Digital image reconstruction for the study of brain structure and function.

Functional activity of brain can be defined as the change in physiological activity that accompanies change in behavior. Although the precise relationship between such coupled activity is still being explored, autoradiographic methods for measuring brain blood flow, metabolism and receptor ligand densities have advanced to the point where it is possible to survey the entire brain of an animal for such changes. These developments offer the opportunity for studying brain as a whole--that is, for surveying the entire brain to identify the sites where changes in blood flow, metabolism or receptor chemistry occur with a particular behavior. The development of computer-based image analysis systems offer the possibility for visualizing such holistic brain function. We identified 4 steps which must be accomplished in developing a three-dimensional (3D) display for studying brain function. This paper describes the development and implementation of procedures for these 4 steps. Sectioning and digitizing representative tissue (e.g. autoradiograms, histology, histochemistry) with an adequate sampling frequency. Alignment and reconstruction of the components which make up the whole brain so that the original shape and orientation prior to sectioning is maintained. Projection and surface generation of a 3D model where the shading of the surface is mathematically dependent on the location of light source(s) and the viewer. Localization and quantification of planar cuts through the 3D model. Density data which reference the original autoradiograms are displayed along the exposed surface of the designated plane. The final presentation of data once these 4 steps are completed allows for the identification and visualization of changes in functional activity within the whole brain.