  This paper describes an x-ray microtomographic technique for imaging the
three-dimensional structure of the human cerebral cortex. Neurons in the brain
constitute a neural circuit as a three-dimensional network. The brain tissue is
composed of light elements that give little contrast in a hard x-ray
transmission image. The contrast was enhanced by staining neural cells with
metal compounds. The obtained structure revealed the microarchitecture of the
gray and white matter regions of the frontal cortex, which is responsible for
the higher brain functions.
