Kathryn Hamilton, Ph.D.
Associate Professor
Department of Cellular Biology and Anatomy
Ph.D., 1980, University of California, Santa Barbara

Major Research Interests:
Our goal is to determine how synaptic interactions of external plexiform layer (EPL) interneurons with mitral and tufted (M/T) output cells contribute to the odor encoding functions of the olfactory bulb. This structure is the first processing center in olfaction. It is a layered structure, making it readily amenable to electrophysiological and anatomical studies of network computations performed by different cell types during olfactory processing. The EPL is the second cellular and synaptic layer of processing, and its network computations are thought to play a key role in regulating M/T cell activity. Using patch recording and biocytin labeling methods, we have found that mouse EPL interneurons exhibit several subsets of electrophysiological and morphological properties and that in two dimensions they bridge areas below pairs of adjacent glomeruli, which receive the olfactory sensory input from the nose. The spontaneous activity and evoked responses of the interneurons are consistent with anatomical studies suggesting they are excited by and inhibit different M/T cell subtypes within different portions of the EPL. Our results also show that the interneurons receive inhibitory synaptic inputs. We are testing the hypothesis that EPL interneurons include several electrophysiologically, morphologically, and/or neurochemically distinct subtypes that have different spatial domains within the EPL, where they are excited by different subtypes of M/T cells and inhibit each other. These studies will provide important new information about the contributions of EPL interneurons to the spatiotemporal encoding of odor information in the olfactory bulb.

EPL interneuron and recording of its spontaneous activity (Hamilton et al., 2005).

Selected Recent Publications:
Journal articles
Allen, D.M. and K.A. Hamilton (2000) Ultrastructural identification of synapses between mitral/tufted cell dendrites. Brain Res. 860:170–173

Du, J., R.E. Maloney and K.A. Hamilton (2002) Video-microscopic analysis of dye coupling in the salamander olfactory bulb. J. Neurosci. Res. 68:385–397.

Hamilton, K.A. and D. Coppola. (2003) GluR1 distribution is altered in the olfactory bulb following narisocclusion. J Neurobiol. 54:326–333

Hamilton K.A., Heinbockel T., Ennis M, Szabó G, Erdélyi F, Hayar A (2005) Properties of external layer interneurons in mouse olfactory bulb slices. Neuroscience 133:819-829.

Heinbockel T., K.A. Hamilton, and M. Ennis (2007) Group I metabotropic glutamate Receptors are differentially expressed by two populations of olfactory bulb granule cells. J. Neurophysiol. 97:3136-3141.

Hamilton, K.A, S. Parrish-Aungst, F.L. Margolis, F. Erdélyi, G. Szabó, and A.C. Puche (2008) Sensory deafferentation transsynaptically alters neuronal GluR1 expression in the external plexiform layer of the adult mouse main olfactory bulb. Chem. Sens. (in press).

Book chapters
Ennis, M., Hamilton, K.A., and Hayar, A (2007) Neurochemistry of the main olfactory system. In Handbook of Neurochemistry and Molecular Neurobiology, 3/e, A. Lajtha (ed.-in-chief), Vol. 20, Sensory Neurochemistry, D. Johnson (ed).

Contact Info:
Kathryn Hamilton, Ph.D.
Associate Professor
Department of Cellular Biology and Anatomy
LSU Health Science Center
Shreveport, LA 71103
Tel: (318) 675-5391
KHamil@lsuhsc.edu