Despite the tsunami of brain-related data being produced by laboratories around the world, we are in a crisis of ideas about what to do with all that data, about what it all means. I think that this reveals that the computer metaphor, which has served us so well for over half a century, may be reaching its limits, just as the idea of a brain as a telegraph system eventually exhausted its power in the nineteenth century
One of the most tragic indicators of our underlying uncertainty about the brain is the very real crisis in our understanding of mental health. From the 1950s, science and medicine embraced chemical approaches to treating mental illness. Billions of dollars have been spent developing drugs, but it is still not clear how, nor even if, many of these widely prescribed treatments work.
There have been many similar moments in the past, when brain researchers became uncertain about how to proceed. In the 1870s, with the waning of the telegraph metaphor, doubt rippled through brain science and many researchers concluded it might never be possible to explain the nature of consciousness. One hundred and fifty years later we still do not understand how consciousness emerges, but scientists are more confident that it will one day be possible to know, even if the challenges are enormous.
Virtually all we know from prehistory and history suggests that for most of our past we have viewed the heart, not the brain, as the fundamental organ of thought and feeling
The first recorded challenge to our global heart-centred view occurred in ancient Greece. In the space of about three and a half centuries, between 600 and 250 BCE, Greek philosophers shaped the way that the modern world views so many things, including the brain
Despite these insights, the earliest unambiguous statements about the centrality of the brain were written several decades after Alcmaeon died; they came from the school of medicine on the island of Kos, whose most famous member was Hippocrates
One of the most significant of these documents was On the Sacred Disease, which was written around 400 BCE
It ought to be generally known that the source of our pleasure merriment, laughter, and amusement, as of our grief, pain, anxiety, and tears, is none other than the brain. It is specially the organ which enables us to think, see, and hear, and to distinguish the ugly and the beautiful, the bad and the good, pleasant and unpleasant … It is the brain too which is the seat of madness and delirium, of the fears and frights which assail us, often by night, but sometimes even by day, it is there where lies the cause of insomnia and sleep-walking, of thoughts that will not come, forgotten duties, and eccentricities
Some people took the implications of localising epilepsy to the brain very seriously. Aretaeus the Cappadocian, a Greek physician who lived around 150 BCE, treated it by trepanation – drilling holes in the skull – a tradition that lived on in European medical manuals until the eighteenth century
Aretaeus did not invent this operation – the earliest traces of any medical intervention are holes that were drilled or scraped into people’s skulls and which can be found all over the planet, sometimes from over 10,000 years ago.14 Although it is tempting to view prehistoric trepanation as an early form of psychosurgery (it is often suggested that trepanation was performed to let out ‘evil spirits’), the global dominance of heart-centred ideas about the origins of thought suggests this is unlikely. There are more credible justifications for such a dangerous operation, including relief of painful subcranial bleeding or removal of bone fragments following a head injury.
It was another 400 years before decisive evidence about the role of the brain was obtained, through the work of one of the most influential thinkers in the history of Western civilisation: Galen. A Roman citizen, Galen was born in 129 CE to a wealthy family in the city of Pergamon in what is now western Turkey.18 Although today Galen is principally known as a writer on medical matters – his ideas shaped Western medicine and culture for 1,500 years – he was in fact one of the major thinkers of the late Roman world, producing millions of words of philosophy, poetry and prose
Despite the evidence that Galen presented, the authority of thinkers such as Aristotle and the power of everyday experience prevented brain-centred views from driving out the old ideas, even in Rome. Galen left an immense volume of work – around 400 treatises, of which over 170 survive, covering the whole range of medicine and natural science – but the decline and fall of the Roman Empire led to a collapse of the intellectual environment that could have permitted further discoveries. Simply thinking about where thought came from would never resolve the issue – as Galen’s work indicated, it would require anatomical and experimental investigation, which in turn could occur only in a context of intellectual openness and knowledge of past successes and failures through the circulation of ideas. Those conditions would not be repeated for centuries.
Haly Abbas also put forward an idea that was not present in Galen – he claimed that the three cavities or ventricles in the brain were full of animal spirits* that were created in the heart and transported in the blood. Each of the ventricles, he said, had a different psychological function: ‘Animal spirit in the anterior ventricles creates sensation and imagination, animal spirit in the middle ventricle becomes intellect or reason, and animal spirit transmitted to the posterior ventricle produces motion and memory.’ Despite the lack of evidence for this idea, it was widely held throughout Europe and the Middle East for over a millennium
It had first appeared in the writings of the fourth-century Bishop Nemesius of Emesa in Syria, and a few decades later was briefly mentioned by Saint Augustine, thereby acquiring a patina of religious approval that helped maintain its popularity.28 For over 1,200 years, ventricular localisation was widely accepted as self-evident – between the fourth and sixteenth centuries, at least twenty-four different versions were put forward.29 Among those who unquestioningly accepted this theory were some of the greatest thinkers of Europe and the Arab world, including Leonardo da Vinci, Roger Bacon, Thomas Aquinas, Averroes and Avicenna.
Readers of these newly available texts were well aware of the difference between the heart-centred view of Avicenna and Aristotle, the brain-oriented conceptions of the Salerno school and Galen, and the various attempts to reconcile them. In the thirteenth century, for example, Albertus Magnus squared the circle by simply arguing that Galen was wrong, and that all nerves did indeed have their origin in the heart, as Aristotle said.30 The modern response to such contradictory claims would be to make direct observations; the solution in the Middle Ages was scholastic and theoretical – thinkers tried to resolve the contrasting views of their revered predecessors by close textual analysis, not by experimentation.