Visualization of density relations in large-scale neural networks

The topological organization of interfacing neuronal populations in the bas al forebrain of rats was investigated in 3D by using computational methods for extracting information about the spatial distribution of cell densities and density relations. We claim that numerical and spatial constraints imp osed by these methods may help to define neuronal clusters in this brain ar ea where simple two-dimensional histology failed to reveal such an arrangem ent. Neuronal clusters have been suggested in many brain regions as sites o f integrative operations. Taking advantage of computerized data acquisition methods in the 3D reconstruction of large cell populations we introduced f our basic methods to visualize density relations on simple and combined cel l markers: Differential Density 3D Scatter Plot, Iso-relational Scatter plo t, Iso-density Surface Rendering and Iso-relational Surface Rendering. Thes e methods are described and exemplified on a 3D neuronal database acquired from mapping different chemically or hodologically defined cell populations in serial sections of the rat basal forebrain.