Charlene Ong
St. Louis, Missouri, United States

Western medicine’s understanding of neuroanatomy over the last several millennia has reflected the dynamic cultural values and social norms regarding the human body and its function. The journey that culminated in accurate and reproducible representations of the brain required a tolerance of human inquiry, advances in preservation technology, and skilled artistry. The transition from the theological and theoretical schema that characterized the medieval period to the empiricism espoused by the Renaissance and Enlightenment provided the necessary environment for a more precise understanding of neuroanatomy and pathophysiology.

While Herophilus and Erasistratus in 270 and 260 BC are considered the first to document their study of the human brain,¹ it was Galen of Pergamon’s work two hundred years later that proved to be the most enduring. Because human dissection at that time was often criminalized, most of his work was limited to animals.² His adoption by the Church four centuries later as the indubitable anatomist of antiquity led to lasting misinterpretations of the brain’s structure and function.

Galen theorized that intellect was composed of three elements: imagination, reason, and memory. He localized these three functions to what he called the first, second, and third “cells” of the brain, corresponding to the lateral, third, and fourth ventricles.³ We now know that the ventricles house the cerebrospinal fluid that surrounds the brain and have no intellectual, motor, or sensory function. This doctrine was widely disseminated as the official position of the Church in the 4^th and 5^th centuries⁴ and remained uncontested until the reintroduction of human dissection in the late 13^th century.⁵ Representations of the brain were not meant to be realistic, but rather to schematically reflect the “Cell doctrine.” (Fig 1)

Over the course of the Renaissance, the human body became a study of interest for social and artistic purposes, providing the necessary cultural climate for further study. Anatomists slowly transitioned toward a more realistic view of the brain. However because the longstanding prevailing theory of brain function designated the parenchyma largely irrelevant, less effort was put forth toward precise and accurate depictions of the gyri and sulci. Engravings in the 13^th and 14^th centuries depicted the brain in situ, half exposed in the cranial vault complete with facial expressions of the owners.⁶

Andreas Vesalius is credited with the creation of the first modern anatomical atlas, De Fabrica, in 1543.⁷ He procured a large volume of subject material, suggesting that: “Heads of beheaded men are the most suitable [for dissection] since they can be obtained immediately after execution with the friendly help of judges and prefects.”⁸

Immediate access to the recently deceased was particularly important given the brain’s speedy decomposition. Because of his efforts, Vesalius’ anatomical study was more comprehensive than that of any of his predecessors. However his depictions of neuroanatomy were not entirely complete. He omitted cerebral vascular structures and continued to inaccurately render gyri, reflecting the continued underestimation of their relevance and function. Most notably, his early works continued to include the rete mirabile, a network of vessels at the base of the brain found in hoofed mammals described by Galen and mistakenly attributed to human anatomy.⁹ The sanctification of Galen’s teachings led to the continued portrayal of this non-existent structure in publications and textbooks far after experience and examination should have disproven the mistake.

Thomas Willis’ Cerebri Anatome built upon the foundation provided by Vesalius a century earlier in 1664. Unlike the majority of his predecessors, Willis and his colleagues approached the brain from below, removing it from the skull before slicing it from the base upwards.¹⁰ The technique allowed for closer examination of complete specimens, avoiding the resultant tissue breakdown that Vesalius and his contemporaries battled while working within the cranial cavity. Willis’ compatriot, Christopher Wren, later known for his architectural achievements, devised a method of injecting contrast in the vasculature to better delineate vessels, further preserving the brain’s original shape.¹¹ His engravings relayed both a realistic representation of the brain and emphasized significant anatomic locations based upon a newfound understanding of neurologic function.

These advances resulted in unprecedented accuracy of neuro-representation. All cranial nerves were depicted for the first time. New structures were identified, including the anterior commissure, cerebellar peduncles, claustrum, corpus striatum, inferior olives, internal capsule, medullary pyramids, optic thalamus, spinal accessory nerve, and stria terminalis.¹² Willis’ detailed study of these structures, in conjunction with his extensive comparative studies of birds, fish, and mammals, led him to suggest a radical retort to the “Cell doctrine.” He proposed a complete perspective reversal highlighting the parenchyma as the source of the brain’s function with three new areas of significance: the corpus striatum, the corpus callosum, and the cerebral cortex,¹³ laying the foundation for our modern understanding of neuroanatomy.

Note

*About the image: This is an 11^th century drawing of the skull facing inward and seen from above with coronal, sagittal and lambdoid suture represented by double lines. Mental faculties are labeled as “fantasia” (imagination), “intellects” (reasoning) and “memoir” (memory). The brain itself is labeled cold and moist, consistent with the Ancient Greek theory of qualities ascribed to organs. (Clarke E, Dewhurst K. An Illustrated History of Brain Function: Imaging the Brain from Antiquity to the Present, 2^nd ed. San Francisco: Normal Publishing, 1996. p. 9)

References

1. Tascioglu AO, Tascioglu AB. Ventricular anatomy: illustrations and concepts from antiquity to Renaissance. Neuroanatomy 2005;4:57.
2. Ibid.
3. Clarke E, Dewhurst K. An Illustrated History of Brain Function: Imaging the Brain from Antiquity to the Present, 2^nd ed. San Francisco: Normal Publishing, 1996;8.
4. Ibid.
5. Cavalcanti DD, Feindel W, Goodrich JT, et al. Anatomy, technology, art, and culture: toward a realistic perspective of the brain. Neurosurgical Focus 2009;27(3):1
6. Cavalcanti DD, Feindel W, Goodrich JT, et al. Anatomy, technology, art, and culture: toward a realistic perspective of the brain. Neurosurgical Focus 2009;27(3):2
7. Singer C. Brain dissection before Vesalius. Journal of History Med Allied Sciences 1956;11(3):262.
8. Ibid, 268.
9. Cavalcanti DD, Feindel W, Goodrich JT, et al. Anatomy, technology, art, and culture: toward a realistic perspective of the brain. Neurosurgical Focus 2009;27(3):5
10. O’Connor JPB. Thomas Willis and the background to Cerebri Anatome. Journal of the Royal Society of Medicine 2003;96(3):141.
11. Feindel W. (ed.) Thomas Willis. The anatomy of the brain and nerves. Tercentenary edn. Vol 1 Introduction; Vol. 2 Facsimile. Montreal: McGill University Press;1965:24.
12. Molnar Z. Thomas Willis (1621–1675) the founder of clinical neuroscience. Nature Reviews Neuroscience. 2004;5(4):333.
13. Molnar Z. Thomas Willis (1621–1675) the founder of clinical neuroscience. Nature Reviews Neuroscience. 2004;5(4):334.