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Instructor

Ernesto Salcedo, Ph.D.


Ernesto Salcedo, Ph.D.

Instructor

B.S., Psychology
Duke University, 1993

Ph.D., Molecular Medicine
University of Texas Health Science Center San Antonio, 2001

Research Interest

Olfactory sensory coding using anatomical and behavioral techniques.                                             

Contact

Office Location: RC-1 South, Room 11123

Mailing Address:

Mail Stop 8108​
12801 East 17th Avenue
Aurora, CO 80045

Email: Ernesto Salcedo

The wiring of olfaction

Our sense of smell requires a surprisingly complex array of molecular machinery and neuronal networking. In fact, nearly one out of every one hundred genes in our genome are dedicated to producing the proteins that we use to physically detect the odorous volatile molecules (called odorants) that comprise smells. These proteins, known as odorant receptors, are expressed in olfactory sensory neurons (OSN) found lining the olfactory epithelium at the back of our noses. Each OSN expresses only one odorant receptor type and therefore has a restricted receptive field sensitive to a limited number odorants. From the olfactory epithelium, OSNs extend their single axons directly to the cerebrum into a structure known as the main olfactory bulb (MOB). Here, on the surface of the MOB, OSN axons are sorted into spherical neuropil called glomeruli, with each glomerulus accepting axons only from OSNs that expressm the same odor receptor type. Thus, the receptive field of a single glomerulus matches the receptive field of all of its incoming OSNs. In this fashion, each glomerulus serves as a single functional unit in an odor map of olfactory activity. For example, as shown the 2D odor map, glomeruli lining the ventral surface of the bulb (around 180˚) are relatively more responsive (warm colors) to the ethyl acetate odor than glomeruli in other regions of the bulb. Interestingly, due to their continuos exposure to airborne pollutants and other harmful materials, OSNs are necessarily replaced overtime. Their nascent replacements must then extend their single axon to a precise glomerular target on the MOB surface, often via tortuous routes that bypass hundreds of other glomeruli in the process.

My research interests focus on understanding how the odor map on the surface of the MOB is established and then maintained throughout the life of the animal. In addition, I am interested in understanding the role that these odor maps play in encoding olfactory information and how environmental factors may perturb the maintenance of this map and any subsequent encoding of olfactory information. For example, we have recently shown olfactory-dependent behavioral changes in animals when we introduced them into a new cage environment here at the AMC animal facility (Oliva et al, 2010). How the anatomical changes in the olfactory system that resulted from introducing these mice to these new cages resulted in these behavioral changes remains to be understood.

Towards these goals, we use the mouse as a model system. We have established a line of mice that coexpress a cellular marker (tau-GFP) with three different odorant receptors. In these mice, three different pairs of glomeruli, located in different regions of the bulb, are labeled with a fluorescent green. As the location of all glomeruli remain relatively constant throughout the life of an animal, we can use these labeled glomeruli as fiducial markers to better align odor maps between animals. Using the MATLAB computing language, we have developed a suite of software tools that has allowed us to map the location of any given glomerulus on the surface of the MOB to within biological variability. We are also able to map other structures, as well, including the laminar layers of the bulb. Using this software, we have developed a three-dimensional reconstruction of the mouse olfactory bulb (as seen 3D model of odor exposure to ethyl acetate) that allows us to better visualize odor maps and better compare maps between animals. Using immediate early genes, such as c-fos, we can also map the activity of glomeruli in response to different odors. By overlaying the position of the GFP-labeled glomeruli on these c-fos activity maps, we can begin to parse out whether any functional or behaviorally-relevant domains exist on the surface of MOB.


Salcedo, E., Zhang, C., Kronberg, E., & Restrepo, D. (2005). Analysis of training-induced changes in ethyl acetate odor maps using a new computational tool to map the glomerular layer of the olfactory bulb. Chemical Senses, 30(7), 615-26

Restrepo, D., Lin, W., Salcedo, E., Yamazaki, K., & Beauchamp, G. (2006). Odortypes and MHC peptides: Complementary chemosignals of MHC haplotype? Trends in Neurosciences.

Clevenger, A. C., Salcedo, E., Jones, K. R., & Restrepo, D. (2008). BDNF promoter-mediated {beta}-galactosidase expression in the olfactory epithelium and bulb. Chemical Senses, 33(6), 531-9.

Salcedo & Restrepo (2009). Major histompatibility complex. In ENCYCLOPEDIA OF NEUROSCIENCE. (pp. 2237-9). Berlin Heidelberg New York : Springer.

Restrepo, D., Doucette, W., Whitesell, J. D., McTavish, T. S., & Salcedo, E. (2009). From the top down: Flexible reading of a fragmented odor map. Trends in Neurosciences, 32(10), 525-31.

Oliva, A. M., Salcedo, E., Hellier, J. L., Ly, X., Koka, K., Tollin, D. J., et al. (2010). Toward a mouse neuroethology in the laboratory environment. Plos One, 5(6), e11359.

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