Medieval and Islamic Brain Science

From the 'cell doctrine' that housed imagination, reason and memory in the brain's ventricles to Ibn al-Haytham's optics and Ibn Sina's medicine — how ideas about the brain were preserved and extended between antiquity and the Renaissance.

After the fall of the Western Roman Empire, much of Greek medicine survived through translation into Syriac and Arabic, and later back into Latin. Ideas about the brain in this period centred on its hollow chambers — the ventricles.

The cell doctrine

Building on Galen and on early Christian writers such as Nemesius (4th century), medieval scholars developed the cell doctrine: the mind's faculties lived in the ventricles, arranged front to back. The front cell held the sensus communis (where the senses combine) and imagination, the middle cell reasoning, and the rear cell memory. Diagrams of a head with three bubbles appear in manuscripts and early printed books for centuries. It was an early theory of localisation — wrong in its details but right that different functions might live in different places.

The Islamic golden age

Physicians in the Islamic world translated, criticised and extended Greek medicine. Al-Razi (Rhazes, c. 865–925) wrote detailed clinical descriptions, including of head injury. Ibn Sina (Avicenna, 980–1037) wrote the Canon of Medicine, used as a standard textbook in Europe and the Middle East for some six hundred years, which discussed disorders such as meningitis, stroke and what we would now call mental illness. Al-Zahrawi (Abulcasis) described surgical treatments for head and spinal injuries.

Ibn al-Haytham and vision

The most enduring contribution came from Ibn al-Haytham (Alhazen, c. 965 – c. 1040). His Book of Optics argued, with experiments, that we see because light from objects enters the eye — not because the eye sends out rays, as many Greeks believed — and that perception involves judgement and inference by the mind. That idea, that the brain actively interprets the senses, sounds strikingly modern.