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The NUIN Student Sponsored Seminar Series presents

Ed Callaway, PhD

Professor,
Systems Neurobiology Laboratories
The Salk Institute for Biological Studies, La Jolla, CA

on Friday April 25th at 4:15 pm

Hughes Auditorium, CH

Unraveling fine-scale and cell-type specificity of cortical circuits

Abstract:

We have found that cortical circuits are extremely precise, such that different neuron types, and even neighboring neurons of the same type, are connected differently. For example, different types of inhibitory neurons with overlapping dendritic arbors receive connections from different cortical layers.  And neighboring excitatory neurons only receive common input from the same presynaptic neurons in the minority of cases when they are directly connected to each other.  This fine-scale and cell type-specific organization implies that studies of relationships between circuits and function should match this level of organization. This is a difficult challenge requiring the development of novel experimental methods. To test hypotheses about contributions of specific cell types to neuronal responses and to perception, we have developed methods to allow reversible inactivation of selected cell types.  We find that expression of an insect neuropeptide receptor which couples to GIRK channels can be used to selectively, quickly, and reversibly eliminate the activity of neurons in vivo.  This method allows tests of the role of particular cell types within the intact, functioning neural network.  To allow more precise assays of neural connectivity we have developed a recombinant, pseudotyped rabies virus that allows the neurons directly presynaptic to a single neuron or to a genetically targeted population to be specifically labeled.  This method is compatible with expression of any gene of interest in the presynaptic neurons, for example, expression of genetically encoded activity sensors. This should allow the precise circuitry of specific neurons to be more directly linked to function.

Bio:

Ed Callaway is a professor in the Systems Neurobiology Laboratories at the Salk Institute for Biological Studies. He received a B.S. in Biology from Stanford University in 1984 and a Ph.D. in Biology from the California Institute of Technology in 1988.  Work in his laboratory is aimed at understanding how neural circuits give rise to perception and behavior. Studies focus primarily on the organization and function of neural circuits in the visual cortex. Relating neural circuits to function in the visual system, where correlations between neural activity and perception can be directly tested, provides fundamental insight into the basic mechanisms by which cortical circuits mediate perception.

Selected publications:

1. Dantzker, J.L. & E.M. Callaway (2000) Laminar sources of synaptic input to cortical inhibitory interneurons and pyramidal neurons. Nature Neurosci. 7, 701-707.
2. Yabuta, N.H., Sawatari, A. & E.M. Callaway (2001) Two functional channels from primary visual cortex to dorsal visual cortical areas.  Science 292, 297-300.
3. Chatterjee, S. & E.M. Callaway (2003) Parallel Color-Opponent Pathways to Primary Visual Cortex. Nature 426, 668-671.
4. Yoshimura, Y. & E.M. Callaway (2005) Fine-Scale Specificity of Cortical Networks Depends on Inhibitory Cell Type and Connectivity. Nature Neurosci. 8, 1552-1559.
5. Yoshimura, Y., Dantzker, J.L. & E.M. Callaway (2005) Excitatory Cortical Neurons Form Fine-Scale Functional Networks. Nature 433, 868-873.
6. Nassi, J.J.*, Lyon, D.C.* & E.M. Callaway (2006) The Parvocellular LGN Provides a Robust Disynaptic Input to the Visual Motion Area MT. Neuron 50, 319-327. *Co-first authors.
7. Nassi, J.J & E.M. Callaway (2006) Multiple Circuits Relaying Primate Parallel Visual Pathways to Area MT J. Neurosci. 26, 12789-12798.
8. Tan, E.M., Yamaguchi, Y., Horwitz, G.D., Gosgnach, S., Lein, E.S., Goulding, M., Albright, T.D. & E.M. Callaway (2006) Selective and Quickly Reversible Inactivation of Mammalian Neurons in Vivo Using the Drosophila Allatostatin Receptor. Neuron 51, 157-170.
9. Wickersham, I., Lyon, D.C., Barnard, R.J.O., Mori, T., Finke, S.,  Conzelmann, K.-K., Young, J.A.T. & E. M. Callaway (2007) Monosynaptic Restriction of Transsynaptic Tracing from Single, Genetically Targeted Neurons. Neuron. 53, 639-647.