Blockade of neurotransmission in Drosophila mushroom bodies impairs odor attraction, but not repulsion.

Olfaction can elicit a rich perceptual experience. It is not known, however, whether olfactory information is decomposed into various components and processed in distinct perceptual centers as in other sensory systems, such as vision, where neural representations of different visual sensations are segregated in different cortical regions, despite the fact that multiple structures of the primary olfactory cortex receive projections from the olfactory bulb. Here, we use Drosophila as a model to investigate whether different olfactory information may be processed in separate brain structures. Organizations of the peripheral olfactory system are remarkably similar from mammals to insects. As in vertebrates, the olfactory pathway in Drosophila follows similar convergence and divergence, and multiple high-order structures in the Drosophila brain, including the mushroom body (MB) and lateral horn (LH) of the protocerebrum, receive olfactory input. We specifically blocked neurotransmission in the MB while leaving the LH unaffected and examined its effect on olfactory avoidance and attraction behaviors. We show that blocking MB activity disrupted responses to attractive, but not repulsive, odors, and this finding suggests that attractive and repulsive olfactory information may be separately processed in higher olfactory centers of the Drosophila brain.