Nathan N. Urban Associate Professor Ph.D., University of Pittsburgh Postdoctoral Appointment, Max-Planck Institut fur medizinische Forschung nurban@cmu.edu Laboratory Website 412-268-5122 (Phone) 412-268-7129 (Fax) 173 Mellon Institute Department of Biological Sciences Carnegie Mellon University 4400 Fifth Avenue Pittsburgh, PA 15213

My long-term research interests center around understanding the physiological mechanisms underlying the functional and computational properties brain neuronal networks. These mechanisms are best elucidated by detailed studies of the physiological properties of the synapses, cells and circuits involved in the performance of a given task. In particular, I am interested in how phenomena such as dendritic integration and synaptic plasticity may allow small groups of neurons to perform complex functions. Understanding such computational properties of brain networks often requires the simultaneous acquisition of data from several cells within a network and/or from multiple locations within a single cell. Thus, I also am interested in the application and development of physiological and optical techniques that facilitate this sort of parallel data acquisition in vitro and in vivo.

My current interests center on understanding how the circuitry of the olfactory bulb transforms the spatially segregated, rate-coded and combinatorial glomerular odor representation, into a representation that is more spatially homogenous, more sparse and which may depend on the precise timing of mitral cell spikes. In particular I want to understand how this transformation is implemented in the circuitry of the bulb. One prevailing idea is that the circuitry of the olfactory bulb is functionally similar to the circuitry found in the retina and in parts of the neocortex in that it performs a kind of "lateral inhibition". On this view activation of a given mitral cell should result in inhibition of neighboring mitral cells. However, unlike visual stimuli, olfactory stimuli are not intrinsically spatial in nature. Moreover, it is not clear that similar odors are mapped onto nearby regions of the bulb which makes it difficult to understand how lateral inhibition is implemented by bulb circuitry.

Recently, I have been working to describe the lateral spread of inhibition and excitation within the network of the mitral and tufted cells, which are the output neurons of the olfactory bulb. Whole cell and optical recordings from mitral cell dendrites have allowed me to examine activity-dependent short term changes in recurrent and lateral inhibition that might underlie variations in odor-evoked activity that we observe on the time scale of seconds. I have described how these processes underlie the competitive interactions between mitral cells and how they shape odor representations at the level of the olfactory bulb.

Selected Publications

Castro JB Urban NN. Subthreshold Glutamate Release from Mitral Cell Dendrites. J. Neurosci;29(21):7023-30, 2009 May 27.

Ermentrout GB, Galán RF, Urban NN. Reliability, synchrony and noise. Trends Neurosci; 31(8):428-34, 2008 Aug.

Arevian AC, Kapoor V and Urban NN. Dynamic Gating of Lateral inhibition in the Olfactory Bulb. Nature Neuroscience; 11(1):80-7, 2008 Jan.

Galán, R.F, Ermentrout GB, Urban NN. Optimal time scale for spike-time reliability: Theory, simulations and experiments.  J Neurophysiol; 99(1):277-83, 2008.

Ermentrout GB, Galán RF and Urban NN. Relating neural dynamics to neural coding. Physical Review Letters. Physical Review Letters; 99. 248103, 2007.  Faculty of 1000 Must Read.

Bagley J, LaRocca G, Jimenez DA and Urban NN. Adult neurogenesis and specific replacement of interneuron subtypes in the mouse main olfactory bulb. BMC Neuroscience; 8(1):92, 2007.

Kapoor V and Urban NN. Glomerulus-specific, long latency activity in the olfactory bulb granule-cell network. J. Neuroscience; 26(45):11709-19, 2006. Faculty of 1,00 Recommended.