They did say Chloe has gray matter heterotopia (gray matter floating in her brain ).
Furthermore, when brain volume was corrected for the volume of tubers and subependymal nodules, gray-matter deficits were still apparent.
Then there is "Bucks on the Brain," which features a cross section of a man's head and several deer bounding through the gray matter.
The nerve cells themselves, with long branches (dendrites) that receive signals from other nerve cells, make up the gray matter that lies in a butterfly-shaped region in the center of the spinal cord.