Sunday, 24 February 2013

The Little History of the Mind-Brain


My Brain, courtesy of the Wolfson Brain Imaging Centre. Thank you.

The Little History of the Mind-Brain

...in four thousand words, read it in about half-an-hour

I'm of the opinion that all that thinking and perceiving and decision-making, all that stuff which we call the 'mind', is something which is caused by the brain. I'm also of the opinion that if we could better understand how it works, then we'd be better able to solve a lot of the confusions, fears and dead-ends we humans are prone to. So here we go, the history of the mind and brain, squashed up as best I can...

That the brain causes the mind is so obvious these days that it hardly seems to need any explanation, let alone proof or defence. After all, don't we say 'use your head' when we mean 'do some thinking', or talk about an ingenious person as having 'a good head', or being 'brainy, and a daft one as 'soft in the head' ? But, even now, there are still large communities who will vigorously deny that the mind comes from the brain.
The essential feature of religion, the one thing which marks it out from other types of thinking, is its assertion that the mind does not arise from a solidly physical cause, but is, at least in part, a mystical material which can commune with the Almighty Power. Not all religions have a God, but every religion holds that some, or all, of the thinking and feeling we do and the personality we have proceeds from a spirit substance and not from the body to which it is only temporarily attached.
Though if the brain is just a sort of telegraph station between body and Soul, that doesn't explain why we big thinkers have such big brains, the brain of a vole would do fine.
But I don't think the religious view will do. The constant correlation between brain events and thought events means there isn't really any doubt that it is the solid, physical brain that causes the mind. So we must look at the brain to find the underlying basic system of the mind. But it is rather complicated - this bit-does that and that bit does, what?

The Ancient Egyptians

An ancient Egyptian's brain.
Actual evidence that it is the the brain which does thinking things goes back a long way. Something like three-and-a-half thousand years ago, around 1700BC, the Egyptian medical textbook now known as the 'Edwin Smith Papyrus' gives several examples of how injuries to the brain can alter intellectual abilities, for instance "If you treat a man for a fracture in his temple … you may call him, but he is dazed and does not speak to you". It says that he may cry tears and move his hands, but that, "this is an ailment for which nothing can be done", and, as if to prove to us that ancient scrolls are not necessarily unpolluted founts of wisdom, it goes on to suggest that you might relieve his symptoms by pouring milk in his ears.

The Greeks, the Psyche and the Pneuma

A thousand years later and the Greeks seem to have generally come to the idea that life and the stuff that goes with it, like thinking and feeling and reasoning, was caused by a 'life force' or 'psyche', from where we get our word 'psychology'. Sometimes 'psyche' gets translated as 'soul', which is very confusing, because its isn't like the modern idea of 'soul' at all. This was carried around by a fluid, known as the 'breath of life', or 'pneuma', though they weren't quite clear about which bits of the body did what with this supposed 'Vital Fluid'.

Pythagoras and Hippocrates

To Pythagoras, the mystical geometer, around 500BC, the heart expressed passion, while the brain did reasoning and intelligence. Interestingly, we know that when a comedian of the time, Cratinus, wanted to made fun of Pythagoras and his followers he described them as "Brain-bung'd".
The famous Greek physician Hippocrates, around 400BC, had no doubts: "Man ought to know that from the brain and the brain only arise our pleasures, joys, laughter and jests as well as our sorrows, pains, grief and tears ... It is the same thing that makes us mad or delirious, inspires us with dread and fear."
About the same time Plato of Athens seems to have thought that the brain, heart, liver and bowels all had their share in regulating the Vital Fluid, only the head "having more wisdom and sensation than the rest of the body"i. His pupil, Aristotle, taught that the brain was "one of the organs of sense" and one of "the main governing powers of life". But he was certain, perhaps from reports of head injuries where a person's brain had been exposed, that the brain wasn't the source of sensations "as it is itself utterly without feeling". Instead, Aristotle seems to have thought that the brain received and processed the Vital Fluid, keeping it at the right temperature, to stop us becoming 'hot-headed'. He also wrote a treatise on the nature of the psyche, though it's terribly rambling.

The discovery of different brain bits

A hundred year or so later and the school of Herophilos and Erasistratus, at Alexandria in the Greek bit of Egypt, actually dissected humans - some say while they were still alive - and noticed individual nerve fibres going to the brain, which they described as 'cords', 'ne͂v̱ron' in Greek, from where we get the word 'neuron'. They assumed, of course, that the neurons were tubes carrying the Vital Fluid to open pores - ventricles - in the brain. There's also a fascinating story about Erasistratus' wife, but there's no time for that here.

Most importantly, the Alexandrian Anatomists seem to have been the first to note that the brain isn't just one uniform organ. They made the distinction between the outer part of the brain, the pinkish wrinkly stuff - the 'Cerebrum' - and the separate smaller Little Brain or 'Cerebellum' at the back, and they saw that the inside of the brain, what is now vaguely called the Limbic System, is a collection of quite different and oddly-shaped objects all slotted together.
They saw that the whole neuronal system is connected, and hinted at a difference between the 'Voluntary' system of the limbs and the 'Involuntary' or 'Autonomic' system controlling everyday necessities like breathing and heart rate.
Four hundred years later the Alexandrian medical school still flourished, one of its pupils being Claudius Galen of Pergamon, who graduated to became the surgeon to a school of gladiators, and in 161AD moved to Rome to seek fame and fortune.

Galen tries hard

Galen didn't dissect humans, but tried to learn about them by cutting up their close relatives, apes and pigs. There he discovered that nerves run from the brain to the muscles and made the distinction we still use between the 'central' nervous system, inside the bones of the skull and backbone, and the 'peripheral system' in the limbs and and muscles. He went along with the idea that open spaces - ventricles - in the brain were where the Vital Fluid collected, and suggested that it was distributed through the 'Miraculous Net', (Rete Mirabile) a complex of tiny tubes under the brain. Unfortunately, that's the problem with experimenting on animals, the Rete Mirabile, we now know, is to do with regulating the temperature of blood - dogs have one in their necks and sea-birds have them in their legs, but humans don't have one at all. Galen's books were still being used in the Middle Ages.

The birth of 'Soul'

The ancients do seem to have thought that the Vital Spirit, the Psyche, was a physical thing, even if they weren't sure quite what. So where does the idea of a spirituous non-physical 'soul' come from? There's absolutely no mention of it, or of anything like it, anywhere in the Jewish or Christian Bible. It seems to be Tertullian, a Roman African, the 'Founder of Christian Theology', who came up with the idea. He said that "the soul is itself the spirit as day is the light", that it was "sprung from the breath of God, immortal, possessing body, having form, simple in its substance", it resided in the heart, was what controlled intellect and opinion and was the seat of divination and prophecy. Because the soul was immortal, it could be loosed from the body at death, with its self-knowledge intact, to be tortured in Hell if it so deserved. This grew into Church dogma, was taken up by the emerging Islam and seems to have seeped into other religions too.

Which bit does what?

The Extraction of the Stone of Madness.
Hieronymus Bosch c1494
Four hundred years into the Christian Era and Saint Nemesius of Emesa (that’s Homs in Syria), possibly on the basis of information from people with brain injuries, began what we might call 'brain mapping'; "The organ of memory is the hinder part of the brain and the Vital Fluid there contained … the senses have their sources and roots in the front ventricles of the brain, that those of the faculty of intellect are in the middle part of the brain."
Then there was Cenn Fáelad MacAilella, a 7th Century Irish scholar who is said to have suffered a head injury and, when he recovered, found he had a prodigious ability to recall information, the sort of thing which is now called 'eidetic memory', but which at the time was ascribed to his 'organ of forgetting' having been damaged, a not dissimilar idea to the concept of madness being caused by a stone in the brain.
Around 1000AD Al-Zahrawi of Al-Andalus in Spain described surgical treatments for neurological disorders. In 1504 Leonardo da Vinci tried squirting hot wax into the hollow brain ventricles of an ox to get casts of the place where those Vital Fluids collected. In 1564 Giulio Cesare Aranzi of Venice described the little curved organ inside the base of the brain, calling it 'hippocampus', from the Greek for seahorse, which it looks a bit like. A few years later Constanzo Varolio did some very detailed brain dissections and named the 'pons' or 'bridge', the knobby bit at the very top of the spinal column.

Descartes and the mind as machine

Descartes' diagram of nerve fibres
from his 'De Homine' of 1662
Another hundred years and the impressively polymathic René Descartes, following-on from some experiments with clockwork model creatures, was happy to describe the mind and body as "a machine". He claimed to have seen tiny strings inside the nerves which presumably could be pulled to alter the flow of the Vital Fluid in the brain with its organ of 'Common Sense' bringing all the impulse of the senses into one, common, place and so "make it capable of receiving the impressions of external objects". Descartes didn't want to go against the established Christian view, yet what was there left for the soul to do? His solution was to suggest that soul still did "Sense, the Imagination, and the Memory", but then communicated it to the brain through the pineal gland, a little organ right in the middle of the brain.

Enlightenment guesswork

Of course, if you fed the brain the wrong stuff, it wouldn't work properly, as when, in 1765, the Frenchman PJ. Grosley diagnosed the famous English melancholias; "The English live chiefly upon animal food. . . . Beef is their commonest sort of meat ... beer, their usual drink, must give rise to a chyle, whose viscous heaviness can transmit none but bilious and melancholy juices to the brain."
John Harris 'Technica' of 1765 knew that the brain "is the general Organ of Sense in which the Soul, the Governor of the Body, perceives and judgeth of the Sensations of all the sentient Parts and out of which as out of a Fountain it communicateth the Animal Spirits bred in the Brain by the Ducts and Rivulets the Nerves to all the sentient Parts of the Body and thereby endows them with the Faculty of performing animal Actions."
But how did it actually work? All very puzzling, as the Edinburgh anatomist Alexander Monro commented in 1763 "Some allege that the nervous fibres are all solid cords acting by elasticity or vibration, others maintain that those fibres are small pipes conveying liquors by means of which their effects are produced"

Electric discoveries

Then, in 1791, something quite unexpected happened. Luigi Galvani, a physician, was skinning a frog on a table where he had previously been conducting experiments with static electricity. His assistant touched an exposed nerve of the frog with a metal scalpel, they saw sparks and the dead frog's leg kick as if in life. This discovery began the realisation that animal movement was not necessarily caused by any Vital Fluid, but might have something to do with electricity.

Some people, quite a lot of people, went to so far as to assume that this 'Animal Electricity' was the Vital Fluid, the essential spark of life. Mary Shelley certainly took Galvani's book with her on the famous holiday during which she wrote 'Frankenstein', though it was later film-makers who decided that her monster would be recalled to life by electricity.
Galvani's nephew, Giovanni Aldini, made animal electricity into quite a career. He even had a go at poking electrodes into the body of a recently executed murderer at London's Newgate Prison, when; "the jaws of the deceased criminal began to quiver ... and one eye was actually opened."
But then, astonishment beyond astonishment, Alessandro Volta managed to produce electricity with no frog, corpse, or any other animal parts, but using a battery of metal and wet cardboard, "the nearest approach man has made to an experimental organism" said fellow physicist William Grove. It wasn't looking as if animals didn't need any mystical fluids at all.

The mind stops being magic

In 1819 Sir William Lawrence, Serjeant Surgeon to Queen Victoria and, funnily enough, Mary Shelley's family doctor, published a book of lectures he'd given alongside the wildly pro-Vitalist John Abernethy. Here he came straight out and said that the idea of a vital fluid was, "in opposition to the evidence of our senses and rational faculties", thinking and feeling was done by and in the brain alone. His employers, and the Lord Chancellor, disagreed and required him to recant this 'blasphemy' and suppress the book. Just 200 years ago, and you could be censured by government for suggesting that the mind was caused by the brain
Then in 1828 Friedrich Wöhler managed to synthesise an organic substance, urea, as he put it "without the use of kidneys, either man or dog". It had been thought that organic compounds could only be produced in living things, so this pretty well put paid to the Vitalist idea of life being dependent on a mystic fluid.
But whatever it was that nerve fibres carried, it had been assumed that they carried it along almost instantly. Or perhaps at the speed of electricity, which is about a quarter of a million kilometres per second. But in 1850, Hermann von Helmholtz managed to measure the speed of nerve impulse, it is very slow indeed, only about 70 metres per second, about one four-millionth of the speed of electricity. So whatever a nerve fibre is, it isn't an electric cable.

Feeling the bumps

About the same time Franz Joseph Gall began going around Austria promoting his 'Cranioscopy'. This was the idea that different bits of brain did different things, and bigger bits would do that thing more, so you could identify personality by looking at the shape of someone's skull. An idea which succeeded in being denounced both by the scientific establishment for lack of evidence, and by the Church for whom the idea that the mind should have a physical seat in brain matter was a monstrous heresy.
Nonetheless, measuring the bumps on your head developed quite a vogue, especially as 'Phrenology' with those handsome porcelain heads marked with maps including 'locus of fortitude', 'seat of mirth' and so on. There was yet more twitty nonsense like this gem from Gall's Scottish follower George Combe: "the head of a Christian is broad behind, and flatted out at the crown; that a Mahomedan's head grows narrow at the top, and, like a monkey's, has a conic form", which provided a handy canvas for racists.
By the 1900's Phrenology still commanded a certain intrigue, as Joseph Conrad tells in his novel 'Heart of Darkness'. The hero is having a medical exam before going off to the deeply dangerous African colonies when the old doctor; "with a certain eagerness asked me whether I would let him measure my head. Rather surprised, I said Yes, when he produced a thing like callipers and got the dimensions back and front and every way, taking notes carefully ...  'Ever any madness in your family?' he asked, in a matter-of-fact tone."

The callipers could be bought for the purpose, and there was even a semi-automated skull measuring machine. But these theories were rubbish, they did not match actual observations. Yet, just like the Alchemists of the Middle Ages whose forlorn attempts to make gold accidentally gave rise to the science of chemistry, so Cranioscopy and Phrenology opened up a general acceptance of the idea that the mind is caused by the brain and that different bits of brain do different stuff. What was needed was evidence from the real world.

Broca's discovery

It was in 1861 that the prodigiously clever French physician Paul Broca had conducted a post-mortem on a M. Leborgne, a patient at the Bicêtre Asylum who suffered from just the sort of 'expressive aphasia' the old Egyptian had noted - he could comprehend spoken language and try to reply using hand signs, but the only word he could speak was "tan". Broca found a lesion in the frontal lobe of the cortex of his brain, just behind the left temple, a correlation he went on to confirm in more than a dozen other cases. This bit of brain is now called 'Broca's Area' and is known to be associated with the articulation of language.
Broca's own brain is now in the Musée de l'Homme in Paris, not far from a cast of the skull of another former guest of the Bicêtre, the aristocrat of pornographers, the Marquis de Sade. The Marquis' head was purloined by Johann Spurzheim, a Phrenology pioneer and former partner of Franz Joseph Gall, who wanted to know how its owner's notorious kinkiness related to the shape of his head.

Wernicke's observations

Not long after Broca, the Prussian Carl Wernicke studied the brain of a patient who had suffered a stroke which left him with the opposite speech problem to Monsieur "tan". Wernicke's patient was able to speak, and his hearing was fine, but he could barely understand language at all, either spoken or written. Wernicke found damage to an area, now named after him, just behind the skull above your left ear, which is associated with language reception. He went on to begin a complete map of the brain and its actions, but was killed in a cycling accident before he could finish it.

Golgi and Cajal - brain cells start to come clear

Sketches made by  Santiago Ramón y Cajal
LEFT:Growth of a simple neuron   RIGHT: Purkinje neurons (pigeon)
Which bits of brain did what was becoming evident, but not how the thing worked inside. Then, around 1843, Camillo Golgi developed the reazione nera, the "black reaction", a way of staining brain tissue using silver so that the brain's millions upon millions of individual nerve fibres - neurones - could be seen for the first time. This allowed the sometime science-fiction writer 'Doctor Bacteria', under his real name of Santiago Ramón y Cajal and in his day job as a pathology researcher at the University of Barcelona, through years of painstaking observations cataloguing the many and various types of neuron to establish the fact that, while nerones are all sorts of different shapes and sizes, they all have the same basic structure  - a thick 'soma' in the middle with thin dendrites and axons. The dendrites listened for signals from neighbouring neurons, while the axons were the transmitters.
The Golgi stain gave a clear image of individual neurones because it only stained a few here and there. Strangely, the stain didn't seep from one to the next, leading to the remarkable conclusion, now part of what is called the 'Neuronal Doctrine', that neurones aren't actually connected one to the other. There appears to always be a tiny space, called the 'Synaptic Gap', between the  branching ends of one neuron and the beginning of the next.
Golgi and Ramón y Cajal shared the 1906 Nobel Prize for their discoveries, Golgi's home village in the Alps was renamed Córteno Golgi in his honour while Ramón y Cajal got an asteroid named after him.

Mr Gage, Mr Molaison and other odd characters.

Mr Gage with spike
At this point in stories of neuroscience, a small cast of characters usually enters, famous for having got parts of their brains altered, which then altered their ways of thinking. There's Phineas Gage, an American railway engineer who accidentally got a steel spike knocked right through the middle of his brain, supposedly damaging bits of his limbic system and making him grumpy. Then there's Henry Molaison, whose surgeon removed his hippocampus in a desperate attempt to cure his epilepsy, it worked, but lost him his ability to make new memories. The mysterious JW and VP both had a bit across the middle front of their brain, the corpus callosum, severed and developed very odd understandings of left and right. Unfortunately, these tales have grown in the telling. None of them are quite as simple as they are often presented. So we won't bother with them here.

Hodgkin, Huxley and the Giant Squid

In 1952 Alan Hodgkin and Andrew Huxley, using the relatively big and easy-to-see neuron from a Giant Squid, finally found what it is that travels through neuronal fibres. It isn't a mystic breath, or a fluid. Nor do the nerve fibres work by being pulled like strings. It turns out not to be a substance at all, but a wave, or pulse, of alteration in the concentration of sodium ions, a travelling 'action potential'.
Hodgkin and Huxley's diagram of
electical potentials in the neuron

It can only travel in one direction along the neuron and it is rather slow. It can't actually cross the 'synaptic gaps' between the end of one neuron and the start of the next - instead it causes the 'axon' end bits to release neurotransmitter chemicals, which float over the gap and induce a new potential on the 'dendrite' on the other side. (In the process of which, the neurotransmitter chemicals can also float around and affect nearby neuron-ends). It isn't an electrical system at all, except inasmuch as pretty much everything is 'electric', when you look closely enough. Hodgkin and Huxley got Nobel Prizes, though they didn't get anything named after them, as far as I'm aware.

Inside the living brain

A 'false-colour' X-Ray

Then, of course, starting with X-rays about 1880, ways were invented of sort-of looking-at what was inside the living brain, which I'll leave you to look them up yourself at http://en.wikipedia.org/wiki/Brain_scan . They confirm, as the Egyptian found out, that particular bits of brain do particular things. Unfortunately, they also conform that most of the interesting things that the brain does involve many different pieces of tissue working together. The brain is a richly interconnected system riddled with feedbacks, with loops and with puzzling dead-ends. Saying that emotion is in the amygdala, or that decision-making is the prefrontal cortex, is at best no more than a very rough shorthand. Comprehending a sentence, say, probably involves Broca’s area, but it also draws in other parts of the temporal lobe, the sensorimotor cortex and the basal ganglia. Nothing is ever just in one spot. It is in many, among which the least active may well be the most significant. To add to the fun of which, there seems to be a degree of plasticity involved - particular bits can sometimes alter their functions, as when blind people seem to use parts of their visual cortex for other sensory purposes or when a stoke patient learns to 'think round' the damaged part of their own brain.

Libet's Spanner

Oh yes, and in 1964 Benjamin Libet from California threw a bit of a spanner into the works by carrying out some experiments to try and discover how the 'feeling' of wanting to do something related to actually doing it. Subjects were asked to stop an electronic clock at a moment of their choice, and also to note the moment when they first decided to go ahead and stop the clock. Their brain scans seemed to show that a 'readiness potential' for the 'stop' intention first arose in the brain, well before subjects themselves were aware of it. Which either suggests that consciousness is the result not the cause of things and that the brain does things very differently to the way it tell us it is doing, or that Mr Libet's experiments were a bit muddled. Or all of those.

So, there you go, that's the Little History Of The Mind-Brain.
Now, have I missed anything out, and how are we going to make sense of that lot?