Discrimination of sex pheromone blends in the olfactory system of the moth

Intracellular analysis of olfactory neurons in the internal lobes of several speicies of months has revealed a psysiologisally divorse population of projection neurons connecting the pheromone-processing center (the male-specific macroglormerular complex) with several area of the protocerebrum. Some of these output elements carry information about only a single pheromone in the female's complex blend, which is consistent with the 'component hypothesis' of behavioral excitation. Other output neurons, which receive more complex synaptic input, can distinguish the complete blend from the individual pheromones, thereby lending support to the 'blend hypothesis' of behavioral excitation. The results suggest that even within the pheromone-processing subsysterm in male insects, which is largely distinct from the rest of the olfactory system, there exist different but parallel lines of pheromonal information coding that ultimately govern the steteotyped mate-seeking behaviors.