To understand how olfactory information controls certain behaviors, it is necessary identify neural elements in the central nervous system that process and relay olfactory information and to determine the mechanisms by which such elements exert their influence over particular motor acts. In favorable invertebrate preparations, the sensory afferent pathways and the neural elements that govern stereotyped behaviors are accessible to cellular study. These systems therefore serve as useful models for studies of neural mechanisms leading from sensory inputs to motor outputs. As has been demonstrated in numerous important cases, insights gained from such model systems can provide a basis for, and guide research on, less accessible vertebrate systems. One such useful model is the moth Manduca sexta, in which detection of certain chemical cues by antennal olfactory receptors stimulates stereotyped behaviors. For example, the sex pheromones released by a receptive female trigger a characteristic flight response in a male, by which he orients and moves toward, and eventually finds the signalling female for mating. Olfactory information about sex pheromones is processed in a specialized part of the brain that is found only in the antennal lobes of normal males and gynandromorphic females (with antennal lobes innervated by sensory axons from male antennae). Olfactory information integrated in these and other, """"""""higher"""""""" brain centers ultimately descends to thoracic motor centers and to control flight. By means of intracellular recording and staining, this research will explore the physiology and structure of nerve cells in the pathway from olfactory centers in the brain to the flight-motor outputs in the thorax. The proposed studies will focus on: (1) the control of flight motor activity by odors (particularly sex pheromones) delivered to the antennae; (2) descending projection neurons that carry the integrated olfactory information from the brain to motor centers in the thoracic ganglia of males and gynandromorphic females; and (3) the roles of identifiable neurons in the thoracic ganglia as targets of the descending projection neurons and as possible modulators of flight motor activity. This research promises to expand our understanding of neural mechanisms of olfaction as well as of motor control. Learning about the mechanisms by which olfactory information exerts control over important behaviors in such a model system will help to fill a major gap in our understanding of the chemical senses and their roles in normal and abnormal neural and behavioral functions.
