. We demonstrated that the activity pattern of some neck motor neurons w as correlated with the state transition of a flipflopping activity pat tern triggered by the pheromones. The result suggests that the flipflo pping activity pattern is correlated with the instruction of the zigza g turning during the pheromone-mediated walking of B. mori males.