Famed Neuroscientist Christof Koch Speaks on Consciousness


Despite all of my articles, I really have very few things that interest me. Actually, just two things: What is the nature of reality. And, what is the nature of consciousness.

I am privileged to have an inside track on both of these pursuits at UC Santa Barbara. I enjoy attending the Physics Department talks on cutting edge research as well as the SAGE Center for the Study of the Mind talks. For many years we were fortunate to have the leadership of neuroscientist Michael Gazzaniga at the SAGE Center. He helped pioneer split brain research as a tool for understanding consciousness in humans.

UCSB Psychology Professor Jonathan Schooler has stepped up to that leadership role of SAGE recently. And he is the wizard of connections to amazing people. In recent years Jonathan has included me in his research lab, for which I am very grateful. Jonathan’s latest amazing connection was with Christof Koch, bringing him here to speak.

Christof Koch is a leading neuroscientist in the field of consciousness. I have seen him speak quite a few times over the years at the Association for the Scientific Study of Consciousness (ASSC) conferences and at The Science of Consciousness conferences. Koch is the president and chief scientist of the Allen Institute for Brain Science. Founded by Microsoft co-founder Paul Allen. “Dedicated to accelerating the understanding of how the human brain works”.


Koch started his recent SAGE talk noting that consciousness is the only way that he knows anything exists. It would be absurd that this central aspect of life would be off limits to study! As a result, he titled his talk “The Elephant in the Room – Integrated Information Theory and Consciousness”.

He began by describing two conscious experiences. The first, quite extraordinary. A Near Death Experience (NDE). The second, more ordinary. Running through a forest, taking in the visual beauty and the sounds around him.

Koch noted that you can know someone your whole life, but you can never directly have their experiences. Studying consciousness is harder than studying black holes, electrons or viruses. Those are all third person.

Descartes wrote that consciousness is the only thing he is utterly certain of. Any ontology must start from this unassailable observation. We think the world is made of atoms. But we have no direct knowledge of atoms. We only have direct knowledge of our conscious experiences.


Philosopher David Chalmers famously coined the term “The Hard Problem of Consciousness”. Chalmers imagined a world just like ours, but where everyone is a zombie with no actual conscious experiences.

Not only do we have to explain that we have feelings. We have to explain why they are as they are. Space is extended, time flows, colors are a certain way, smells are a certain different way. Being in love is a special feeling. This has to be explained with science.

People used to think the heart was the center of consciousness. It was the only part that was visibly moving. Koch noted that the brain of a mouse is indistinguishable from a human brain at the level of the neurons.


Francis Crick won the Nobel Prize for his contribution to discovering the structure of DNA. He went on to work on understanding consciousness. Including collaborating with Koch. Here they were together.

Together they worked on the “neural correlates of consciousness” (NCC). Defined as the minimal neural mechanisms that are together necessary and sufficient for experiencing any conscious percept.

In the diagram above, Koch was showing the relationship between a German Shepherd dog in the external world and its representation in the brain. Koch and Crick wondered if the NCC would be the same when seeing the dog as when imagining one.

They were seeking what biological systems were key to consciousness. If the heart stops, you lose consciousness in nine seconds. It is an enabling factor for consciousness, but it doesn’t give rise to consciousness.

The Ascending Reticular Formation of the brain seems important. Research is based on evidence gathered from lesions (damage) to brain regions. From loss of function. From stimulating the brain. From gain of function. And from direct recording of brain signals and from neuroimaging.

Broca’s Area of the brain was identified in the 1850s as a result of observations of someone who lost the ability to speak.

The front areas of the brain are key to some of the most interesting behaviors of human beings. Creative thought and planning. But loss of the frontal areas has no effect on consciousness.

Before performing brain surgery, a surgeon will stimulate brain areas to be sure there is no problem cutting that area. The patient is awake and fully aware of what is happening, so that he or she can report on the effects. This has helped build up a map of brain function.


Koch wants to distinguish the NCC from the events that precede or follow a conscious experience. Including selective attention, performing tasks and other behaviors.

The cerebellum is a huge part of the brain containing most of the neurons in the entire brain. 69 billion neurons out of 86 billion in the entire brain. It is important for smooth movement. If it is damaged, a person may have slurred speech or an unsteady gait when walking. But damage or loss of the cerebellum causes no disruption of consciousness.

Koch showed an image of a Chinese woman’s brain that entirely lacked a cerebellum.

He explained in computer science terms that the cerebellum’s wiring is entirely “feed forward”. He thinks this is key to understanding consciousness.

Koch noted that direct electrical stimulation of the brain can alter the sense of self:

The mouse brain has 5,000 cell types. Not all cortex cells are the same. We have a lot to learn.


We need a consciousness detector for practical reasons. In the case of Traumatic Brain Injury (TBI) a person might open their eyes but not respond. After 3-5 days, the medical team will talk to the family about withdrawing life support. 80% of these patients will die of withdrawal of support. But 20% of them are covertly conscious.

In recent years a technique has been developed to accurately predict this covert consciousness. A jolt is given to the brain and the resulting EEG is observed. The key is to note the complexity of the resulting signal. How do we measure the complexity? In modern times we use “compression algorithms” to compress images in the form of JPG or TIFF, for example. It turns out that these compression algorithms give a good measure of complexity.

If the EEG signal undergoes very little compression, it means that it is complex.

But Koch also noted that there are limitations to what NCC can tell us. This is all still an empirical, third person study. It does not directly get to the first person experience.


In 1998, Christof Koch bet David Chalmers that the mechanism by which the brain’s neurons produce consciousness would be discovered by 2023. Here Koch paid the bet last year at the ASSC Conference in New York.


We don’t just want correlates. We want a testable theory. He suggests looking at engineered systems, large language models and cerebral organoids.

In stark contrast to his view is Functionalism. This view holds that every mental state is nothing but its functional role and its causal relation. Philosopher Daniel Dennett is one of the most famous advocates of this position.

Dennett has also been a SAGE visiting professor at UCSB and I was privileged to have time with him. He seems to deny consciousness in any meaningful sense. He denies what philosophers call “qualia”. The experience of the yellowness of yellow. The pain of a toothache. The pain of a toothache is nothing more or less than how you behave in a different way for having one. According to Dennett. “He is confused about pain!” Koch exclaimed.

Functionalism was dominant in the Anglo-Saxon world and in Big Tech, Koch noted. He went on to list specific functional theories of consciousness.

Global Neuronal Workspace Theory. Recurrent Processing. Higher Order Thought. Attentional Schema. All based on computational functionalism.

He had observed that consciousness correlates with 40Hz signals in the brain. But… “Why does that turn water of the brain into the wine of consciousness?”


Which brought Koch to the theory he is favoring these days: Integrated Information Theory (IIT). Developed by neuroscientist Giulio Tononi at the University of Wisconsin, Madison. I had the privilege of attending two different workshops with Tononi at different conferences. I have some idea of what he is doing, but I have to say I still don’t understand some basic concepts of the theory.

IIT starts with some basic postulates or axioms, as one does in learning geometry. Here is a list from the Internet Encyclopedia of Philosophy:

  1. Following from the fundamental Cartesian insight, is the axiom of existence. Consciousness is real and undeniable; moreover, a subject’s consciousness has this reality intrinsically; it exists from its own perspective.
  2. Consciousness has composition. In other words, each experience has structure. Color and shape, for example, structure visual experience. Such structure allows for various distinctions.
  3. The axiom of information: the way an experience is distinguishes it from other possible experiences. An experience specifies; it is specific to certain things, distinct from others.
  4. Consciousness has the characteristic of integration. The elements of an experience are interdependent. For example, the particular colors and shapes that structure a visual conscious state are experienced together. As we read these words, we experience the font-shape and letter-color inseparably. We do not have isolated experiences of each and then add them together. This integration means that consciousness is irreducible to separate elements. Consciousness is unified.
  5. Consciousness has the property of exclusion. Every experience has borders. Precisely because consciousness specifies certain things, it excludes others. Consciousness also flows at a particular speed.


Koch contrasted IIT with the 19th century idea of the “luminiferous ether”. The ether was supposed to be the medium of light in the same way air is the medium of sound. But it had no causal power. It could not be observed. It solved no problems.

In contrast, Koch argued that IIT does have causal power. Regardless of the hardware “substrate” of the system.

The central measure in IIT is called “phi” and is a measure of the complexity or irreducibility of the system. A circuit or system has more or less phi depending on how it is wired together. Remember Koch talking about the “feed forward” structure of the cerebellum? That is what he was talking about. Such a feed forward structure has zero phi, even if it is enormously complex and allows us to perform enormously complex behaviors.

Phi is a single number. But the connections of a circuit create a shape in a hyperspace of higher dimensions. It is that shape that gives the specific experience of specific “qualia”.


Phi is not just about actual active connections. It is also about possible connections. This is a central aspect of IIT that is different from most understandings of the brain based on computer models. A brain circuit can contribute to phi, even if it is not active. Because it can become active. He contrasts a “silent” area with a “silenced” area.

He made an analogy to the famous “dog that did not bark” observed by Sherlock Holmes in Silver Blaze, a story by Sir Arthur Conan Doyle. A race horse was removed from a stable. But the dog did not bark. The dog was not silenced. It was silent. Silent means it could have been active, but it was not. Meaning that the dog knew the person who removed the race horse.

In the IIT view, consciousness is not about intelligence. Koch showed a diagram mapping organisms and synthetic systems on a plot of consciousness vs intelligence. Powerful programs like Alpha Go and Chat GPT are intelligent, but have zero phi and zero consciousness. But a brain organoid in a Petri dish can have high phi but no intelligence at all.

Koch summarized his view by noting that to study consciousness, we have to start with consciousness and go out into the world from there. Not the other way around.


One person asked if a simulation of a brain could be conscious. He says it cannot, according to IIT. He made the analogy: A simulation of a storm does not cause the computer to get wet inside. He did leave the door open that perhaps a quantum computer or a neural network type computer running the simulation could be different. It is all about the phi of the actual computer, not of the simulation.

Someone asked if consciousness is about the ability of a system to model itself. Koch said no. A thermostat can model the temperature, but it is not conscious, even a little. The same goes for elaborate systems with internal models of themselves.


I will note that some of us had a separate meeting at the home of Jonathan Schooler. We were able to get into another range of issues. I asked Koch about his view that IIT could also give reality to free will.

Koch returned to the “causal power” aspect of IIT. Consciousness is that structure in hyperspace. That structure has real causal power. Nothing supernatural or quantum mechanical is involved. It is all about how the circuits are wired up.

Our meeting was also a chance to ask about his research with psychedelics and his own personal experiences with them. Having seen him speak over a period of decades, it is clear that his personal experiences with psychedelics have opened him up to possible views of consciousness that he would not have considered in the past.

He said that there are at least three reasons for his interest in psychedelics:

  1. They clearly have therapeutic value. Starting with Nixon’s War on Drugs, this research was shut down. But it is slowly coming back. Koch is one of the few researchers with a license to do this research.
  2. Psychedelics can rapidly change the nature of conscious experience. This can be observed in an MRI scanner.
  3. He wonders whether they can teach us about “what truly exists”. He participated in a ceremony where he was able to meet God. But he still has to take out the trash.

He is still struggling to integrate his direct experiences with a theory of consciousness and of reality. His final words when he met with us: “Ultimately, I am an empiricist”.

Here Koch kindly posed with me and with Jonathan.


To learn more about Koch’s current ideas on consciousness and on psychedelics, please read his newest book “Then I Am Myself the World: What Consciousness Is and How to Expand It”.

– Robert Bernstein


Written by sbrobert

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  1. I am in awe of the response to my article. Over 30,000 views. And I am getting messages from people from far away. Koch is a super star, so I am sure it is about him, not me.

    @yin yang Thank you for your interest. Hyperspace of higher dimensions is a very ordinary term in mathematics. Nothing woo about it. In my day jobs of physics, math and engineering we used higher dimensions of space in many applications. In this case it is modeling a web of neural connections.

    It may be speculative, but Integrated Information Theory is not “woo”. Here was a layman level article in Psychology Today about it:

    Thanks again for the interest.

    • Wonderful Article!!!! Thank you so much for sharing!! I hope it’s okay that I shared it. I am so incredibly blown away by topics like this, especially this one- I have had insomnia since I was a child, and I have had multiple concussions, and my mom and I have always been able to manipulate our dreams, and we have secret places where we go in our dreams and things…but lately I’ve been pretty much been what I can only describe as lucid dreaming I guess..anyway thanks again!! 💞💞💞

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