S1 Episode 50: Consciousness and Mental Time Travel

Our thoughts about the future are directly influenced by past memories and our deepest emotions. Dr. Joseph LeDoux, Professor of Neural Science at NYU, gives us an intriguing look at the areas of the brain that create the uniquely human experience of consciousness and how our ability to mentally “time travel” allows us to form a personal awareness of our place In the world. 

Dr. Philip Stieg: Today, we’re going to explore what emotions are and why human consciousness is both an evolutionary asset, but also a potential threat to our long-term survival as a species. I’m very happy to welcome to our show a leading neuroscientist author, an indie rock musician, Dr. Joel LeDoux. Joe is a professor of neuroscience at NYU. His work is focused on the brain mechanisms of memory and emotion, and he is the author of numerous books, including The Emotional Brain, and his latest masterpiece, The Deep History of Ourselves: The 4 Billion Year Story of How We Got Conscious Brains. Joe, it’s great to have you on the show.

Dr. Joseph LeDoux: My pleasure.

Dr. Stieg: Joe, can you tell me what role does consciousness play in my individual or human survival?

Dr. LeDoux: Well, our survival is based on our current existence and where we may be going. And humans have created a world that no other animal has been able to do. We’ve modified our environment to meet our needs and satisfy our wins. I mean, other animals can build little constructions, and nests that birds build and so forth. But we’ve done amazing things with buildings, change the landscape, and created art and music. So our conscious minds have given us things that no other species can even envision much less create. And so it’s one of our most wonderful talents, greatest achievements as a species.

Dr. Stieg: Obviously emotions and behavior are linked, but they’re also separate kind of neural networks, neural pathways. So how are they separate and how are they interrelated?

Dr. LeDoux: Well, it’s a good question. So the stimulus out in the world, say the snake at your feet will go into your visual system, picked up by the eyes, be transmitted through the brain, to the visual cortex, for example. The visual cortex will send that signal to the amygdala, and at the same time, to the prefrontal cortex. So the pathway to the amygdala controls those behavioral and physiological responses that evolution has given us to protect us in those situations. And the pathway to the prefrontal cortex gives us the conception of what it is that’s happening, how that impacts you and what the consequences for you might be. And as a result of that complex but automatic process, you end up with the experience of fear. So those are separate, but now once your heart is racing, and your palms are sweating, and hormones are being released, and your body is tense and freezing. All of that sends signals back to the brain. Um, that then for example, will increase brain arousal, cause all kinds of changes in the brain that your conscious mind will also be picking up on. We know the prefrontal processes involved in all this or closely related to what’s been called working memory. So working memory is monitoring your, your brain states and your body states and so forth. Getting information, not just about the stimulus, but also about what’s going on in the rest of your brain and body — by monitoring your behaviors, see yourself responding in a certain way. That’s feedback that you can bring into working memory as well, to help you choose how you’re responding, you know, what to do.

Dr. Stieg: This is one of the things I find most fascinating is even during your response to a particular stimulus, you can make that split second in your behavior.

Dr. Stieg:  What specific systems and brain regions are involved in anxiety processing and then how we think about it in terms of pharmacologic control?

Dr. LeDoux: So the, the starting point will be to think about this is that anxiety like fear is a cognitive construction, the conscious experience in your prefrontal cortex. In order to bring these things under control, we need to address the prefrontal cortex and its cognitions that preconsciously generate our conscious experiences of fear and anxiety. For example, memory, we need memory for those precognitions. We’ve got to, in other words, come to some kind of a way to control the hippocampus in a better way. There are many other circuits that would also be involved in all of this, but if we approach the problem as a starting point, I think we can begin to conceptualize how other circuits interact with those.

Dr. Stieg: A lot of this seems to be linked to the ability to be aware of our past our present, but most uniquely our ability to think about the future and plan for the future.

Dr. LeDoux: Well, Kierkegaard described anxiety as you know, the price we pay for freedom. What I would say is anxiety is the price we pay for having a prefrontal cortex that can envision the future. We can anticipate things. So I know other animals can, including in our own demise and bad outcomes that can happen to us. And that is the core thing about anxiety. It’s a thought about the future. Now, in order to have those thoughts about the future, we have to engage in what’s called mental time travel to the future. Now mental time travel is easiest to understand in terms of the past, every time you recollect something that happened to you, you’re retrieving episodic memories, memories about personal experiences you’ve had, and these are stored in the hippocampus. And when they’re retrieved, they’re brought into the prefrontal cortex to be experienced. So when you have that episodic memory in the prefrontal cortex, through your conscious mechanisms, you’re able to now revisit, actually feel yourself in that past experience. And so mental time travel to the future is like visiting something in the past. But instead you’re imagining it happening in the future. Now in both cases, the it’s not the future or the past, but your future and your past. So these are very personal subjective experiences that we can travel to because of the kind of brain we have.

Dr. Stieg: Joe, can you define what consciousness is?

Dr. LeDoux: Well, consciousness is your awareness of yourself or your environment. It’s subjective in the sense that it’s you that’s having the experience and it’s that sense that you own your mental states, who else could be having this thought but me, and this is put into relief by certain psychiatric or neurological patients in whom they seem to lose their ownership of their mental states. They still have content, but they don’t feel it belongs to them.

Dr. Stieg: As a neuroscientist. Do you put it into a spectrum?

Dr. LeDoux: So that’s, what’s called creature consciousness. The ability to be alive and cycle through sleep and wake and responsive to stimulate. Yes, that is part of what we’re talking about is the experiential thing, magic mojo, that rides on top of all of that, that’s subjective a feeling that this belongs to you that it’s used, that’s generating those experiences. I’ve also been a little bit fascinated by these reports of near death experiences. You know, people that have their heart stops, but then there’s the sort of fake near death experience for astronauts when they hit five GS and spin and they lose consciousness for 20 seconds and then they come back to life what they’re experiencing.

Dr. LeDoux: So I think of consciousness as a kind of mental simulation. It’s a kind of prediction and it’s not like it’s tied to the outside world. It’s a model that we generate based on the outside inputs. What we see is as determined as much by what we know about the world, as about what’s actually coming in, I see a red leaf out my window here, but I’m interpreting that and seeing it before I’ve, um, before I’ve completely built it up as visual perception. I’ve cognitively defined what it was based on a prediction. So in a situation like near death, I think we’re just making — the brain is doing its best to make sense out of that and making models and predictions about what’s going on. And that’s what happens. So every, every conscious state is preceded by non-conscious state. And it’s a non-conscious states that are building the content. And your actual experience is just sort of like, um, it’s like a narration that’s come out of that non-conscious information.

Dr. Stieg: Is there a particular part of the brain that we can refer to when we’re thinking about this non-conscious process?

Dr. LeDoux: Let’s say you’re looking at a picture of an apple and that stimulus is in your visual cortex, but your visual cortex only has the visual properties of the outlet. In order to know what you’re looking at and recognize it as an apple, those visual properties have to be integrated somehow with memory because without memory, those patterns are meaningless. Then that means that the visual and the memory properties have to be integrated. In other words, it’s bringing those two mental states, the visual state and the memory state together and combining them into one cognition that is the pre-conscious state that generates the narration that becomes conscious.

Dr. Stieg: Once there’s a stimulus, a conscious state can create either a fear response or the anxiety response. Are fear and anxiety related?

Dr. LeDoux: Yes, very related. They’re both responses to threats. Um, in the case of fear, the threat is immediately present. In the case of anxiety, it’s a worry about something that hasn’t happened yet. Then let’s say you have a person who’s anxious about alien abduction. That person is just as anxious as a person that is anxious about their mortgage or  a virus. Uh, it has nothing to do with, uh, the reality of the anxiety. In other words, should it, should the person be anxious with alien abduction? No, not because it can’t happen, but that’s not what it’s about. It’s about a mental understanding that the person has about their life. In a situation of danger, though, you see the snake, you are now afraid of it because you’ve constructed the cognitive, uh, model that there’s a snake and that’s going to harm me. But that quickly morphs into worry about whether the snake will bite you.

Dr. LeDoux: And if it bites you, will you be able to get to a doctor, will they have the antidote, and so on? So anxiety flows naturally from fear, but anxiety can also be a trigger of a fear. In other words, by once you’re anxious about something — things in the world that would normally not necessarily be dangerous at the moment become triggers that make you afraid. And that makes you more anxious. So fear and anxiety are just looping between each other. And you could say, well, they’re really the same thing. And they are, except that it’s useful to make the distinction because that first response has a different circuitry than the second response: fear. The fear circuitry are the circuits that are activated by the threat. The trigger, the amygdala response and the prefrontal response are separate from the circuits that generate the, um, uh, the worry response.

Dr. Stieg: Anxiety is probably one of the leading causes for people to go visit a psychiatrist. They want to control their anxiety. It doesn’t seem as though the medications that we’ve developed up to this point have been terribly effective because the number of visits remains relatively high. So what, what do you suggest, or what do you think we need to be doing in terms of rethinking our pharmacologic approach to the treatment of anxiety? I guess I’ll add, where does cognitive behavioral therapy play into this?

Dr. LeDoux:  Pharmacological approaches have their history in coming out of behaviorism. So you have a bunch of scientists who are now working for pharmaceutical industries, trained in behavioral methods to study animal behavior. And so these scientists then develop procedures to study. Well, what happens when we put a rat in a dangerous situation and give it one of these compounds and test to see what happens. Let’s say you have an animal in a big open area and you put him in the center, he’ll run to the side because you have some protection from the side. So that’s a natural response of a rat or a mouse to being in an open space. If you give the animal, the drug and they stayed in the open area a little bit longer, you would say, well, it’s, it’s less afraid. Therefore, when we give that drug to a person, the person should be less afraid. But unfortunately, uh, the drugs are not very effective at making people less fearful and anxious. And why is that? Well, how could you ever change something as complicated as a mental state, in a human, by developing a drug in an animal that’s changing its behavior. It’s the confusion of the conflation of the systems that control behavioral and physiological responses in animals and us with the system that controls and constructs our complex cognitive understanding of our world and our life that generate fear. So a person say on a, uh, SSRI, serotonin reuptake inhibitor, might find it uh, let’s say the person has social anxiety. She might find it easier to go to the party. Behaviorally, in other words, she’s less timid, but when gets there, she’s still anxious. So if the psychiatrist had said, well, that, this is called an antianxiety drug. It’s not going to really make you less anxious. What it’s going to do is reduce your behavioral timidity. You’ve been anxious all your life. You may be anxious the rest of your life, but the drug may be able to help you cope with it, but it won’t change your anxiety itself. It may tone it down. And I think that’s, that’s kind of what the medications do. It’s like you go to a restaurant — when we used to go to restaurants — and the music is too loud and someone says, can you turn the music down? The music goes down. It becomes less irritating, but it’s still the same music. And that’s, I think how the drugs are acting on anxiety. They tone down, they turned down the level, but they don’t make it go away. In fact, some psychiatrists say that, uh, benzodiazepines, SSRIs, it’s not a specific attack on anxiety it’s and perhaps use the medication as not a cure, but as a way to cope with aspects of it that free up the other aspects.

Dr. LeDoux: So basically there are three systems in the brain that need to be changed in order to bring this stuff under control. One is you need to change. You need to attain the amygdala, reduce the behavioral and physiological outputs by either a medication or some kind of exposure therapy. Second, you need to tame the hippocampus where we have our explicit memories and beliefs about situations. Once we’ve done that, then the brain would be ready for good, old fashioned talk therapy. But if you don’t do those things in that sequence, um, then you aren’t prepared to be able to have a relaxed conversation about it

Dr. Stieg: Well, what about a drug that would either amp up or turn down the frontal lobe’s control over the amygdala and the hippocampus? Is that a possibility?

Dr. LeDoux: In an emotional situation, you’ve got a lot more going on than in the simple situation of looking at an apple. So the problem with your suggestion is that you don’t want to like turn down the entire cognitive system, and there’s no way to turn down the emotion part of that, because it’s just one, it’s just the same old part. It’s just doing a different thing with different information in an emotional situation. So I think we have to approach the change of the way the person can seize and understand their lives with regular talk therapy. But if you don’t tame the hippocampus first, then the beliefs and memories will invade and take it back. And if you don’t tame the amygdala, then the arousal will bring it all back. But if you only, if you only do the talk therapy, then that’s not going to help either because the other things will bring it back.

Dr. Stieg: Where do you think research on consciousness is going? Where do you, where do you think the next big breakthrough in the Nobel prize is going to be?

Dr. LeDoux: I’m not sure we’re anywhere near a Nobel prize in consciousness research, but the field is really ramped up in the last two decades. And it’s been at a kind of Renaissance of, of activity. Consciousness was sort of poo-pooed by neuroscientists for a long time, but now it’s becoming a more acceptable area of research and there’s been tremendous progress, but we need to, there’s almost too much research now and too many ideas.

Dr. Stieg: Is it because of the utility now of functional MRI? The Human Connectome Study and all that?

Dr. LeDoux:  It’s been amazing, you know, without fMRI, we wouldn’t have consciousness research right now, but that doesn’t mean that fMRI is the answer, but it certainly has gotten us part of the way. Basically you can learn a lot about the underpinnings of consciousness, which is necessary to understand consciousness itself. You got to understand those non-conscious processes that take you all the way to the goal line. And then you got to get across the goal line, but let’s get to the goal line first.

Dr. Stieg: So functional MRI can possibly help us identify the area of the brain that is important in a particular response or emotion, but then we’re going to need neuroscientists like you to look at the cells and the neurotransmitters and all that, right?

Dr. LeDoux:  I think they need philosophers and psychologists, especially, I think we are making progress. And it’s important as we collect data though, to ask, what does it really mean? And do we have the right conception? Because we get stuck in conceptual ruts and then the field is coming to a stall because we think we know what we’re doing, but if you really don’t understand what you’re looking for in the brain, you’ll never find it.

Dr. Stieg: Joe, as always, it’s been fantastic talking with you about what role they play in our consciousness and in our response to external stimuli such as fear. The conversation clearly points out to me that we’ve got a long way to go. And we’re really at a basic fundamental level in terms of our understanding. Great talking with you.

Dr. LeDoux: Thank you very much. It’s been a pleasure.