Being You: A New Science of Consciousness

by Anil Seth

Conscious content is about what we are conscious of—the sights, sounds, smells, emotions, moods, thoughts, and beliefs that make up our inner universe. Conscious contents are all varieties of perception—brain-based interpretations of sensory signals that collectively make up our conscious experiences.

The experience of “being a self” is a subset of conscious contents, encompassing experiences of having a particular body, a first-person perspective, a set of unique memories, as well as experiences of moods, emotions, and “free will.” Selfhood is probably the aspect of consciousness that we cling to most tightly, so tightly that it can be tempting to confuse self-consciousness (the experience of being a self) with consciousness itself (the presence of any kind of subjective experience, of any phenomenology, whatsoever).

There are as many different ways of being conscious as there are different conscious organisms.

What makes the difference between being conscious at all and being a chunk of living meat, or lifeless silicon, without any inner universe?

In thermodynamics, temperature is a large-scale property of the movement of the molecules within a substance; specifically, the mean molecular kinetic energy. Faster movement, higher temperature.

measurement turns the qualitative into the quantitative, the vague into the precise.

While the two are often highly correlated, consciousness (awareness) and wakefulness (arousal) can come apart in various ways, which is enough to show that they cannot depend on the same underlying biology.

Consciousness instead seems to depend on how different parts of the brain speak to each other. And not the brain as a whole: the activity patterns that matter seem to be those within the thalamocortical system—the combination of the cerebral cortex and the thalamus

To test how different parts of the cortex were talking to each other, they stimulated activity in one location and recorded how this pulse of activity spread to other cortical regions over space and time. They did this by combining two techniques: EEG and transcranial magnetic stimulation (TMS).

different parts of the brain—in particular the thalamocortical system—are communicating with each other in much more sophisticated ways during conscious states than during unconscious states.

The approach is called “zap and zip”: use TMS to zap the cortex, and use a computer algorithm to “zip” the response, the electrical echo, into a single number.

We also found that complexity during rapid eye movement (REM) sleep is much the same as during normal conscious wakefulness, which makes sense because REM sleep is when dreaming is most likely—and dreams are conscious.

The ability to measure conscious level independently from wakefulness is not just scientifically important, it is potentially game-changing for neurologists, and for their patients.

In a 2010 study led by Martin Monti, a patient who had been admitted with a diagnosis of vegetative state was able to answer yes/no questions by imagining playing tennis for “yes” and imagining walking around their house for “no.”

recent analysis suggesting that between 10 and 20 percent of vegetative state patients might retain some form of covert consciousness, a number which would translate into many thousands across the world.

Consciousness has many properties, and it is a mistake to confuse the expression of the particular set of properties typical of healthy adult humans with the essential nature of consciousness in all its forms, and then to assume that it sits at the top of a unidimensional scale.

In the psychedelic state, vivid perceptual hallucinations are frequently accompanied by unusual experiences of selfhood often described as “ego dissolution,” where the boundaries between self and world, and other people, appear to shift or dissolve.

the psychedelic state might represent not only a change in conscious contents, but also a change in overall conscious level.

Following Hofmann’s self-experimentation, there had been a brief flowering of studies exploring the potential of LSD for treating a range of psychological disorders, including addiction and alcoholism, with very promising results. But the subsequent uptake of LSD as a recreational drug and as a symbol of rebellion, evangelized by Timothy Leary among others, led to pretty much all of this research being shut down by the end of the 1960s.

Psychedelic drugs influence the serotonin system by binding strongly to a specific serotonin receptor, the 5-HT2A receptor, which is found throughout much of the brain.

Networks of brain regions that are usually coordinated in their activity—so-called “resting-state networks”—become uncoupled, and other regions that are usually more or less independent become linked.

The results were clear and surprising: psilocybin, LSD, and ketamine all led to increases when compared to a placebo control. This was the first time anyone had seen an increase in a measure of conscious level relative to a baseline of waking rest.

The fact that a measure of conscious level is also sensitive to changes in conscious content makes clear that they are not independent aspects of consciousness.

Tononi and Edelman asked what was characteristic about conscious experiences in general. They made a simple but profound observation: that conscious experiences—all conscious experiences—are both informative and integrated.

Conscious experiences are informative because every conscious experience is different from every other conscious experience that you have ever had, ever will have, or ever could have.

At any one time, we have precisely one conscious experience out of vastly many possible conscious experiences. Every conscious experience therefore delivers a massive reduction of uncertainty, since this experience is being had, and not that experience, or that experience, and so on. And reduction of uncertainty is—mathematically—what is meant by “information.”

Exactly what is meant by consciousness being “integrated” is still much debated, but essentially it means that every conscious experience appears as a unified scene.

the hugely ambitious “integrated information theory” of consciousness—or IIT. This is Tononi’s brainchild, and more so than any other neuroscientifically motivated theory, it tackles the hard problem of consciousness head-on. IIT says that subjective experience is a property of patterns of cause and effect, that information is as real as mass or energy, and that even atoms may be a little bit conscious.

its approach is deeply mathematical and unapologetically complex. Of course, this is not necessarily a bad thing: nobody said that solving consciousness should be simple. Another objection is that the claims it makes are so counterintuitive that the theory must be wrong. This, too, is a dangerous intuition

For me, the bigger problem is that IIT’s extraordinary claims require extraordinary evidence, yet it is precisely the ambition of IIT—to solve the hard problem—that renders its most distinctive claims untestable in practice.

In IIT, Φ measures the amount of information a system generates “as a whole,” over and above the amount of information generated by its parts independently. This underpins the main claim of the theory, which is that a system is conscious to the extent that its whole generates more information than its parts.

According to IIT, the level of Φ is intrinsic to a system (meaning that it does not depend on an external observer), and it is identical to the amount of consciousness associated with that system. High Φ, lots of consciousness. Zero Φ, no consciousness. This is why IIT is the ultimate expression of a temperature-based view of consciousness.

There are many ways a system can fail to have high Φ. One is to score low on information. A minimal example is a single photodiode—a simple light sensor which can be either “on” or “off.” This has low or zero Φ because its state at any time carries very little information about anything.

The cerebral cortex, by contrast, is packed with densely interconnected wiring that is likely to be associated with high Φ. So then why does consciousness fade during dreamless sleep, anesthesia, and coma, given that this wiring doesn’t change? IIT says that, in these states, the ability of cortical neurons to interact with others is compromised in ways such that Φ vanishes.

Axioms, in logic, are statements that are self-evidently true, in the sense that they are generally agreed to require no additional justification.

Like any theory, IIT will stand or fall on whether its predictions are testable. The primary claim of the theory is that the level of consciousness for a system is given by its Φ. Testing this requires measuring Φ for real systems, and this is where the trouble starts.

The standard use of information in mathematics, developed by Claude Shannon in the 1940s, is observer-relative. Observer-relative (or extrinsic) information is the degree to which uncertainty is reduced, from the perspective of an observer, by observing a system in a particular state.

In order to measure intrinsic information, it is not enough merely to observe how the system behaves over time. You—as the scientist, the external observer—have to know all the different ways a system could behave, even if it never actually behaves in all these ways.

For my money, the best way forward is to retain the fundamental insight of IIT that conscious experiences are both informative and integrated, but to relinquish the conceit that Φ is to consciousness as mean molecular kinetic energy is to temperature.

Whenever we are conscious, we are conscious of something, or of many things. These are the contents of consciousness.

When trying to form perceptions, all the brain has to go on is a constant barrage of electrical signals which are only indirectly related to things out there in the world, whatever they may be.

the brain is a “prediction machine,” and that what we see, hear, and feel is nothing more than the brain’s “best guess” of the causes of its sensory inputs.

Here’s how the bottom-up picture is supposed to work. Stimuli from the world—light waves, sound waves, molecules conveying tastes and smells, and so on—impinge on sensory organs and cause electrical impulses to flow “upward” or “inward” into the brain.

what’s really going on is—I believe—quite different. Perceptions do not come from the bottom up or the outside in, they come primarily from the top down, or the inside out. What we experience is built from the brain’s predictions, or “best guesses,” about the causes of sensory signals.

The contents of perception, he argued, are not given by sensory signals themselves but have to be inferred by combining these signals with the brain’s expectations or beliefs about their causes.

Perceptual content, for Gregory, is determined by the brain’s best-supported hypotheses.

My own take on Helmholtz’s enduring idea, and on its contemporary incarnations, is best captured by the notion of perception as controlled hallucination

The third and most important ingredient in the controlled hallucination view is the claim that perceptual experience—in this case the subjective experience of “seeing a coffee cup”—is determined by the content of the (top-down) predictions, and not by the (bottom-up) sensory signals. We never experience sensory signals themselves, we only ever experience interpretations of them.

it is natural to think of perception as a process of bottom-up feature detection—a “reading” of the world around us. But what we actually perceive is a top-down, inside-out neuronal fantasy that is reined in by reality, not a transparent window onto whatever that reality may be.

If perception is controlled hallucination, then—equally—hallucination can be thought of as uncontrolled perception.