At the British Neuroscience Association (BNA)’s Festival of Neuroscience in April 2019, we were lucky enough to sit down with some influential neuroscientists to discuss their work. We’ve assembled these transcripts into our BNA Interview Series. Here we interview the University of Sussex's Anil Seth, whose research explores the mysteries of consciousness.
Ruairi Mackenzie (RM): In the past you’ve mentioned that if we were somehow able to simulate the human brain and create a digital version of it, that wouldn’t necessarily be a replication of consciousness and that consciousness is something that comes from our biology instead. If efforts like the Human Brain Project were able to create a simulation of the brain, would we be able to use that simulation to replicate disorders of cognition, or is consciousness essential to being able to study the brain?
Anil Seth (AS): I think you can certainly make use of detailed brain simulations without making any commitment to whether these simulations are conscious or would be conscious at some unknown level of detail and fidelity. In the same way that computational models can always be useful. We make very good use of large-scale computation models of weather systems to make predictions about the weather and about possible interventions in the weather, but we treat them as simulations. You don’t worry about whether these simulations instantiate weather in any sense. I think detailed computational models of perceptual systems, of decision-making systems, can be very informative for understanding disorders in psychiatry and neurology, that affect conscious experience. But we don’t have to worry about whether the simulations themselves actually generate consciousness for them to be useful that way.
RM: A question from our audience. What’s happening in our consciousness when you experience déjà vu?
AS: I put déjà vu in the same category as things like out of body experiences. They’re very, very powerfully vivid for the people that have them. I’ve not had an out of body experience, but I think most people have… I’ve definitely had an experience in déjà vu and the compelling nature of them, like “This has happened before,” is so overwhelming. I think in neuroscience, there’s sometimes a tendency to discount these experiences. To say, well that can’t happen, so it didn’t happen. But no, people have these experiences, but it doesn’t mean that the experiences signify what they are often taken to. Just as when you have an out of body experience, it doesn’t mean that your soul has left, flown out of the top of your skull and is taking a joy ride around the room. If you have a vivid experience of déjà vu, it doesn’t mean that you’re literally reliving some past event.
What it means is that we have mechanisms of autobiographical and episodic memory that are capable of allowing us to engage in a kind of mental time travel. There are also parts of our brains that generate a feeling of familiarity and I think what’s happening in déjà vu is that these systems are activated together in a more joint way than would normally happen. The problem, of course, is that it’s really, really difficult to experimentally study these kinds of phenomenon because they just happen, and you can’t experience déjà vu on demand and study it. It would be great if we could. I think we might get close with things like virtual reality because it’s actually possible to artificially engineer situations that do repeat. Certainly, in my line of work, this is one reason I find studying consciousness distinctive and fascinating because we can start to take experiences like that and think of ways that we could stimulate or operationalize them. Or somehow bring them into the lab using the technologies that we have available now.
RM: In your research and the way you talk about consciousness, I’m reminded of neuroscience but also, of philosophy and questions about the nature of reality. Do you think neuroscientists and philosophers have a lot to learn from each other? Do you think they are currently learning from each other? Could they do better in sharing ideas from between the two disciplines?
AS: I think the answer is yes to all three. I’ve certainly learnt a lot and still have a lot to learn from philosophers and I’m very lucky and take very seriously the opportunities I have to talk with philosophers. For me, the really exciting programs in consciousness research inevitably involve strong collaborations with philosophers. The Association for the Scientific Study of Consciousness was built on the premise that we integrate philosophy, neuroscience and psychology with equal prominence to all of those approaches and mix them up as much as possible. I’m also involved in this program organized by the Canadian Institute for Advanced Research, which again, has philosophy built in from the ground up. I think it’s essential in a number of ways.
The first reason it’s essential is, of course, that philosophers have been thinking about consciousness forever and can teach us how to think about it and when you’re trying to explain an apparently mysterious phenomenon, you have to do a lot of conceptual groundwork first. What is consciousness? I’m not saying we have a precise scientific definition, but we need to make distinctions about different forms of consciousness and make them clearly, so we know what we’re talking about. We also need to know how to interpret the results of experiments, and philosophy can help there too. In general, philosophy can motivate in experiments, it can guide their interpretation. But what philosophy can’t do is, of course, answer many of the questions that it poses. Philosophers, in general, are extremely good at asking questions. They’re not so good at giving the answers but that’s fine – it’s all part of the process. I think it’s extremely important.
RM: Another audience question - could consciousness be an illusion?
AS: One of my great mentors and inspirations is the philosopher, Daniel Dennett, who as many of you might know, is famous for his book, Consciousness Explained, which I read when I was an undergrad, 25 years ago. He’s often taken to say consciousness is an illusion. I don’t think he actually means that, and I certainly don’t think that. In some sense, consciousness is the only thing that can’t be an illusion. Everything else could be an illusion. We don’t know what the world is really made of. This table in front of you and I, something is there but it’s not actually white. That’s just light rays. White is something that our brain decides to label certain patterns of invariant electromagnetic radiation but if I hit you with a stick…
RM: Please don’t.
AS: I’m not going to do it! If you have a toothache, that’s pain. That’s not an illusion. Everything that we know, we know through consciousness, conscious experiences. It’s perhaps the only thing that we can be absolutely sure exists.
RM: So pain is a combination of maybe, individual illusions, then, that come together to make our consciousness.
AS: Yeah, it could be. We could be mistaken about what our conscious experience signifies, and there might be illusions about what we think it would take to explain consciousness. It’s a very common belief, something that seems compelling to most people (and me) that consciousness is a different kind of thing to the rest of the world. That many of us have this intuitive dualism that harks back to Descartes, that there’s the stuff of consciousness and there’s the material world. How they relate is what David Chalmers has called the hard problem with consciousness. Now, it could be that the existence of a hard problem is an illusion, that once you’ve explained how neural systems work, and why an experience of color is different from an experience of smell – once we’ve explained everything that we can, that there’s nothing left over. That might be the case. Of course, we don’t know, so we’ve got to get to that stage, but I certainly don’t think that consciousness is an illusion.
RM: Another great question from our audience – actually moving beyond the brain – could consciousness be in any other part of the body than the brain?
AS: I suppose it’s possible. I personally don’t think so. There’s two ways to take this. First is to say that certainly, the body is important for consciousness. Many of the things that we experience, especially things like emotion and mood, fundamentally depend on the body and the way I think about consciousness and the brain in general is as a way of keeping the body alive. Most of our conscious experiences can be better understood as reflecting how well the brain is doing at keeping the body alive. The body is fundamental.
But right here and right now, what is the substrate of your conscious experience? Here, it doesn’t even seem that we need the whole brain. One of the fascinating facts about consciousness is that it seems like you can get rid of your cerebellum, a brain region that’s important for movement, coordination, and organization of your thinking, that has about three quarters of the number of neurons in the whole of your brain and you will not lose consciousness.
AS: You’ll be disordered and hazy, but from the few cases that we know of it seems that you just don’t need your cerebellum to be conscious. Why is this? If you look at the organization of the cerebellum, it’s many, many neurons but they’re organized into relatively independent, small circuits that repeat. Like a crystal structure, whereas the cortex and other parts of the brain have a more complicated recurrent architecture. It’s still surprising to me that you can get rid of three quarters of your brain, and it doesn’t matter. If you can get rid of over half your brain and still be conscious, then I think you can also get rid of other parts of your body and still be conscious.
RM: Some changes to the brain make people more resistant to anesthetic or cause permanent insomnia. Are there any other parts of the brain which we think are involved in the maintenance of consciousness?
AS: The hard thing here is to distinguish those parts of the brain or processes which might be thought of as enabling functions. In the same way, you need electricity or an on switch before your computer works but it doesn’t really explain very much about how a computer works or a TV works just by saying you need to turn it on and give it electricity. There are certainly parts of the brain in the brain stem and in the thalamus, deep in the thalamus that need to be intact to be conscious but it’s unclear how much about consciousness is explained by that fact.
RM: About seven years ago, you wrote a column for The Guardian in which you raised nine questions about neuroscience. I was reading that earlier today, so I guess I have some questions from you to yourself. Here’s one: in the last few years, how has our understanding of consciousness in animals improved?
AS: I don’t think any major advances. It’s a really hard question because the methodological problems are intense. One of the most common problems is that the only way to really know about consciousness is through subjective report. I have to ask you what your experience is and it’s very difficult to do that in non-human animals, and in human babies. There are other cases too. It’s a very difficult area to make big jumps in but I think the incremental progress has been very interesting. I mean, I’ve been particularly interested in the octopus for a very long time.
RM: The octopus?
AS: Because they’re very removed in the evolutionary tree from humans. Our common ancestor was something like a barnacle or a sponge or something very simple, but they still have brains made of neurons. They have quite a lot of neurons. They’re very smart and if you ever get a chance to spend time with an octopus, they really give you the sense of an intelligent presence being there. That’s a dangerous sense to rely on as we tend to anthropomorphize a bit too much but nonetheless, they are very intelligent. They can learn through simply observing other octopuses do things and yet, they seem like aliens to us.
My intuition is there’s got to be something it is like to be an octopus but it’s very difficult to demonstrate that. Apart from just slowly accumulating evidence. We now know a bit more about octopus cognition and octopus neurophysiology. It was recently found that if you give octopuses MDMA, they become more pro-social. They’re normally not that social. It was really intriguing shared similarity, even after such a large amount of evolutionary divergence. But we certainly don’t have this litmus test or gold standard test for consciousness in other animals.
RM: What about understanding of consciousness in what we term, minimally conscious people – have there been any recent advances?
AS: Yes. Now, here is one of the areas where there’s been most dramatic progress. It’s really an area where the progress can be traced directly to consciousness being the focus of research rather than just neurology or medicine in general. These are the cases of people who’ve suffered major brain injury and have been diagnosed in what’s now called the unaware wakeful state. These are people who are still alive, and they still go through sleep and wake cycles, but they appear to be unconscious from the outside. They will not respond to commands. They make no voluntary actions; they don’t engage with their environment at all and so are typically diagnosed as not having any awareness. They can live for a very long time, so this is a big challenge in neurology and medicine.
Back in 2006, nearly 13 years ago, Adrian Owen and Mélanie Boly and colleagues made a breakthrough in this area by showing that certain unaware wakeful patients were conscious, and they did this through a very clever experiment. To explain it simply they asked these patients to imagine one of two things. Imagine playing tennis or imagine walking around their house. Of course, behaviorally, they don’t seem to be responding at all but this subset of patients, you could tell, from their brain imaging patterns, that they were engaging those parts of the brain that light up if you or I were to imagine the same things. These aren’t just areas that respond to language or to sound. For example, if we asked you to play tennis, areas of your brain that represent smooth movement are at play.
RM: Tennis is not smooth for me.
AS: Not that smooth for me either but distinct compared to walking around your house, where you see areas involved in navigation light up. That was the first step and that research has led to a lot of interesting follow ups about the efficiency with which this can be done using more portable bedside equipment like EEG rather than MRI. You can use these techniques for communication. You can ask people, are you in pain? If yes, imagine walking around your house. If no, something else. That’s really changed the field and we’ve also seen an increasingly refined set of diagnoses. I think we’re getting a much better grip on being able to measure residual consciousness and to be able to develop prognoses about how people may or may not recover. What’s lacking of course, are powerful methods of intervention and that’s the next step. Can we use things like deep brain stimulation or other sorts of pharmacological intervention to take a particular subset of these patients and see some recovery? That would be very exciting.
Anil Seth was speaking to Ruairi J Mackenzie, Science Writer for Technology Networks. Interviews have been edited for length and clarity.