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Neural Coding of Sensory Information: Circuit Computations Underlying Fruit Fly Behavior
Summary: Vivek Jayaraman is interested in understanding how information from different senses is represented and integrated by ensembles of neurons in the brain. His lab plans to use a combination of experimental and computational techniques to explore multimodal circuits in the fruit fly brain. The lab's long-term goal is to link computation in such circuits to the insect's behavioral decisions.
We are constantly bombarded by the sights, sounds, and smells of the world around us. Many decisions we make are based, in some part, on the specifics of these sensory stimuli. For example, the visual appeal of beautiful scenery may keep us climbing up a tough hiking trail, but traffic noise from a nearby highway may be loud enough for us to decide it's not worth the effort. In a more mundane situation, we may choose whether or not to eat a particular fruit based on its color, smell, and feel.
A fundamental goal of sensory neuroscience is to understand how the brain represents and processes such information. Our research focuses on this issue, as well as on the question of how neural circuits integrate information from different modalities. We would like to uncover links between such computations and decision making. We believe that exploring such issues requires studying the activity of large populations of neurons in a behaving organism. Furthermore, validating any potential answers will require manipulating neural circuits in precise and well-controlled ways. A suitable model system to use is the fruit fly, Drosophila melanogaster, which has long been the organism of choice for behavioral genetics and comes with tools to fluorescently label, manipulate the activity of, and optically record from genetically targeted neurons.
Postdoctoral work done in recent years in Gilles Laurent's lab (California Institute of Technology) by Rachel Wilson (now at the Harvard Medical School) and Glenn Turner (presently at Caltech, soon to be at Cold Spring Harbor Labs) has made it possible to perform electrophysiological recordings from brain neurons in an intact adult fruit fly. We use an extension of this methodology to perform simultaneous electrophysiology and two-photon imaging in the intact fly. For optical imaging, we use recently developed genetically encoded sensors (of, for example, calcium). The advantage of such sensors is that the same genetically identified neurons can be targeted for imaging in fly after fly. Although these sensors currently lack the temporal resolution to monitor neural activity with high precision in vivo, they can nonetheless be used to identify foci of interest for more-refined recordings using electrophysiological techniques. With this combination of electrophysiological and optical methods, along with a variety of computational techniques, we are exploring the neural coding of sensory information in the fly brain.
Our lab is interested in two broad areas of research:
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Identification of neurons and circuits in the fly brain involved in multisensory integration: This effort involves using genetic, electrophysiological, and imaging techniques to establish functional connectivity and to map circuits of interest.
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Neural representation of sensory information: We will use existing electrophysiological and optical methods, as well as those in development, to study multimodal computations in single neurons and ensembles of neurons. Computational analysis and modeling are key components of this effort.
A major focus of our lab is to develop improved techniques for monitoring the activity of large numbers of neurons in an intact fly. Our goal is to be able to monitor and manipulate the activity of selected populations of neurons in a behaving fruit fly. In this effort, we will collaborate with labs at Janelia and elsewhere. To combine physiological recordings with fly behavior, we hope to work with Michael Reiser (JFRC) and to continue to collaborate with Glenn Turner. Much of the appeal of the fruit fly as a model organism lies in the many molecular tools being developed for it: expertise in this field will be available at Janelia through Gerry Rubin, Julie Simpson, and Loren Looger.
Establishing causal links between multimodal computations of neuronal ensembles and the fly's decision-making behavior is a long-term goal for our lab. Along the way, we hope to discover some general principles about sensory representations, neural computation, and the functional organization of small circuits in the fly brain.
Work to develop simultaneous electrophysiology and two-photon imaging in the intact fly was supported by grants from the National Institute on Deafness and Other Communication Disorders and the National Science Foundation to Gilles Laurent (Caltech), and a predoctoral fellowship from the Sloan-Swartz Center for Theoretical Neurobiology at Caltech (V.J.).
Last updated: September 14, 2007
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