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Many of the most interesting functions and behaviors realized by the brain emerge from the collective activity of very large numbers of neurons of many functional types interacting in complex networks. Our long-term goal  to establish the principles underlying the structural and functional organization of such circuits in the brain.  We hope to understand how large-scale behaviors can emerge from the interaction of many individual elements, what the constraints on neural circuit architecture are, and in what ways network functions can be impaired or improved by changes to the architecture.  We exploit theoretical and computational approaches from physics, statistics and computer science, and rely on experimental data gathered both within our lab and by collaborators at Penn and elsewhere.
 
Current experimental work in the group explores the adaptation of networks of neurons in the retina to stimulus statistics. Many of our physiological studies are based on multi-electrode array recordings (see below for a clip of a spike from a retinal ganglion cell captured on a 30-electrode array). We have developed a simple, scalable and efficient new algorithm for sorting spikes recorded by such arrays.
 
Ongoing theoretical work concerns the organization of cortical maps in various areas of the brain, the application of Bayesian statistics to decision making in the brain, and the organization of various systems that support vision, olfaction and spatial cognition. We also apply information theory and techniques developed in neuroscience for data analysis and for understanding of network function to analogous problems in the study of signaling and regulatory networks in cells.
 
Some of our efforts are guided by the hypothesis that biological systems are adapted to the statistical structure of the stimuli that they encounter in their environments. This hypothesis can generate testable predictions if such statistical structure can be measured reliably. For our work on the retina we have therefore gathered a large, calibrated database of natural images, available from this site. For details about a particular research topic please select from the menu above.