Function and plasticity of neural circuits in Drosophila

Our brains have no direct experience of the world. Rather, our perceptions are constructed from streams of action potentials, electrical signals carried by millions of nerve cells, which together form an internal representation of the external world.

How is information about the world broken into pieces and encoded in the simultaneous activities of millions of neurons? How are the pieces reassembled into a coherent picture? What are the cellular mechanisms underlying information coding, transfer, storage, and decoding? How are patterns of neural activity related to what we perceive? And how is information carried by neural ensembles read out and interpreted so as to inform behaviour?

To address these issues, we perform simultaneous genetic, physiological, and behavioural experiments on a model organism, the fruit fly. Specifically, we study olfaction, the fly?s sense of smell. When navigating their environment, insects rely heavily on odors: odors elicit complex behaviours of attraction and avoidance, feeding and courtship; odors are memorized and associated with other environmental cues, in ways that reflect an animal?s unique acquired knowledge of the world. The olfactory system mediating these functions is remarkably similar in structure to that of higher organisms, including our own, but it contains many fewer cells. Our goal is to understand, in mechanistic detail, how this relatively simple neural system ? comprising not more than 5,000 nerve cells, as compared to the many millions of cells in analogous vertebrate systems ? works.

How populations of neurons encode and process information, store memories, and control behaviour are central questions in neuroscience. We work on these problems by studying olfactory circuits and olfactory-driven behaviours in flies. Neither the organism nor the system is particular to our research goal, which is fundamental: we seek to discover general principles governing the operation of neural circuits, not the specifics of chemosensation in an insect.
In the recent past, we have developed and used two experimental strategies of genetically targeted imaging and control of neuronal activity to study how olfactory information flows from peripheral receptors to central brain structures, and how odour-driven behaviours are controlled. These two lines of research are now intersecting in a single group of neurons: the Kenyon cells (KCs) of the mushroom bodies. KCs sit midway between sensory and motor processes and may hold a key to understanding how the nervous system uses sensory information, combined with a record of past experience, to control future actions.

Our overall objective in this project is to determine how olfactory and neuromodulatory inputs regulate the physiology of KCs. Work on this system will allow us to explore two general principles of neural information processing: the role of ?noise? in signal transmission, and the organisation of associative memories.