CHAPTER THREE
The machine that constructs reality
How does consciousness emerge in the brain and how are we governed by our unconscious?
It is now possible to read and explore our thoughts by decoding patterns of brain activity. With this we can begin to establish, for example, whether a vegetative patient is aware or not. We can also explore dreams and resolve whether they actually happened as we remember them, or are just a narrative created by our brain as we woke up. Who wakes up when consciousness is awoken? What happens in that precise moment?
Consciousness, like time and space, is something we all are familiar with but have trouble defining. We feel it and we sense it in others, but it is almost impossible to define what it is made of. It is so elusive that many of us often fall into different forms of dualism, evoking a non-physical and non-spatial entity to represent the conscious mind.
Lavoisier, the heat of consciousness
On 8 May 1794, in Paris, one of the finest of French scientists was guillotined by Maximilien Robespierre’s troops after being accused of treason. Antoine Lavoisier was fifty years old and, among his many other legacies, left behind his Elementary Treatise on Chemistry, which was destined to change the world’s economic and social order.
In the splendour of the Industrial Revolution, the steam engine was the motor of economic progress. The physics of heat, which up until then had been merely a matter of intellectual curiosity, took centre stage. The entrepreneurs of the age were urged to improve the efficiency of steam machines. Building on Lavoisier’s studies, Nicolas Léonard Sadi Carnot, in his Borgesian Reflections on the Motive Power of Fire, then sketched out once and for all the ideal machine.
Seen today with privileged hindsight, there is something odd in this scientific epic that is reminiscent of the present situation with consciousness. Lavoisier and Carnot didn’t have the faintest idea what heat was. Even worse, they were stuck between myths and wrong-headed concepts. For example, they believed that heat was a fluid called caloric that flowed from a hotter body to a cooler one. Today we know that heat is actually a state–agitated and in movement–of matter. For those versed in the subject, the idea of the caloric seems childish, almost absurd.
What will future experts in consciousness think of our contemporary ideas? Today’s neuroscience is in a state of understanding equivalent to somewhere between Lavoisier and Carnot. The steam machine changed the eighteenth-century world in the same way computers and ‘thinking machines’ are changing ours now. Will these new machines be able to feel? Will they have their own wills, conceptions, desires and goals? Will they have consciousness? As was the case in the eighteenth century with heat, science must provide rapid responses to the understanding of consciousness, about whose fundamental substratum we still know almost nothing.
Pyschology in the prehistory of neuroscience
I like to think of Sigmund Freud as the Lavoisier of consciousness. Freud’s great speculation was that conscious thought is just the tip of the iceberg, that the human mind is built on a foundation of unconscious thought. We only access consciously the conclusions, the outcomes, the actions evoked by this massively parallel device of unconscious thought. Freud made this discovery blindly, by observing remote and indirect traces of consciousness. Today, unconscious cerebral processes can be seen, brought to light in real time and with high resolution.
The bulk of Freud’s work and almost all of his intellectual lineage were built on a psychological framework. However, over the course of his life, he also formed a neurophysiological theory of mental processes. This progression seems reasonable. To understand breathing, a pulmonologist analyses how the bronchioles work and why they become inflamed. In much the same way, the observation of the structure and functioning of the brain and its tangle of neurons is a natural path for those wanting to understand thought. Sigmund Freud, a brilliant professor of neuropathology in addition to his work as the founding father of psychoanalysis, declared his intentions in one of his first texts, Project for a Scientific Psychology, which was published posthumously: to build a psychology that was a natural science, explaining the psychic processes as quantitative states determined by distinguishable materials of the nervous system. He added that the particles which make up psychic matter are neurons. This last conjecture–which has rarely been recognized–reveals Freud’s magnificent intuition.
In the last years of the nineteenth century, the scientists Santiago Ramón y Cajal and Camillo Golgi were embroiled in a very heated argument. Cajal maintained that the brain was made up of interconnected neurons. Golgi, on the other hand, believed that the brain was like a reticulum, like a continuous net. This epic scientific battle was settled by the microscope. Golgi, the great experimenter, developed a staining technique–still known today as Golgi’s method–to see what was previously invisible. This stain added contrast to the grey edges on a grey background of brain tissue and made them visible in the microscope, shiny as gold. Cajal used the same tool. But he was wonderfully skilled at drawing, which made him highly observant and, where Golgi saw a continuum, Cajal saw the opposite: separate pieces (neurons) that scarcely touched. Altogether demolishing the image of science as a world of objective truths, the two bitter enemies together won the first Nobel Prize for Physiology. It is one of the loveliest examples of science celebrating, with its highest award and at the same ceremony, two opposing ideas.
Many years have passed since then, with many far more powerful microscopes, and we now know that Cajal was right. His work was the foundation of neuroscience, the science that studies neurons and the organ those neurons make up, along with the ideas, dreams, words, desires, decisions, yearnings and memories that they manufacture. But when Freud began his Project for a Scientific Psychology and sketched his brain model of a network of connected neurons, the debate between neurons and reticula was still unresolved.
Freud understood that the conditions were not yet ripe for a natural science of thought and, as such, he would not be the one to promote his Project. Yet today we–the heirs to Freud’s work–are no longer working blindly as he was then, and we can take up the baton. It may now be prime time for the Project of conceiving a psychology based on the biology of the brain.
Freud working in the dark
In his Project, Freud sketched out the first neuronal network in the history of science. This network captured the essence of the more sophisticated models that today emulate the cerebral architecture of consciousness. It was made up of three types of neurons, phi, psi and omega, that functioned like a hydraulic device.
The phi (Φ) are sensory neurons and form rigid circuits that produce stereotypical reactions, such as reflexes. Freud predicted a property of these neurons that today has been proven by much experimental evidence: they live in the present. The Φ neurons fire rapidly because they are composed of permeable walls that release pressure soon after acquiring it. Thus they encode the stimulus received and, almost instantly, forget it. Freud was wrong about the physics–the neurons fire electrically and not hydraulically–but the principle is almost equivalent; the sensory neurons of the primary visual cortex are biophysically characterized by having rapid charge and discharge times.
The Φ neurons also detect our inner world. For example, they react when the body registers that hydration is necessary, by producing a feeling of thirst. So these neurons transmit an objective, a sort of raison d’être–searching out water in this case–but they do not have memory or consciousness.
Freud then introduced another type of neuron, called the psi (Ψ), which is capable of forming memories, allowing the network to detach from the immediacy of the present. Ψ neurons are made up of an impermeable wall that accumulates and stores, in isolation, our history of sensations. Today we know that the neurons in the parietal and frontal cortices–that codify working memory (active, for example, when remembering a phone number or an address for several seconds)–function similarly to Freud’s conjecture. Except that, instead of ha
ving an impermeable casing, they manage to keep their activity alive through a feedback mechanism; like a loop that allows them to recoup the charge they are constantly losing. Yet long-term memories–for example, a childhood memory–work in a very different way from what Freud put forth. The mechanism is complex but, in large part, the memory establishes itself in the pattern of connection between neurons and in their structural changes, not in their dynamic electrical charge. This results in much more stable and less costly memory systems.
Freud was visionary in his anticipation of another conundrum. Since consciousness feeds on past experiences and representations of the future, it cannot be attached to the Φ system, which only codifies the present. And since the contents of consciousness–which is to say, what we are thinking–are constantly changing, they cannot correspond to the Ψ system, which doesn’t change over time. With manifest annoyance, Freud then described a new system of neurons that he called omega (Ω). These neurons can–like those of memory–accumulate charge over time and, therefore, organize themselves in episodes. His hypothesis was that the activation of these neurons was related to awareness and that they could integrate information over time and jump, like in hopscotch, between states to the rhythm of an internal clock.
We will see that this clock does indeed exist inside our brains, organizing conscious perception into a sequence of film stills. As we will see at the end of this chapter, the existence of such a clock can explain an intriguing and common illusion that Freud could not have seen: for example, why, when we are watching a motor race, do the wheels sometimes seem to turn in the wrong direction?
Free will gets up off the couch
One of the most powerful ideas in Freud’s neuronal circuit was barely hinted at in his Project. The Φ neurons (sensations) activate the Ψ neurons (memory), which in turn activate the Ω neurons (awareness). In other words, consciousness originates in the unconscious circuits, not in the conscious ones. This flow set a precedent for three interwoven ideas that proved decisive in the study of awareness:
(1) Almost all mental activity is unconscious.
(2) The unconscious is the true motor of our actions.
(3) The conscious mind inherits and, to a certain extent, takes charge of those sparks from the unconscious. Consciousness, thus, is not the genuine author of our (conscious) actions. But it, at least, has the ability to edit, modify and censure them.
This triad, a century later, has become tangible through experiments that hack into the brain, questioning and delineating the notion of free will. When we choose something, was there ever really any other option? Or was everything already determined and we only had the illusion of being in control?
Free will leaped into the scientific arena in the early 1980s with a foundational experiment by Benjamin Libet. The first trick was to reduce freedom of expression to its most rudimentary form: a person freely choosing when to push a button. That relegated it to a single act of just one bit. It is a simple, minimal freedom, but freedom nonetheless. After all, we are all free to push the button when we feel like it. Isn’t that so?
Libet understood that in order to reveal this fundamental enigma he had to register three channels simultaneously.
First of all, the exact moment in which a supposedly free decision-maker believes he or she is making a decision. Imagine, for example, that you are on a diving board, deliberating over whether or not to dive into a pool. The process can be long, but there is a fairly precise moment in which you decide whether to dive. With a high-precision watch, and switching the vertigo of the diving board for a mere button, Libet recorded the exact moment in which the participants felt they were making the decision to push the button. This measurement reflects a subjective belief, the story that we tell ourselves about our own free will.
Libet also recorded participants’ muscular activity in order to pinpoint the precise moment when they made use of their supposed freedom and pushed the button. And he discovered that there was a small lag of one third of a second between when they believed they had made a decision and when they carried it out. This is reasonable and simply reflects the conduction speed of the motor signal needed to execute the action. To measure brain activity, he used an electroencephalogram (EEG); a few small electrodes placed at the surface of the scalp. And the extraordinary finding in Libet’s experiment showed up in this third channel. He discovered a trail of cerebral activity that allowed him to identify the moment in which participants would press the button, half a second before they themselves recognized their intention. It was the first clear demonstration in the history of science of an observer able to codify cerebral activity in order to predict another person’s intention. In other words, to read their thoughts.
Libet’s experiment gave rise to a field of investigation that produced countless new questions, details and objections. Here we will only look at three of them. The first two are easily solved. The third opens up a door to something about which we have very little knowledge.
A general criticism of this experiment (made by Libet himself and many other scientists who followed this work) is that the moment in which the decision is made is not always clear. And even if it were, his method allowed for a degree of imprecision in the recording. A second natural objection is that before making a decision there is a process of preparation. One can get into diving position before having decided to dive into the pool. Many of us, in fact, glumly retreat from the board without taking the plunge. Perhaps what Libet observed was the brain’s preparatory circling around the decision.
These two objections are resolved in a contemporary version of Libet’s experiment, conducted by John-Dylan Haynes in 2008, with two subtle but decisive differences. First of all, the resolution of the measuring instrument is improved by using magnetic resonance instead of the electroencephalogram with fewer channels than Libet employed, allowing for greater precision in decoding cerebral states.
Secondly, participants’ freedom of expression is doubled: they can now choose between two buttons. This minimal variation allowed Haynes to distinguish the choice (right or left button) from the action (the moment of pushing one of the buttons).
With this addition of the second button and the new technology, the magnifying glass used for searching out an unconscious seed in our apparently free and conscious decision-making became much more effective. Based on the pattern of activity in a region of the frontal cortex, it was possible to decipher the content of a decision ten seconds before a person felt that they were making it. The region of the brain that denotes our future actions is vast but specifically includes a zone in the more frontal and medial part that we are already familiar with: the Brodmann Area 10, which coordinates inner states cohesively with the outer world. In other words, when a person actually makes a decision, they do not know that in fact it had already been made a few seconds earlier.
The more difficult problem with Libet’s experiment is knowing what happens if someone intentionally decides to push the button but then deliberately halts before doing so. Libet himself responded to this, arguing that consciousness has no vote but does have a veto. Which is to say, it doesn’t have the capability or the freedom to set an action into motion–the task of the unconscious–but it can, once this action becomes observable to it, manipulate it and eventually stop it. Consciousness, in this scenario, is like a sort of preview of our actions in order to filter and mould them.
In Libet’s experiment, if someone decides to press the button and then changes their mind, a series of cerebral processes can be observed; the first codifies the intent to act that is never realized; later, a very different second process reveals a system of monitoring and censorship governed by another structure in the frontal part of the brain that we have already looked at, the anterior cingulate.
Does the conscious decision to halt an action also stem from another unconscious seed? This is still–as I understand it–a mystery. The problem is sketched in Borges’s fable about chess pieces:
God m
oves the player, who moves the piece.
What God behind God gives rise to the plot
of dust and time and dreams and agony?
In this endless recursion of wills that control wills (the decision to dive into the pool, then the hesitation and the decision to stop, then another that soothes the fear so the first decision can continue its course …) a loop emerges. It is the brain’s ability to observe itself. And this loop is perhaps, as we will see further on, the basis of the principle of consciousness.
The interpreter of consciousness
The brain’s two hemispheres are connected by a massive structure of neuronal fibres called the corpus callosum. It is like a system of bridges that coordinates traffic between the two halves of a city divided by a river; without the bridges, the city is split in two. Without the corpus callosum, the cerebral hemispheres are isolated from each other. Some years back, in order to remedy some forms of epilepsy that were resistant to pharmaceutical treatment, some patients underwent a corpus callosotomy, a surgical procedure in which the two hemispheres were split apart. Epilepsy is, to a certain extent, a problem of brain connectivity that results in cycles of neuronal activity that feed on themselves. This surgical procedure interrupts the flow of currents in the brain and is a dramatic but effective way of putting paid to these cycles and, with them, epilepsy.
The Secret Life of the Mind Page 11
