Michelangelo was a religious man, but he was also a scientist. He must have been very conflicted about painting a brain and brainstem in God's head and neck, especially in the Sistine Chapel. After all, he was commissioned by the Church, which did not take too kindly to literal images on its murals.
But, paint the brain he did, even if it was just an outline of the brain in the section of the Sistine Chapel depiction of the Creation of Adam.
Michaelangelo's painting of the Creation of Adam in the Sistine Chapel: First identified by Meshberger in 1990.
Recently, two Johns Hopkins University neurologists did further study of Sistine Chapel frescoes and found more anatomical depictions in the fourth panel of the series The Separation of Light From Darkness.
The fourth panel, showing God in the 'Separation of Light From Darkness' depicts a ventrel view of the brainstem: images by authors Ian Suk and Rafael Tamargo, via Neurosurgery
Being a student of anatomy and having dissected bodies from the age of 17 until old age, Michelangelo must have been driven by great exuberance about his anatomic discoveries to include them in the Sistine frescoes. Ian Suk, and Rafael Tamargo, the researchers from Johns Hopkins, theorize as much, and assume that probably the rest of Michelangelo's anatomical drawings were discarded for fear that they would become known by the Church, who paid his salary most of his life.
Suk and Tamargo present very convincing evidence that, though the brain and brain stem are camouflaged, Michelangelo was really attempting to teach - first by alluding to God using his brain to create Adam and then, a year later, to include the brain stem so obviously in the Separation of Light and Darkness. Was Michelangelo suggesting that it is the brain that separates light from darkness?
The authors provide plenty of evidence for their theories. Look, for example, at the portraits of the other characters in Separation of Light From Darkness. They are all turned in the same direction as God, but only God has the brain. Further, Suk and Tamargo show how strange it is that God's beard is not flowing, but rolled up. For the purpose of revealing the brain?
God's beard is even rolled up so his brain stem will be visable, or is it obvious?: images by authors Ian Suk and Rafael Tamargo, via Neurosurgery
The Concealed Neuroanatomy in Michelangelo's Separation of Light From Darkness in the Sistine Chapel, published in Neurosurgery is fascinating if you are interested in the history of art, the history of science, and/or the history of the Church.
Neurosurgery, Medical News Today, NPR.com