Why, then, are electronic atlases not more readily available today? Part of the answer appears to be that 1) until recently, working solutions had not been available with desk top computers for image acquisition and display at histological levels of resolution, 2) the drawing of structural boundaries by hand on a full set of brain sections was too labor-intensive, and automated segmentation was not yet feasible, given the relatively low-contrast inherent in stained sections of brain tissue, 3) use of electronic atlases that display the actual histological data sets was impractical because of limitations of memory and band width, and 4) individual differences in brain form imposed problems in defining a master ("canonical") brain for a given species. A fuller presentation of these and related issues is available in Toga AW, and Mazziotta JC. Brain Mapping: The Methods, San Diego: Academic Press, 1996, 420 pages.
Sufficient computer power is readily available now to resolve several of the problems summarized above. Certain further problems touched on above still persist for specimens as large and individually variable as the human brain, but have been solved here in our project on the mouse brain. We have bypassed the issue of individual variability by choosing a standard and widely used inbred strain of mice named the C57BL/6 strain. Differences between strains can be turned to advantage, and we predict that neuroscientists working with other inbred strains will take advantage of differences they encounter between their specimens and our "canonical" C57BL/6 mouse to explore the genetic basis for individual differences in brain organization. The mouse is generally recognized among biomedical scientists as a key mammal for research purposes, and is clearly the mammal of choice for the increasingly dominant field of genetic research. However, one may ask: is the mouse brain a good model for the human brain? The mouse brain is obviously much smaller and simpler, but it is of direct relevance with respect to human studies. The mouse brain contains the same array of basic components laid out in a more linear pattern, and serves very well as an introduction to mammalian brain architecture in general.