Use of Computers for Quantitative, Three-Dimensional Analysis of Dendritic Trees

Publisher Summary This chapter describes the use of a computer-microscope system to quantify the three-dimensional structure of single neurons from whole mounts of cortical slices and also discusses the labeling procedures that are necessary prerequisites to this type of analysis. The approach can be divided into three essential techniques. Slices of brain tissue are maintained in vitro and neurons are labeled by intracellular dye injection. The thick (400 μm) slices are processed as whole mounts. Then an entire dendritic tree is encoded in three dimensions directly from a whole mount. The resulting data file consists of a series of three-dimensional coordinates that specify the exact branching pattern of the tree. It includes information on dendrite diameters, branch points, and termination points and can be used to calculate parameters such as individual branch lengths or the total dendritic length of the neuron. Alternatively, the data file can be entered directly into a simulation program and used to build an electrotonic model of the dendritic tree. The above approach is applicable to neurons from any region of the mammalian brain, although it was developed originally to analyze the dendritic trees of neurons in the hippocampal formation of young adult rats.