Christopher Walsh, MD, PhD, is chief of Genetics and a Howard Hughes Medical Institute Investigator at Children’s Hospital Boston, where his research focuses on genes that regulate the development and function of the human cerebral cortex. These genes are vital to normal development of the cortex, and many appear to have been altered evolutionarily to allow the unique aspects of the brain that underlie human cognitive abilities. Mutations in these genes are known to cause autism and epilepsy, as well as intellectual disabilities and other learning disorders.
In the second century, the Greek physician Galen proposed that the fluid in the brain provided energy for the entire body, theorizing that an external spirit (pneuma) from the lungs was transported to the heart, where, combined with blood, it would give rise to the vital spirit. Carried by the blood, the vital spirit was then thought to be transformed into an animal spirit before entering the cavities of the brain, then traveling through the nerves, “as sunshine passes through the air or water,” to energize the entire physical being.
In this view, the brain itself was a mere holder of the fluid. Our neuroanatomical term “thalamus,” referring to part of the brain stem, comes from the Greek word for “chamber,” implying that the brain was mainly important as a holder for CSF. The philosopher Descartes (1596-1650) thought that the brain was a pump that moved the fluid around to do the brain’s work, such as making a muscle contract. Seventeenth century Swedish scientist Emanuel Swedenborg referred to the CSF as a “spirituous lymph” and a “highly gifted juice.”