Accurate three-dimensional reconstruction of neuronal distributions in brain: reconstruction of the rat nucleus locus coeruleus.

A technique is described which permits construction of accurate, quantified 3-dimensional maps of the distribution of neuronal cell groups in brain. The cartesian coordinates of landmarks and individual neurons are obtained from serial histological sections utilizing a computer-linked digitizing microscope. The digitized images of these sections are displayed on a computer graphics picture system where they are aligned so that spatial relationships within the nucleus are essentially identical to those of the intact brain. This is accomplished using information about landmarks obtained from photomicrotomy. As a consequence of the alignment procedure, each neuron is assigned a 3-dimensional coordinate representing its position in the reconstituted nucleus, and the reconstruction is oriented in a stereotaxic coordinate system. Nuclei from different brains can then be registered to one another, assigned coordinates relative to this standard coordinate space, and be compared statistically. Differences between nuclei in the spatial distribution of neurons in toto, or in the distribution of anatomically or physiologically defined subpopulations of neurons, can then be visualized with greater accuracy and in more detail than that permitted by traditional techniques. In addition, such comparisons can easily be quantified and statistically evaluated using, for example, analysis-of-variance techniques. For illustrative purposes, the technique is applied to the rat nucleus locus coeruleus as reconstructed from serial Nissl-stained sections.