Pheromone-modulated optomotor response in male gypsy moths, Lymantria dispar L.: Directionally selective visual interneurons in the ventral nerve cord

Summary

In response female pheromone the male gypsy moth flies a zigzagging path upwind to locate the source of odor. He determines wind direction visually. To learn more about the mechanism underlying this behavior, we studied descending interneurons with dye-filled micro-electrodes. We studied the interneuronal responses to combinations of pheromone and visual stimuli.

• 1. We recorded 5 neurons whose directionally selective visual responses to wide field pattern movement were amplified by pheromone (Figs. 2–6).

• 2. The activity of the above neurons was more closely correlated with the position of the moving pattern than with its velocity (Fig. 4).

• 3. One neuron showed no clearly directional visual response and no response to pheromone. Yet in the presence of pheromone it showed directionally selective visual responses (Fig. 6).

• 4. We recorded 4 neurons whose directionally selective visual responses were not modulated by pheromone (Fig. 7), ruling out the possibility that the effect of the pheromone was simply to raise the activity of all visual neurons.

• 5. Our results suggest that female pheromone amplifies some neural pathways mediating male optomotor responses, especially the directionally selective responses to the transverse movement of the image, both below and above the animal.