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Michael Leon

Professor, Neurobiology and Behavior
School of Biological Sciences

PH.D., University of Chicago, 1972

Phone: (949) 824-5343
Fax: (949) 824-2447
Email: mleon@uci.edu

University of California
2205 McGaugh Hall
Mail Code: 4550
Irvine, CA 92697

picture of Michael  Leon

Research
Interests
Olfactory coding
   
URL leonlab.bio.uci.edu
   
Research
Abstract
Our strategy to understand the olfactory code has involved four approaches. In the first approach, we determined whether the olfactory bulb encodes odorants in their entirety, or whether it encodes odorants by representing a combination of molecular features that together comprise a neural picture of each odorant. We found that at least some odorants are represented as a combination of odorant features that separately stimulate different regions of the olfactory bulb. Our second approach used odorants that differed greatly in molecular structure. We were able to identify molecular features, especially odorant functional groups that activate glomerular modules covering most of the olfactory bulb. Our third approach asked how odorants with very small differences in molecular structure are coded. We found evidence for chemotopic coding within modules where the centroid of activity within a module was determined by odorant length. Finally, we were able to predict odor perception from the neural representations of odorants that differed in only a single aspect of their structure. Specifically, enantiomers giving very different patterns of bulb activity could be spontaneously discriminated, whereas enantiomers yielding more similar patterns were not discriminated. By using these strategies, we have been able to learn some of the rules by which the code operates. We are now expanding our approach by significantly increasing the number of carefully selected odorants whose activity we map. This approach should allow us to evaluate specific hypotheses regarding olfactory coding lead to a better understanding of the means by which odorants are coded and also should allow us to establish an archive of odorant responses to relate olfactory neurobiology with odor perception.
   
Publications Effects of functional group position on spatial representations of aliphatic odorants in the rat olfactory bulb. Johnson BA, Farahbod H, Saber S, Leon M. J Comp Neurol. 2005, 483:192-204.
   
  Interactions between odorant functional group and hydrocarbon structure influence activity in glomerular response modules in the rat olfactory bulb. Johnson BA, Farahbod H, Leon M. J Comp Neurol. 2005, 483:205-216.
   
  Local and global chemotopic organization: general features of the glomerular representations of aliphatic odorants differing in carbon number. Johnson BA, Farahbod H, Xu Z, Saber S, Leon M. J Comp Neurol. 2004, 6:234-249.
   
  Spontaneous vs. reinforced olfactory discriminations., Linster C. Johnson, B.A., Morse, A., Yue, E. and Leon, M., Journal of Neuroscience, 2002, 22: 6842-6845
   
  Functional mapping of the rat olfactory bulb using diverse odorants reveals modular responses to functional groups and hydrocarbon structural features., Johnson, B.A., Ho, S., Xu, Z., Yihan, J.S., Yip, S., Hingco, E.E. and Leon, M., Journal of Comparative Neurology, 2002, 449: 180-194
   
  Perceptual correlates of neural representations evoked by odorant enantiomers., Linster, C., Johnson, B.A., Morse, A., Yue, E., Xu, Z., Hingco, E.E., Choi, Y., Choi, M., Messiha, A. and Leon, M, Journal of Neuroscience, 2001, 21: 9837-9843
   
  Expression of active caspase-3 in mitotic and postmitotic forebrain cells of rat., Yan, X.X, Najbauer, J., Woo, C.C., Dashtipour, K., Ribak, C.E. and Leon, M., Journal of Comparative Neurology, 2001, 433: 4-22
   
  Johnson, B. A. and Leon, M. Odorant molecular length:
One aspect of the olfactory code. Journal of
Comparative Neurology, 2000, 426, 330-338
   
  Johnson, B.A. and Leon, Modular glomerular
representations of odorants in the rat olfactory bulb and
the effects of stimulus concentration. Journal of
Comparative Neurology, 2000, 422, 496-509.
   
  Johnson, B.A., Woo, C.C., Hingco, E.E., Pham, K.L. and
Leon, M. Multidimensional chemotopic responses to
n-aliphatic acid odorants in the rat olfactory bulb.
Journal of Comparative Neurology, 1999, 409, 529-548.
   
  Johnson, B., Woo, C,C. and Leon, M. Spatial coding of
odorant features in the glomerular layer of the rat
olfactory bulb. Journal of Comparative Neurology,
1998, 393, 457-471.
   
Professional
Societies


   
Graduate Programs Neurobiology and Behavior

   
Research Center Center for Neurobiology of Learning and Memory
   
Link to this profile http://www.faculty.uci.edu/profile.cfm?faculty_id=2146
   
Last updated 08/18/2006