History of the brain

The history of the brain details the development of thoughts, speculations, and ideas as to the function of the central nervous system, over the last five-thousand years.

Early views on the function of the brain, regarded it to be a form of “cranial stuffing” of sorts. In Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was regularly removed, for it was the heart that was assumed to be the seat of intelligence. According to Herodotus, during the first step of mummification: ‘The most perfect practice is to extract as much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with drugs.’ Over the next five-thousand years, this view came to be reversed; the brain is now known to be seat of intelligence, although colloquial variations of the former remain as in “memorizing something by heart”.

Early views
The Edwin Smith Surgical Papyrus, written in the 17th century BC, contains the earliest recorded reference to the brain. The word brain (adjacent), occurring eight times in this papyrus, describes the symptoms, diagnosis, and prognosis of two patients, wounded in the head, who had compound fractures of the skull.

During the second half of the first millennium BC, the Ancient Greeks developed differing views on the function of the brain. It is said that it was the pythagorean Alcmaeon of Croton (VI and V centuries BC) who first considered the brain to be the place where the mind was located. In the 4th cent. BC Hippocrates, believed the brain to be the seat of intelligence (based, among others before him, on Alcmeon's work). During the 4th century BC Aristotle thought that, while the heart was the seat of intelligence, the brain was a cooling mechanism for the blood. He reasoned that humans are more rational than the beasts because, among other reasons, they have a larger brain to cool their hot-bloodedness.

During the Hellenistic period, Herophilus of Calcedonia (c.335/330-280/250 BC) and Erasistratus of Ceos (c. 300-240 BC) made fundamental contributions not only to brain and nervous systems' anatomy and physiology, but to many other fields of the bio-sciences. Their works are now mostly lost, we know about their achievements due mostly to secondary sources. Some of their discoveries had to be re-discovered a millennia after their death.

During the Roman Empire, the Greek anatomist Galen dissected the brains of sheep, monkeys, dogs, swine, among other non-human mammals. He concluded that, as the cerebellum was more dense than the brain, it must control the muscles, while as the cerebrum was soft, it must be where the senses were processed. Galen further theorized that the brain functioned by movement of fluids through the ventricles.

Middle Ages
In the 10th century, Najab ud-din Muhammad first described a number of neurological disorders in detail, including agitated depression, neurosis, priapism, impotence, psychosis and mania. Haly Abbas described the neuroanatomy, neurobiology and neurophysiology of the brain and first described a number of other neurological disorders, including sleeping sickness, memory loss, hypochondriasis, coma, hot and cold meningitis, vertigo epilepsy, love sickness, and hemiplegia. Symptoms resembling schizophrenia were also reported in medieval Arabic medical literature.

In the 11th century, Alhazen, a founder of experimental psychology and psychophysics, pioneered the psychology of visual perception in his Book of Optics. He was the first scientist to argue that vision occurs in the brain, rather than the eyes, and pointed out that personal experience has an effect on what people see and how they see, and that vision and perception are subjective. Biruni, another pioneer in experimental psychology, was the first to describe the concept of reaction time. Avicenna was a pioneer of neuropsychiatry, and in The Canon of Medicine, he first described numerous neuropsychiatric conditions, including hallucination, insomnia, mania, nightmare, melancholia, dementia, epilepsy, paralysis, stroke, vertigo and tremor.

In al-Andalus, Abulcasis, the father of modern surgery, developed material and technical designs which are still used in neurosurgery. Avenzoar described meningitis, intracranial thrombophlebitis, mediastinal tumours and made contributions to modern neuropharmacology. Averroes suggested the existence of Parkinson's disease and attributed photoreceptor properties to the retina. Maimonides wrote about neuropsychiatric disorders and described rabies and belladonna intoxication. Elsewhere in medieval Europe, Vesalius (1514-1564) and René Descartes (1596-1650) also made several contributions to neuroscience.

Modern period
Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s that used a silver chromate salt to reveal the intricate structures of single neurons. His technique was used by Santiago Ramón y Cajal and led to the formation of the neuron doctrine, the hypothesis that the functional unit of the brain is the neuron. Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in 1906 for their extensive observations, descriptions and categorizations of neurons throughout the brain. The hypotheses of the neuron doctrine were supported by experiments following Galvani's pioneering work in the electrical excitability of muscles and neurons. In the late 19th century, DuBois-Reymond, Müller, and von Helmholtz showed neurons were electrically excitable and that their activity predictably affected the electrical state of adjacent neurons.

In parallel with this research, work with brain-damaged patients by Paul Broca suggested that certain regions of the brain were responsible for certain functions. This hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly deduced the organization of motor cortex by watching the progression of seizures through the body. Wernicke further developed the theory of the specialization of specific brain structures in language comprehension and production. Modern research still uses the Brodmann cytoarchitectonic (referring to study of cell structure) anatomical definitions from this era in continuing to show that distinct areas of the cortex are activated in the execution of specific tasks.