Learning from Insect Brains: CNS Processing of Behaviorally Significant Odors

Abstract

We seek to understand neurobiological mechanisms through which information about behaviorally significant olfactory stimuli is encoded, processed, and integrated with inputs of other modalities in the CNS and specifically how olfactory information controls natural behavioral responses. We study the antennal lobes (ALs), the primary olfactory centers in the brain of the giant sphinx moth Manduca sexta. As in olfactory bulbs of vertebrates, the ALs are characterized by glomeruli – condensed‐neuropil structures in which primary‐sensory and central neural elements interact synaptically. Insights from our prior work on the moth's sex‐pheromonal communication system led to recent analysis of olfaction‐dependent interactions with host plants. A multidisciplinary approach combining chemical characterization of natural volatiles, behavioral experiments in a laboratory wind tunnel, and electrophysiology has enabled us to determine how mixtures of volatiles, at natural concentrations, control source‐seeking behavior and are encoded in the ALs. Mounting evidence points to coincident firing of glomerular output neurons as a mechanism for neural coding of the context or significance of a behaviorally ‘meaningful’ odor. (This research has been supported by NIH grant R01 DC002751.)