224 INTEGRATIVE BIOLOGY ARTICLES ARTICLES Integrating Behavior With Neurobiology: Odor-Mediated Moth Flight and Olfactory Discrimination by Glomerular Arrays NEIL J. VICKERS,* THOMAS A. CHRISTENSEN, AND JOHN G. HILDEBRAND Animals are equipped with a variety of sensory systems that allow them to extract information from the environ- ments they inhabit. The ability to detect the chemical environment is probably the most ancient sense. The sense of smell can provide important details about the habitat because chemical signals emitted by both beneficial and po- tentially harmful sources can be detected and appropriate behavior initiated without relying upon input from other sensory modalities. Even though olfactory communication can be slow compared to other sensory modalities such as vision and sound, it is sometimes very reliable and stable (e.g. trail or territory marking) and in other circumstances may be much more ephemeral (e.g. odors released only during specific periods of the day or night). Thus, olfactory cues can be manipulated over time and spatial scales that other sensory modalities cannot, and this is perhaps why we find an abundance of olfactory communication in the animal world. For adult moths, olfactory signals are a vital source of information that modulate many aspects of their behavior. In these animals, an appreciation of the features of odors coupled with behavioral experimentation has enhanced our understanding of the neurobiology of olfactory processing. KEY WORDS: olfaction, behavior, glomeruli, pheromone, flight Neil Vickers is an Assistant Professor in the Department of Biology at the Uni- versity of Utah. Tom Christensen is an Associate Research Scientist and John Hildebrand the Director and Regents’ Professor, both in the Arizona Re- search Laboratories Division of Neuro- biology at the University of Arizona. This article is a reflection of the au- thors’ diverse backgrounds and shared interest in understanding the neurobiological basis of naturally occurring behaviors. *Correspon- dence to: vickers@biology.utah.edu When we take a walk in the coun- try, the sensory modality that we tend to use to assess the environment is vi- sual. For many animals, however, olfac- tion is of far greater importance than vision in enhancing day-to-day survival. Odor adds an invisible dimension to a landscape, one that is rich in information for those organisms capable of sensing and responding to olfactory cues. In- deed, many animals rely to a greater or lesser extent on olfactory signals to gov- ern behaviors that allow location and identification of suitable mates or sources of food (plants, flowers, or prey). For social animals, odors can play a cru- cial role in the discrimination of kin from non-kin. Behaviors mediated by odor can involve complex orientation mecha- nisms and sometimes, learning and memory. These behaviors, when evoked in a relatively “clean” olfactory setting such as a laboratory, can be impressive. In a natural habitat, however, olfactory cues from a wide variety of different or competing sources may be present si- multaneously. Therefore, animals can be faced with a large amount of olfactory information at any particular instant, only some of which may be pertinent to the behavior currently being performed. How the chemical milieu is represented in an animal’s nervous system and how an organism deciphers and uses this in- formation to orient and navigate is a cur- rent subject of lively scientific inquiry. An integrative approach that links neu- roanatomy and neurophysiology within an ethological context, together with knowledge of the physical conditions that influence the distribution of odors in time and space is essential to our un- derstanding of how the detection of odor molecules is translated into com- plex behavioral responses. FEATURES OF ODOR SIGNALS To understand how odors are processed and represented by a sensory olfactory system, it is requisite to have some un- derstanding of the physical variables that can both affect the ability of a chemical to act as an odor and its distri- bution in the environment. A number of factors affect the release of a single chemical compound into a fluid me- dium (air or water), including its volatil- ity, the concentration of the chemical, the temperature and chemical compo- sition of the substrate from which mol- ecules of the chemical are diffusing, and