Monday, December 10, 2012
Computation and Neural Systems Seminar
Of Mice and Monkeys: A Journey into the Visual System
Edward Callaway, Professor, Systems Neurobiology Laboratories, Salk Institute
This talk will take a journey through studies of the monkey and mouse visual system that have been conducted in my lab over the last 17 years. I will first describe experiments that were aimed at understanding how local circuits in the monkey primary visual cortex integrate information from parallel input streams, and redistribute this information to extrastriate visual areas. These studies illustrate how difficult and tedious it has been using traditional methods to address detailed questions about how cortical microcircuits relate to visual function. I will then discuss studies demonstrating that cortical connections are cell type specific and that there are fine scale subcircuits embedded within cortical columns. These observations illustrate the need for a new generation of molecular and genetic tools that have been developed in recent years that allow studies linking neural circuits to function at the level of cell types and even single neurons. I will describe a rabies virus based mono-transsynaptic tracing system that has been developed in my lab that allows labeling of the direct presynaptic inputs to single neurons or specific cell types. This new generation of molecular and genetic tools can at present be used most powerfully in mice, where it is more straightforward to restrict gene expression to cell types than in monkeys. We are therefore both developing better tools for genetic targeting of cell types in monkeys and conducting studies of the organization and function of the mouse visual system. We have used intrinsic signal imaging and 2-photon calcium imaging to demonstrate functional retinotopic maps of extrastriate visual areas in the mouse and to functionally characterize the neurons in seven areas. These observations reveal both parallels and differences between the functional organization of extrastriate visual areas in mice and monkeys and lay the ground for future studies that allow the genetic tools in mice to be used to study how microcircuits mediate interactions between cortical areas and subcortical structures.