Experience-dependent modulation of olfactory representations and behavior in Drosophila

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We are all born into a world full of visual, auditory, tactile, gustatory and olfactory stimuli, but not everyone grows up in the same stimulus environment. For example, a child who grows up next to a bakery wakes up to the smell of fresh bread every day, while his friend who lives next to a flower shop is welcomed by the fragrance of flowers whenever he comes home. Do such childhood experiences affect the sense of smell and odor preferences of an adult? Animal studies suggest that this is indeed the case. Neural plasticity during early life allows the nervous system to adapt to the environment that the animal is born into. These neural adaptations in turn shape the animals’ behavior in adulthood: early experience with a stimulus can alter the preference for that stimulus, and it can improve the animals’ ability to detect and recognize it. We have basic knowledge about how the peripheral nervous system is altered by early stimulus experience. However technological challenges have largely prevented us from gaining deep understandings of the effects on higher brain regions, especially of mammals. As a consequence, little is known about how plasticity in the peripheral nervous system translates into changes in animal behavior. Fortunately, effects of early stimulus exposure can be observed not only in mammals, but also in some insects including the fruit fly Drosophila. Drosophila is an excellent model system for studying the phenomenon of early stimulus exposure induced plasticity in the context of olfaction for three reasons: First of all, both peripheral neurons in the olfactory circuit and odor-driven behaviors are modulated by odor pre-exposure during early life in Drosophila. Secondly, we are now in possession of new techniques which enable us to capture the complete neuronal representation of an odor with single cell resolution in a higher brain structure that is involved in driving olfactory behaviors. Lastly, we have tools that allow us to analyze the behavior of individual flies towards an odor in great detail. Thus, experience-dependent changes in neural odor encoding can be related to changes in aspects of olfactory behaviors. Understanding the neuronal basis for behavioral changes due to early odor experience in Drosophila will reveal principles of early experience encoding that may be shared between insects and humans.