Friday, January 29, 2010 - 12:15 p.m. Medium Conference Room

Emergent Complex Properties of the Mammalian Brain Clock

Rae Silver, Columbia University; and Duncan Foley, SFI External Professor and Graduate Faculty, New School for Social Research

Circadian oscillations based on similar molecular-genetic circuits  appear across a wide range of species, from single-celled prokaryotic  cyanobacteria to mammals. In mammals, circadian rhythms are governed by a  master clock located in the suprachiasmatic nucleus (SCN), with on the order of 10^4 neurons. Recent research reveals the SCN to be a complex organized system, which sustains circadian oscillations through the interaction of heterogeneous functionally differentiated sub-systems. Circadian rhythmicity was originally conceived as arising from weak coupling of individual cells.  Instead there is a characteristic spatial structure within the SCN indicating that individual cell oscillations are dependent on cell type and position within the SCN tissue. The frontier of research on the SCN is the effort to infer its neural network structure by synthesizing data from a variety of sources including dynamic optical imaging of living tissue slices in vitro, static images of tissue slices taken in vivo, and physiological and behavioral responses of living animals to manipulation of light and other environmental factors and genes and various internal factors. This aspect of SCN research intersects with related network inference problems such as food-webs, economic networks, epidemics, and knowledge diffusion. problemssuch as food-webs, economic networks, epidemics, and knowledge diffusion.

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