Organization and Development of the Mammalian Visual System

Vivien Casagrande
Department of Cell Biology
T-2302 Medical Center North
615-343-4538 (office)
vivien.casagrande@Vanderbilt.Edu

The overall aim of Casagrande’s research program is to understand how visual information is processed in the brain and how nerve cells in the visual system become appropriately organized and connected during development.

The research is divided into two programs with separate aims. The first program is designed to understand the functional significance and structural correlates of proposed parallel information channels. Approaches include single unit recording including, pharmacological manipulation, light and electron microscopic examination of circuitry using tract tracing, immunocytochemisty and morphometry, optical imaging and neural modeling. In current experiments Casagrande’s students are using pharmacological tools to block or manipulate electrical signals in each pathway to determine how the visual system combines information within individual visual cortical cells. Experiments are also underway to examine differences in the circuitry and neurochemistry of layers and functional compartments in visual cortex using a combination of electron microscopy and immunocytochemical labeling for transmitters and transmitter receptors. Finally, collaborative experiments are underway that use optical imaging to examine functional organization in visual cortex.

The second program is designed to investigate how cellular patterns and connections of the adult nervous system are generated during embryo logical and early postnatal development. This program uses anatomical, immunocytochemical, surgical, and molecular biological tools to examine how axons find their targets and become topographically organized within the visual thalamus and cortex. Currently Casagrande’s lab has been investigating the earliest stages of axon ingrowth and connections between the lateral geniculate nucleus and primary visual cortex. Projects are underway that examine the function of glycoproteins and other extracellular matrix proteins in axon guidance in mice in which specific genes (i.e. either N-CAM or L1) have been deleted (knocked out). In vitro and in vivo studies are currently underway to examine axon guidance and cell migration in these models.