5

HOW BRAIN AND BODY TALK
TO EACH OTHER

I used to think that the brain was the most wonderful organ in my body. Then I realised who it was who was telling me this.

Emo Philips

To understand how intricately the brain is hooked up to the body, it is useful to have a rough overview of how the brain itself is organised. Luckily, Don Tucker, a psychology professor at the University of Oregon, has created just such a map of the whole brain in terms of its core functions. The map is three-dimensional. The dimensions are a bit rough and ready but they will help us see the wood for the trees. The first dimension runs (very broadly) from the largely sensory back of the brain (vision, hearing and touch are processed behind the so-called central sulcus: smell and taste are processed deeper down in the brain closer to the core) to the predominantly action-oriented front. Sensory information is arriving in the brain from many sources all at once, yet, on the behavioural level at least, we can only do one thing at a time so there is a progression along this dimension from multiple sources of information working in parallel to a more sequential, one thing at a time, organisation.

The second dimension differentiates the more routine- and habit-based left hemisphere from the more diffuse and creative right hemisphere. We have two hemispheres, it has been suggested, so that we can run two modes of attention simultaneously: one that is focused and analytical, the other that is more synoptic and holistic. Both of these modes are very useful, and each hemisphere can vary its degree of focus somewhat. But it gives us a big processing advantage to be able to have both modes running at once, and not having to segue between them.1

The third dimension, however, is the really important one for our discussion here. It runs from the innermost core of the brain, the brain stem, upwards through the structures of the limbic system to the outer ‘shell’ of the brain, the neocortex. This core-to-shell dimension carries information about needs and concerns – matters of personal significance – from the signalling systems of the body up into the outer regions of the brain where it is progressively integrated with information arriving through the senses, and also with the developing organisation of appropriate motor responses. And then messages are sent in the reverse direction, back down the chain to the brain’s core, whence the information can affect what is going on in the recesses of the body in the light of that centralised conversing and decision-making.

Moots and loops

Contrary to the Cartesian view, there is no big boss in the brain who forces through resolutions and dictates policy. According to the emerging perspectives of embodied cognition, the body is self-governing. It is like a medieval moot, a meeting that can reach a conclusion only by a process of respectful and attentive debate. A ‘moot point’ is one to which there is no easy or obvious answer and which therefore has to be referred to the moot. Much of the work of the body does have routine solutions, so no brain-based conversation is needed. But – especially in complex social worlds – moot points continually arise, and for these the central conclave is essential.

In Chapter 3 we saw some illustrations of how bits of the body talk directly to each other. But where information from muscles, guts, senses and glands has to be carefully coordinated in real time, the brain needs to be in the loop. And loops are what it needs. All the different bits of the body have information loops that run through the brain. The inward part of the loop from the ears or the stomach carries information about what is going on ‘out there’, and what needs or concerns there are ‘down there’. The ears might be saying, ‘Too loud, man’ (you might remember Stan Freberg’s version of the Banana Boat Song). The stomach might be saying, ‘I could murder a cheese sandwich’. The lymph glands in the neck might be saying, ‘Uh Oh, cold virus alert! Send us some more lymphocytes, willya?’ And looping back out from the brain are complementary channels that carry advice, information and resources in response.²

The anatomy and physiology of these loops is incredibly complicated and intricate and I am not going to attempt to do anything more than provide a few illustrations here. To recap, there are three kinds of information travelling around your body, chemical, electrical and physical. Electrical impulses, like those of an old-fashioned telephone system, run via the fibres of the autonomic and central nervous systems to and from the brain. They are rapid and can be very specifically targeted. The chemical messengers flow through the bloodstream and the lymph system, constantly coursing through the body, and can alter the signals that the nerves are sending. The chemical systems are slower than the electrical, though blood can travel from the heart or the gut to the brain in a second or two, so even ‘slower’ can be pretty quick in real time. And obviously the chemical systems are less accurately targeted: molecules and microorganisms have to float around until they happen to find a ‘lock’ to which they have the right ‘key’. This can be fine, if the distances the messages have to travel are small (perhaps from one side of a synapse to the other) or if a general broadcast is what is required (in an ‘all hands on deck’ kind of emergency). Having both forms of communication is clearly better than having either alone. In addition, many of these molecules are able to talk directly to the brain.

The third kind of whole-body communication, the physical, is often forgotten. But whole-body movements, as well as the continual ten-a-second waves of vibrations, carry information from here to there, and also help to coordinate activities in different areas of the body. For example, science confirms what we all know: that a walk after a large meal aids digestion. The gentle bumping and twisting of the whole body serves to massage and agitate the gut, which stimulates the release of digestive juices and stirs the contents of the stomach so that the juices can do their work more effectively. But movement plays a much more pervasive role than that. Coughing, sneezing, laughing and even yawning produce pressure waves in the body that (as well as squeezing the bladder) pump cerebrospinal fluid up to the brain, and increase blood flow, both of which change the concentrations of hormones and neurotransmitters that are swirling around the neurons and synapses. Orgasm and straining on the toilet may have analogous effects.3

Most organs, including the brain, are elastic and respond to whole-body movement with movements of their own. At the most gross level, a knockout blow to the head induces loss of consciousness, though why and how this happens is not yet known. At the micro level, every cell in the body is influenced by mechanical forces as the body and its different sub-systems twist and turn, tighten and relax, shake and tremble. Many functions of the cell – division, membrane permeability and gene expression, to name but three – are influenced by physical movement. In the brain, neurons physically twitch and turn when they are activated, and their axons propagate small pressure waves, as well as electrical and chemical ones. There are many protein molecules in the brain that both generate movement and respond to it. This small-scale physical activity may well affect the way messages are routed in the brain and the way neurons learn. A little is known about these mechanical effects, but this is a new field of research and a great deal remains to be discovered.4

Much of the chemical and physical information from the body is converted from changes in pressure, temperature, pulse rate or glucose concentration into electrical impulses within nerves, and these electrical messages, originating in the body, can simply be passed upwards, from synapse to synapse, to the brain. Pressure receptors in the walls of the arteries, for example, detect the physical ripples and distortions that occur with every heartbeat. The stretching stimulates electrical impulses that are carried up the vagus nerve and onwards into the brain stem, the mid-brain and thence to the neocortex. Feedback loops respond to the signals of increasing blood pressure – in the healthy body – by sending back messages that slow the next heartbeat and open up the capillaries to allow more blood through, thus lowering blood pressure and keeping it within safe bounds. Only a tiny fraction of this kind of activity is accompanied by any sort of awareness, and so we tend to neglect its significance – though it underpins much of the somatic intelligence on which we rely. That’s why chronically raised blood pressure is called ‘the silent killer’.

So information from muscles, bones, organs and skin travels via the brain stem to the ‘core’ of the brain, and then onwards to the outer layers of the neocortex. The loops pass through a series of way stations where their signals are processed and blended in different ways to extract different aspects of the information they are carrying. The deep core of the brain comprises a vast network of such processing plants, many of which have exotic, bewildering or rather appealing names. There is the parabrachial nucleus (with many arms like an octopus?), the nucleus of the solitary tract (a bit of a hermit?), the locus coeruleus and the nucleus accumbens (which sounds as if it is in need of a lie down). A particular favourite of mine is the periaqueductal gray, which I think ought to be an undistinguished water bird. Antonio Damasio is particularly keen on the superior colliculus (a rather self-satisfied small rodent, perhaps?). Then on they go to more familiar parts of the brain such as the amygdala and the hypothalamus. As the journey proceeds, so specific information originating from different parts of the body is combined to generate a more comprehensive picture.

Chemical communication

A good deal of this somatic information, however, is not converted into electrical impulses, but communicates directly with the brain. Despite the existence of the blood-brain barrier, which prevents many hostile bacteria and toxins from entering the brain directly, there are many areas in the brain that can and do pick up and respond to changes in the nature and concentration of the molecules floating by. Regions of the hypothalamus and the hippocampus, as well as the neocortex, respond directly to the concentrations of insulin and other insulin-like peptide molecules in their vicinity, for example, and this may change the neurotransmitters, such as dopamine, serotonin and noradrenaline, that are being released into different areas of the brain.

The insulin receptors are especially involved in regulating appetite, and in allocating energy resources around the brain. We know that changes to bodily concentrations of insulin will lead you to eat more or less, or to select different foods. More surprisingly, due to its direct action on the brain, insulin can also reduce your inclination to persist with difficult tasks. Staying focused on something you find hard and would rather not be doing is energetically expensive, so changes to insulin levels may have a direct impact on your willpower. This is worth emphasising, as it is a very clear illustration of the relationship between body and intelligence.

Other chemicals associated with the immune system are also intimately and continuously involved in allocating and distributing energy around the brain. They influence which bits of the brain get the most ‘juice’, and thus determine, amongst other things, how efficiently the synapses will work, and the rate at which connections are formed. When energy is low, thinking is harder and learning is slower. We all know that we shelve difficult tasks when we are under the weather, and just want to watch television or read magazines. But these influences of body on mind don’t just occur when we are ill; they are at it all the time.5

Our guts also talk to our brains via a host of chemicals. Peptides and hormones may be released from the walls of the gut in response to certain foods or the detection of toxins, and these, like insulin, travel to the brain and influence what it is doing. All you may be aware of is the desire for something sweet, or the need to visit the bathroom, but these conscious feelings and promptings are merely the gross result of a thousand small changes across the brain.

The gut is home to a collection of tiny creatures, the microbiota, so vast and so varied that they make Noah’s Ark look like a suburban bungalow. In your stomach, right now, there are ten times more microorganisms than there are cells in the whole of your body. Mostly we live in peace with this mass of tiny tenants, though, as we know, they sometimes get out of hand, and what is going on with their giant host can also upset them. Stress at any age, but especially early in life, may throw this symbiotic relationship out of kilter and stop the immune system working as well as it should, for example.

Yet we cannot function well without the microbiota. Their waste contains molecules (short-chain fatty acids) that are essential for our health. Animals that are raised in a totally sterile environment, where there is no chance for bacteria to colonise the gut, react abnormally to stress. Worse, germ-free mice have decreased levels of a hormone that is vital for the proper growth of nerves, for example in the hippocampus, and this leads to deficits in their ability to learn and to solve problems. More amazing still, germ-free mice that were colonised with microbiota from a different strain of mice started to behave more like the donor mice than like normal mice with their own DNA! If we are anything like the mice, we are biologically designed to live in harmony with our bacteria, and they shape our behaviour beneficially. So we should be careful with the antibiotics and the cleaning products.6

We should also be careful about how we are born. In a normal vaginal birth, bacteria begin to colonise the gut of the baby as it is travelling down the lower birth canal. Babies born by Caesarean section, however, miss out on this colonisation, and this has implications for their brain development. Caesarean-born babies have electrical brain activity that is less complex than babies delivered naturally. And rat pups born by Caesarean section show adverse differences, in the ways their brains develop, from those born normally.7

Small free-floating cells such as microglia and astrocytes are scattered throughout the brain, and these too are sensitive to changes in the concentrations of hormones and peptide molecules. If there is inflammation somewhere in the body, the brain quickly knows about it and responds, perhaps with a closing-down of perceptual interest in the outside world. Microglia and astrocytes may well be involved in altering the plasticity of the neurons, and in controlling the release and mopping up of neurotransmitters; they thus change our learning. Activated microglia release specific hormones that change the behaviour of other microglia across wide areas of the brain, thus magnifying any initial effect.⁸ In turn, organs like the pineal and pituitary glands can be instructed by the brain to secrete chemical messengers that will travel back to the provinces and regulate their activity.

All this research confirms the view that the brain is not just in the business of telling the body what to do. Bodily activity is influencing brain activity just as much as the other way round. Body and brain are tied together so intricately and so rapidly that it makes no sense to locate all the ‘intelligence’ in one and none in the other.

How the brain maps the body

Out of this maelstrom of physio-electro-chemical activity the brain creates a series of complementary maps of what is going on in the body. A good map is a useful distortion of reality; it picks out what is valuable, for a particular purpose, and chucks away the rest. The map of the London Underground is a really successful map precisely because it ignores almost everything about London, and misrepresents the remainder. (The distance between two stations bears scant relationship to their distance apart on the map.) So the brain extracts useful maps from the tumult of information it is being sent by every other part of the body: maps that can be read alongside each other to tell us what the best thing to do next might be.9

The nuclei in the lower and middle parts of the brain start out by mapping quite specific features of the body. Some make maps of the current position and state of tension of the limbs, or of the overall state of physical balance of the body. Some distil information about the state of the body’s different needs, for example on glucose levels, blood oxygenation, temperature and lactate levels in the muscles. Some record injuries and illnesses and draw out information that may surface into consciousness, after the maps have been redrawn a dozen times, as feelings of aches and pains or nausea. And some extract descriptions of the different kinds of touch that are occurring at the surface of the body: touches to the skin, to the lining of the nose, to the taste buds, to the tiny bones and muscles of the ears and the photosensitive skin, the retina, at the back of each eye. Temperature readings from various bodily locations can be summed and averaged to create an overall reading on the inner thermometer that triggers sweating or shivering, or makes us put on a sweater or head to the fridge for a cold beer.

By turning temperature and blood sugar and muscle tension into the common language of neural signals, different modalities can be integrated with each other to achieve higher-order mappings. The superior colliculus, for example, receives maps from the eyes, ears and skin, and begins to combine them into multimodal representations of objects in space.10 Other regions start to combine different sources within the body. Localised activities in the immune system – dealing with a paper cut to a finger, say, and feeling queasy from last night’s seafood buffet – get passed along and aggregated so that decisions of priority can be made. The sting of the cut may recede into the background as the feeling of nausea gets stronger. And finally, at the top of the loop, the portfolios of perceived opportunities, available actions and visceral concerns are mapped and put together, so that, if the phone rings or you are engrossed in a thrilling story, the ache in your backside from sitting so long on a hard chair goes unnoticed; or the stomach ache which had seemed so bad at breakfast magically dies down when you are told you don’t have to go to school.¹¹

Where it all comes together

Though these loops and maps are widely distributed round the brain and the body as a whole, there obviously needs to be a place where the high-level representatives of the body’s various systems, their ‘ambassadors’, so to say, can confer. And there are indeed two structures that play a pivotal role in integrating these sources of information: the insula and the cingulate cortex. The cingulate wraps around the large bundle of fibres called the corpus callosum that connects the two hemispheres of the brain and so is ideally placed to collect and redistribute information from a wide range of sources. (Cingulum means belt in Latin.)

The front part of the cingulate has been shown to have a special role in evaluating how what is happening at a sensory level relates to the signals of need or value coming up from the body, and especially in detecting when things are not going well. It is then involved in talking to the action planning parts of the brain, in order to adjust or design behaviour that might be both advantageous and appropriate. This bit of the brain has been called the ‘visceromotor cortex’ to emphasise its role in integrating perception with both the visceral needs of the body and the motor capacities which it uses to respond.12

The insula – which should really be called the peninsula, as it is not quite an ‘island’ – is connected to many parts of the brain, including the anterior part of the cingulate and areas of the pre-frontal cortex, by a host of functional causeways. It is about the size and shape of a prune, and each hemisphere of the brain has its own insula. Bud Craig, a researcher at the Barrow Neurological Institute in Phoenix, Arizona, has a good deal of evidence to back his claim that the posterior part of the insula creates an overall sense of how things are in the visceral parts of the body.¹³ Then, as patterns of neural firing are passed forward towards the front of the insula, this ‘primary interoceptive representation’, as Craig calls it, is integrated with other patterns coming from the muscles (‘proprioception’), from the predictions and expectations alive in the higher centres of the neocortex, and eventually from the outside world. All this culminates, in the anterior insula, in what he calls a ‘global emotional moment’: the composite background feeling of ‘how I am, right now’. It is the integrated sense which we refer to when someone says, ‘How are you?’ and we answer ‘lousy’, ‘a bit off colour’, ‘so-so’, ‘pretty chipper’ or, as my New Zealander friends are prone to say when feeling particularly well, ‘like a box of fluffy ducks, mate’.¹⁴ Psychology has long known that these moments integrate influences across a period of around a tenth of a second.

*****

Craig talks of these moments as if they were separate, like the frames of a film, but I prefer the image of a wave rolling through the ocean. On the gross level, the wave keeps its form, but the water – the content – keeps changing. At any ‘moment’ the wave represents the sum total of all the currents, swells and winds that are acting at that location. They come together to create a particular wave-form, with its signature composition and direction. Waves have a width; that is, they integrate the forces acting not at a point but over a small region of the ocean. The biological constraints on this span of integration might well account for the tenth-of-a-second duration of these apparent ‘moments’. But each momentary wave is not separated from the moment before and the moment after. Like a real wave, it has both a leading and a trailing edge. It is simultaneously rising, existing and fading. In the rising are expectations and predictions of what the future may bring, and in the fading are echoes of the confirmations and surprises that arose from moments that have just been. (So the fading edge is where learning happens.)

(We might, if we were feeling whimsical, see the properties of the seawater itself as the capabilities of the body to behave; the currents and groundswells as the values and concerns in play at that location in time and space; and the winds as the influences from the external world. Even more fancifully, we could imagine a wave on a phosphorescent sea at night, in which the glowing white crest of the wave, standing out against the sea, represents our conscious awareness. The tenth-of-a-second integrations might then correspond to the way this ocean would look if illuminated by a strobe. More on this line of thought in Chapter 6.)

We should remember that the sensory and motor maps are also interweaving, as information goes higher up in the brain, to create other maps that already imbue perception with the possibilities for action, and actions with the sensory consequences (marked as desirable or not) that might accompany or follow them. Sandra and Matthew Blakeslee summarise the research that shows how different areas of the brain cooperate in this way:

The sensory maps of your parietal lobe are also de facto motor centres, with massive direct interlinkage to the frontal motor system. They don’t simply pass information to the motor system, they participate directly in action. They actively transform vision, sound, touch, balance, and other sensory information into motor intentions and actual movements. And by the same token, the maps of the motor system play a fundamental role in interpreting the sensations from your body. Your parietal lobe is not purely sensory, and your frontal lobe is not purely motor. Physical sensation and action are best seen as a single sense that, like a coin, has two inseparable faces with different appearances.15

(emphasis added)

The work of the insula is all in the service of better – more fitting and effective – action. The more inclusive and well integrated is the information about current concerns, skilled capabilities and possible courses of action available in the world, the better the selection and design of behaviour will potentially be. Craig puts it more formally: ‘Cortical integration of high-resolution information on the state of the body provides improved conditions [to] guide behaviour ever more efficiently.’¹⁶ He argues that there is a clear evolutionary parallel, seen in different animals, between improved ability to select and control fluid responses and the development of this ‘high-resolution’ analysis of bodily states and needs in the insula. The anterior insula and the anterior cingulate are intimately interconnected, and almost always active at the same time. Together at the place where the various loops of information come together, the insula takes the lead on defining ‘what’s so’, and the cingulate leads on designing ‘what to do about what’s so’.

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Two further wrinkles to add before we leave the loops and maps.

First, you’ll recall that we touched earlier on the idea of ‘predictive coding’. The brain doesn’t create a replica image – a ‘Google Earth’, if you like – of everything that is going on in the world. That would be cumbersome and unnecessary. It creates guesses about what’s out there and only adjusts them if they are wrong. The same thinking has recently been applied to the brain’s representation of the body by Anil Seth, Hugo Critchley and their colleagues at the University of Sussex. The brain’s high-level maps generate guesses – based on all the expectations they have built up – about the kind of feeling we are having, what its significance might be, what might have caused it, and what we might be about to do about it. ‘I didn’t sleep well last night. I must be tired. So that feeling of ennui I’ve got (and those yawns I’m trying to stifle) are probably just exhaustion, not boredom …’ This guess is then relayed back into the body to see if it matches what is actually happening ‘down there’ (and to send back mismatch messages if it doesn’t). Such reasoning is not conscious or deliberate, of course – or not usually – but it is always part of the process whereby we come to experience what we are feeling.17 The brain does not need to build a replica ‘body’ inside itself – because it simply remembers where to go and look in the ‘real’ body if it needs to. Roboticist Rodney Brooks famously said, ‘The world is its own best model’.18 The same is true of the body. You only need to create models and maps for more subtle, distilled things that would not be self-evident in the body itself.¹⁹

The second wrinkle links to this. It comes from a suggestion by Damasio that the brain can create mini-loops (which he calls ‘as-if loops’) within itself to simulate the (wanted or unwanted) bodily effects of different perceptions and/or actions. Using the same high-level maps, the brain can run a simulation of what would (probably) happen in the body, if I did such-and-such, without actually having to engage the body directly – which would be more energetically expensive, as well as time-consuming. The brain takes its own guesses as to what is going on in the body (and what is causing it) for granted, and then proceeds to design actions on the basis of those conjectures. As I say, this saves time and energy – but it runs the risk that you may have got yourself wrong, in which case you will keep reacting to the present as if it were a rerun of the past when it isn’t.

Two ways of moving; two ways of perceiving

Our actions in the world are, broadly, of two kinds. There is action on the world, when we are at close quarters. I might pinch it, unwrap it, kick it, play it, fight it, drink from it, type on it or paint it. For this type of action, my body is the origin, the subject so to speak, and action emanates from this centre, so I need an egocentric map. From this perspective, ‘objects’ – such as an ‘audience’ or a ‘leg of lamb’ – are seen in terms of their affordances for beneficial manipulation. How I see them depends on what I am up to. In this frame, other things and other people are, as Hermann Hesse once put it, ‘cloudy mirrors of my own desire’.²⁰ There is the tight knitting together of perception, capability and my agenda that we have explored so far.

But there is also action that enables me to move through the world so I can get where I want or need to be. In this frame, my body itself is an ‘object’ that travels through space, so I need a map in which I can locate myself as one object amongst an array of others. This is called an allocentric map. This map is more ‘objective’: it is like a chessboard on which I am the White King surrounded by other pieces, some benign and some hostile. The other elements in this space still have relevance to me, but I am at one remove, and so more inclined to see in them a range of potential affordances rather than only the one that happens to be at the top of my list when I bump into them.

These two kinds of action – call them manipulation and locomotion – require us to operate in two rather different kinds of world, so it is no surprise that the brain has indeed evolved two such complementary systems. These have been well explored, especially in the context of vision – the sense, par excellence, that contributes to the feeling of being an entity travelling through space.

These two systems can be persuaded to reveal themselves, and their different priorities, with the aid of some simple visual illusions. In Figure 8, the central circle on the left definitely looks bigger than the one on the right, and no amount of measuring (which shows they are actually the same size) will change the way you consciously see it. But supposing these patterns are laid out as coins on the table in front of you, and you are asked to grab the middle ones: do your hands make the same mistake as your eyes and prepare a grip that is either too big or too small to grasp the coin? No, they don’t. If you are videoed as you reach out for the coins, and the recordings carefully analysed, you can see that your hand makes exactly the right grip to pick up the coins. The bit of the brain that is more concerned with immediate action than elaborated interpretation isn’t fooled by the illusion at all.21

Fig. 8 Titchener circles illusion.

The locomotion system, by contrast, takes, as I have suggested, a more objective, general-purpose view of things. It tries to detach its description of the world from immediate perspectives and give a more neutral view of what and where things are and how they might turn out. This Big Picture perspective often adds in assumptions that are generally true in 3D space. The figure on the left, stylised though it is, reminds the brain of looking down on top of a scene, in which the ring in the middle is nearer to you than the peripheral rings. The figure on the right looks to the locomotor system a bit like looking down a hole, in which the ring in the middle, if it were 3D, would be ‘further away’ and therefore looks smaller. The more ‘objective’ locomotor system can be tricked by the illusion, but the manipulation system doesn’t fall for it. If you are going to grab the central ring, you want to know how big it really is, not how big it is relative to its surroundings.

The manipulation system is evolutionarily older, and faster acting, than the locomotor system. (Think of a predator stealthily manoeuvring into position, and then pouncing.) It seems to be primed to make a quick assessment of ‘what’s out there’ based on size, shape and distance – the things you need to know if you are to make an effective grab for it, or a quick gesture of self-protection – and also a first guess at its desirability: is it worth grabbing for, or defending against? Moshe Bar says, ‘Like a Dutch artist from the sixteenth or seventeenth century, the brain uses … visual information to produce a rough sketch, and then begins to fill in the details using information from memory.’22 This initial sensory sketch flashes across the top surface of the brain, via what is called the dorsal route, and activates information in the orbito-frontal cortex, an area that is known to weigh up the value, relevance and utility of experiences. In the case of seeing a face, for example, the brain’s first sketch can tell the difference between a face and a non-face, and, crucially, can react differently to a happy as opposed to a sad face (and, a split second after that, breathing, heart rate and digestive processes are all beginning to be altered as well). Here we have another example of the way in which perception is almost instantaneously imbued with its relationship to our visceral concerns.

Cognitive control

As your body-brain is weighing up the situation it may well identify not just one but several courses of action that could be ‘the best thing to do next’. Many of your sub-systems are clamouring for attention, but your body has to act as a whole. The body is like a potentially unruly choir rehearsing for a concert. The choir is a cooperative, so everyone can have their say, but unless at some point we all agree on what we are going to sing, and in what order, the concert will be a shambles. We need some conducting – but the conductor is not a dictator, she is a coordinator, hired by the choir to help keep itself in line. And, at the same time as priority decisions are being made, the situation is often changing, so that you have to keep deciding whether to stick with the priorities you had a few seconds ago, or shift your focus of concern and explore new opportunities that may have just popped up. (New sheet music is constantly being published, so the potential repertoire is expanding.) Should you lock on to this, or take a peek at that? Your brain helps the body to synthesise, prioritise and sequence all these concerns and possibilities, and keep them under review. How does it do it?

Each of the possible courses of action under consideration gets tagged with a number of indicators that will help the brain to do its job of conducting the somatic orchestra. How important is it to achieve the goal of that action? How urgent is it? How much cost or effort will be involved in executing the plan? How risky is it: what could we lose if the plan fails or goes wrong? How likely is it to go wrong: how sure are we that we can ‘pull it off’? And how sure are we that the information on which the plan is based is reliable? These tags are what Antonio Damasio calls ‘somatic markers’, because they rely on information in and from the body. They involve estimations of value, significance, apprehension, confidence and risk, which are all emotional issues. And they are based on past experiences with similar actions in similar situations: experiences of relief, delight, doubt or disappointment. When an action (or an element of an action) becomes a live candidate in a new situation its somatic tags are activated, and they are looped through specialised parts of the pre-frontal cortex. These are designed to weigh up competing or conflicting claims of importance or legitimacy by a range of candidates, decide which is going to be the one that gets to steer the whole bus (for a while) – and stop the unsuccessful candidates from interfering!

Of course, there is no ‘little person in the brain’ who is making these decisions; the brain has to be organised so that a front-runner emerges automatically just by the application of some rules of thumb embodied in the way the neural networks function. These decision rules will determine how the activity in the different loops is added up and cancelled out. Whole books are written about how, in detail, this might be done, and which bits of the frontal lobes, coupled to which other bits of the brain, might be responsible for which operations. All I can do here is try to give a very rough sketch of the logic.

Remember that three sets of factors, each of them potentially complicated, have to be resolved together: the Needs, Deeds and See’ds. Sometimes the solution to this multivariate equation is clear-cut. There is an overwhelmingly urgent and important need (‘Stop the car, I’m going to be sick’ easily trumps ‘But we’re already half an hour late for dinner’). Or there is only one course of action open to me (‘No, Mr Bond; I expect you to die …’). But often the competition is more of a close-run thing, and then the relative strengths of the tags have to be taken into account and the knockout rounds begin. Important but not so urgent? You can go on the standby list. Important but uncertain of success, or too costly? Sorry, we can’t risk it at the moment.

The process is largely accomplished through the frontal lobes’ ability to deploy highly targeted bursts of neural inhibition across the rest of the brain. Especially important here are the dorsolateral areas of the prefrontal cortex – the top and side-facing portions of the frontal lobes on both sides of the brain. If one goal is becoming pre-eminent, the competing goals get actively suppressed and I experience a visceral clarity of purpose (a burning desire). If the choir decides that we need to stick with a single programme for the time being, attention to all those exciting new possibilities is dampened down and I become impervious to distractions. These shifting, strategic patterns of inhibition make some concerns stand in line and allow others to go ahead. They manage attention so that it becomes focused and selective (as opposed to broad, inclusive or distractible). They turn some sources of information up and others down (so we can swivel the spotlight of awareness from the rumblings in the stomach to the sound of the birds, and back to the words on the screen).

When the choice between candidates for action is tight, or when a good deal hangs on getting it right, inhibition can arrest the selection process so that potential consequences can be checked out more fully and possibly revised or relegated, and thus our responses appear more slowly or more ‘deliberately’. When these slower processes kick in, psychologists (who generally love to create binary oppositions) have often interpreted this as reflecting the activation of a different mental system, sometimes ingeniously referred to as ‘System Two’, that intervenes and restrains ‘System One’, a faster and more intuitive set of processes. But there is no need to parcel these processes up like this. Such bifurcations usually create more theoretical trouble than they resolve. I think it is only necessary to say that, under some (perceived) circumstances, the self-organising body-brain slows itself down.

There is an important corollary of this retardation. When inhibition stops an action flowing down into the muscles, or out into the lips and throat, it turns an overt action into an imagined action, or an actual utterance into a covert thought. And this, as we shall see in Chapter 8, creates the breeding conditions for both consciousness and creativity.²³

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So where is your brain? It is all over your body. And what is your brain? It is currents of information from all corners of your body continually making their way, by electrical, chemical or physical means, towards the stem of the brain, much of it by way of the spinal cord and the fluid canals of lymph and blood. Already subjected to some integration and simplification, each stream then moves up through various levels of the brain, being integrated with other streams of somatic information and transformed into a range of complementary ‘maps’ of the body’s states of readiness and need. As these high-level maps arrive at the neocortex they are further integrated with information arriving from all the special senses about the state of the outside world, and with more information about what types of action might be available and appropriate. In the anterior insula, the dorsolateral prefrontal cortex, the anterior cingulate and the premotor cortex, processes are applied to these representations that sort out competing priorities and decide on which action plans will go forward for full-scale implementation. If the stakes are high, other frontal lobe processes monitor the implementation to see if any unexpected glitches or unintended consequences are appearing, ready to slam on the brakes and ‘think’ again.

The job of deciding what to do next is often very complicated – but it is made somewhat easier by the installation in the body of some pre-set modes of reaction to particularly significant kinds of event. Installed by evolution, these various modes are what we now call our emotions. It is to these that we turn next.