What are brain ventricles, and what functions have been ascribed to them over the ages?

Brain ventricles are hollow, fluid-filled spaces within the brain that are part of the ventricular system. They are filled with cerebrospinal fluid (CSF), which serves several important functions, including cushioning the brain, maintaining intracranial pressure, and facilitating the circulation of nutrients and waste products.

Historically, the understanding of brain ventricles has evolved significantly:

1. Galen’s Theory: In the second century C.E., the Greek physician Galen proposed that the brain ventricles were crucial for the functioning of the brain. He believed that these cavities contained vital fluids (humors) that were responsible for sensations and movements. According to Galen, the movement of these humors to and from the ventricles via the nerves initiated sensations and motor functions 5.
2. Renaissance Views: During the Renaissance, anatomists like Andreas Vesalius provided detailed descriptions of the brain’s structure, including the ventricles. However, the ventricular theory of brain function persisted, with the belief that the ventricles played a central role in the brain’s operation, akin to a hydraulic system 5.
3. Seventeenth and Eighteenth Centuries: As scientific inquiry progressed, researchers began to focus more on the brain’s substance rather than just the ventricles. They recognized the distinction between gray matter and white matter, with white matter being associated with the transmission of information to and from the gray matter 6.
4. Modern Understanding: Today, while the ventricles are recognized for their role in producing and circulating cerebrospinal fluid, the focus has shifted to understanding the complex functions of different brain regions and how they interact. The ventricles are now seen as part of a larger system that supports brain function rather than being the primary site of sensory and motor control.