Adaptive processing in the insect olfactory system

Insects live in a complex olfactory environment containing thousands of volatile organic compounds (olfactory stimuli) at various intensities and mixture proportions, yet insects can detect and respond to specific olfactory stimuli at millisecond timescales. In this chapter, we describe the mechanisms by which the insect olfactory system can efficiently process an olfactory stimulus and how it filters the signal from background noise. Highlighting recent results from a variety of insect species, we consider: (1) the nature of the olfactory environment, (2) how olfactory information is filtered in the periphery, and (3) how the central nervous system efficiently and adaptively processes olfactory information. We propose that plasticity encoded in state- and learning-related processes allows the insect olfactory system to process and distinguish olfactory signals efficiently from background and to allow both the large-scale (e.g., meaning or value) and fine-scale (e.g., identity and composition) features of a stimulus to be encoded.