Consciousness, Self, and the Prefrontal Cortex

cartesian-theater

There is a basic question that must be addressed when pondering the nature of consciousness, and that is: why have consciousness at all? The brain processes a great deal of information below the level of conscious awareness, from visual to auditory to tactile, and then the integration of all of these before they can be brought into conscious awareness. Yet conscious awareness itself seems much more limited in the amount of information that it can handle at a time—5 to 9 “chunks” of information, at a time, it would seem. So why rely on conscious awareness as heavily as we do? It certainly seems, at least from this angle, much less able than non-conscious processing—yet, given its apparent efficacy in raising humanity to the heights of culture and insight that we enjoy today, it surely has something essential to offer us.

The prefrontal cortex is the latest structure to appear in the evolution of the brain, and is the structure that shows the greatest development between humans and our closest biological relatives. Furthermore, it is known to mediate a great deal of the abilities considered distinctly human, such as planning, reflection, and empathy, all of which apparently require conscious awareness. Surprisingly, however, a vast abundance of the projections that the prefrontal cortex sends back to more primitive, sub-cortical structures are inhibitory—they function largely to suppress activity in these regions. In fact, this has led several researchers to rethink the concept of free will and, somewhat amusingly, refer to it rather as “free won’t,” in that we are mainly choosing what not to do, of all of the responses recommended by sub-cortical structures. And this is where we might find a reason for conscious awareness.

Consciousness relies on a crucial ingredient for dealing with the world in the way that the prefrontal cortex specializes in doing: it removes behavior from the moment-to-moment sensory perceptions incessantly presenting themselves to sub-cortical brain regions. Instead of constantly responding to each and every stimulus as it comes in, consciousness introduces a disconnect that allows reality apart from oneself to be treated as perceived, and thus distinct from the self and manipulable. Non-conscious responses don’t require perception in the same way that conscious processes do. In order to consciously ponder a course of action while planning, you need a virtual representation to work with, and in order to do that, you need some distance between yourself and the object being represented. Every day perceptions such as the visual field in front of you may function in a very similar manner: a stimulus presents itself, is processed by sub-cortical structures, and then a course of action is offered up to conscious awareness to be chosen or discarded by conscious reflection. There is a whiff of “opponent processing” going on in this narrative, something that comes up a lot in systems biology: two structures working in opposite directions in order to better center around a single desired outcome. Non-conscious, sub-cortical processing is largely reactive, leading to sometimes extreme, reflexive responses; conscious prefrontal processing, on the other hand, divorced from the constant demands of the environment, is more receptive to multiple courses of action, but can sometimes leave us unable to settle on an alternative. With the two of these working with opposing aims, however, behavior that is reactive enough to survive, but receptive enough to be a functioning member of society, can be attained.

This is far from a coherent theory or hypothesis, but the parallels between the roles of sub-cortical and non-conscious processes on the one hand, and prefrontal and conscious processes on the other, along with the connections between the two, are surely going to be important in mapping human consciousness.

In Search of Memory

A few weeks ago, I read Eric Kandel’s In Search of Memory. It was different from the books that I normally post about here, as it is an autobiography with the emergence of modern neurobiology woven in, rather than an argument for this or that perspective. But I am a neurobiologist at heart and an aspiring scientist at the very beginning of my career, so I couldn’t resist:

memory

Eric Kandel won the nobel prize in the year 2000 for his pioneering work on the molecular mechanisms of memory formation and storage. In this book, Kandel lays down the path of his life, professional and otherwise, from his earliest days in Vienna, just before World War II, up through his acceptance of the nobel prize in Stockholm, just a few years ago. His book will be of interest to biologists, philosophers, psychologists and laymen alike. The material is presented in the order that it was first discovered and assumes no prior knowledge, leaving no bars to entry for this exciting journey. All the same, weathered experimentalists will surely enjoy the ride that is the birth of this new science, from single-cell recordings in hippocampal cells, to the neural networks of Aplysia, to the beginnings of the differentiation of  the neural substrates for unconscious vs conscious information processing.

And a fun fact for those who are, like me, still trying to break into this field: What was Eric Kandel, nobel laureate in biology, studying in his Junior year of college? None other than Northern European History. He didn’t set foot in a lab until medical school, when he was entranced by the promises of psychoanalytic theory. I think we’ll be ok.

Finally, for those of you who wonder what I am doing when I am not reading or writing about consciousness (or wonder why I post so scarcely now!), I am now excitedly spending the majority of my time in the BRAIN Lab at Washington University in St. Louis on a summer research fellowship studying up on neurogenetics (i.e., how genetic variation influences how our brains respond to our environment and modulates risk for psychopathology). Check us out!

[Off Topic] A Scanner Darkly

[This is going to be a little different than the books I normally recommend on here, but I think that it will be worth your time.]

I recently finished Philip K. Dick’s A Scanner Darkly, and I highly recommend it. Keep in mind that I rarely read fiction books, so if I can get myself to finish it, then it’s really something that I enjoyed a great deal.

The book takes you on a trip through the eyes of Bob Arctor, a drug addict and undercover narcotics agent, as he deals with the illicit drug Substance D. To avoid too much in the way of spoilers, I’ll pique your neuroscientific interests with the following, and leave it at that:

Substance D doesn’t just alter the mind, it splits it in two…

Memory and Personal Identity

Today in metaphysics I had to write up an impromptu response to the question: “Is memory important to Personal Identity?” I only had thirty minutes to write and not much time to prepare, so it’s a little rough, but I am nonetheless satisfied with what resulted, so I’ve reprinted it here:

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Memory is not vitally important to personal identity. This is not to say that it is not useful to our everyday determination of “who’s who,” more on that later, but we can show that it is possible to maintain personal identity without maintaining memory.

Consider the case of Tom, or case 1. Tom is about to be tortured. But the torturer, being a slightly nice guy, proposes the following: before torturing Tom, he will wipe all of Tom’s memories. Should this make Tom feel any better? “Of course not,” I would expect Tom to reply, “I’ll still be tortured, I just won’t remember that it’s still me who was tortured!” So we are not making the situation any better—we are actually making it worse! Not only are we going to torture Tom, we are also going to turn him into an amnesiac! If this case is persuasive, then we have shown that memory is not necessary for personal identity.

But I think we can go one step further and show that it is not sufficient either. Consider case 2: Exactly the same as before, except this time we will not merely erase Tom’s memories, but instead transfer them to another body, say, Jane’s body. Now, who would Tom, pre-memory transfer, want us to torture, Tom’s body or Jane’s body? I think that, thinking only of himself, he should want us to torture Jane’s body, and here’s why: this case is no different from the first. If removal of memory is not enough to remove personal identity, as the case 1 seems to show, then how could implantation of memory create a person? If it were able to do so, then we would have two “Toms” at the end of the procedure: one amnesiac Tom in Tom’s body and one “normal” Tom in Jane’s body—but this seems to be obviously mistaken, Tom can only be in one place at a time! So which Tom is illusory? Well, if we stick with our judgment for case 1, then it seems we have to say that the “Tom” in Jane’s body is the illusory one. It’s not really Tom, Jane just thinks that she is Tom. Tom is still in Tom’s original body. If all of the preceding is true, then we have shown that memory is neither necessary nor sufficient for personal identity.

At this point, it would be prudent to evaluate just what it is that we are saying, and just what we are not saying. The preceding argument aims to show that memory is not important from a metaphysical standpoint—but this says nothing about the epistemic standpoint. In real life, memory is often all that we have to go on for determining personal identity. How do I know that I am the same person as I was last week? Because I have the memories of what I did last week! If we agree with the preceding argument, though, it would seem as if we were contradicting ourselves. We cannot determine our own identity based solely on our memories. Well, okay, maybe we can’t, for all we know, some mad scientist  implanted some false memories into my brain while I slept, and I am not who I think I am, this is not outside the realm of possibility. But it seems pretty unlikely—so, inferring to the best explanation, that barring unusual circumstances memory goes hand-in-hand with personal identity, I conclude that I am most likely the same person as my memory tells me I was last week. It’s not certain, but it is very likely. It’s important to note here, though, that these are all epistemic worries. They tell us nothing about the metaphysics of personal identity. I can use memory as a good “indicator” of personal identity, so in that sense it is very important to our conception of personal identity, but that does not mean that the two are inextricably linked. As an analogy, if I hear a dog bark, I usually infer  that a dog is nearby, but for all I know someone is merely playing a recording of a dog’s bark and there is, in fact, no dog nearby. Personal identity refers to the dog, and the recording of a bark is the memory of Tom in Jane’s body.

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There’s a technical point about memory that I did not have time to address in my original response, but which I want to bring up here. In order for something to really be a memory, it has to stand in a causal relation to the event that it recalls—that is, the event that it recalls has to itself be what caused the memory to exist. So in this sense, I probably have many things that I would call “memories” in my head that are not truly memories. Perhaps I am misremembering something, or perhaps I have heard a story of my childhood so many times that, even though unbeknownst to me my own memory of the event is gone, I have recreated the scene in sufficient detail for me to be able to picture it vividly. On this definition of memory, Jane never really had memories of Tom’s life. They felt like memories to Jane, but since they were not caused by the events in Tom’s life, but rather by the torturer’s memory implantation, they are not, in this strict sense, true memories. If you were to adopt this more nuanced view of memory, then a memory theory of personal identity may be more plausible. Unfortunately though, you can still show, as per case 1, that memory is not necessary for personal identity.

Personal Identity, Brains and Fission Cases

When it comes to personal identity, the following question needs answering: what does it take for person A at time 1 to be the very same person as person B at time 2? Perhaps more clearly, right now I am sitting in front of my laptop, typing this post. In, say, ten minutes, there will be a person sitting in front of this laptop, publishing this post. What has to be true of that person for us to say that that person, ten minutes from now, is me? Now, it seems to me that this is a rather strange question for us to be asking, and it may be that we are simply confusing ourselves when we ask it—but let us assume for the present discussion that it is a coherent question to ask, as many contemporary philosophers certainly have, so that we may examine one answer that has been suggested.

The brain view, a slightly more refined version of the body view, says that in order for us to determine whether or not we have the same person at two different time points, we need to determine whether or not they have the same brain (accordingly, the body view says that we need to track the body—but this, for obvious reasons, can lead us astray). Neuroscience tells us quite assuredly that the brain is, in some way, the seat of what makes a person a person. Inside the brain lies all of the machinery required for memory, learning, personality, and all of the other traits and abilities that ordinarily allow us to identify the people around us as being who we think they are. The problem, however, with simply examining these surface-level features is that they can be mimicked, they can be replicated in a copy, leading us to the false conclusion that the copy is the real thing, just as if we were merely to examine outward body features. If we track the causal history of the brain itself, however, we should be able to figure out who is who in a more concrete manner.

So far, so good. We have what seems to be a good thesis: track the brain, track the person. Now we would like to refine the view even further. Is the whole brain necessary for personal identity, or only part of it? We know that in many respects the brain is redundant, having two more-or-less copies of each cortical structure—might we only need half of a brain to maintain personal identity? We are not necessarily constrained by specifics here, so let us make a simplifying assumption: each cortical hemisphere is indeed an exact mirror image of the opposite cortical hemisphere (there seems to be nothing in nature that points to this being impossible).

Now consider the following thought experiments: At time 1, Fred is a normal, healthy person. At time 2, he suffers a sudden, catastrophic loss of one of his cortical hemispheres. We now need to ask ourselves, is Fred-2 the same person as Fred-1? Common sense seems to tell us that he is, so perhaps on the brain view one hemisphere is indeed sufficient for maintaining personal identity. Now let us start over: at time 2, instead of Fred simply losing half of his brain, imagine that, instead, his brain is removed from his body, half of it is destroyed, and then the remaining half is implanted into the brainless body of Steve. After sufficient recovery from the operation, Steve’s body wakes back up—but who has woken up? On the brain view from before, we would have to say that Fred wakes up in Steve’s body. After all, it is the brain, not the body, that truly matters here. Alright, one more twist. Imagine this time that at time 2, Fred’s brain is again removed from his body, but this time the left half of brain is implanted into one brainless body, while the right half is now implanted into a separate brainless body. I have provided a schematic below to clarify the situation:

lY4c1

 

 

We have one body, Lefty, and another body, Righty (the names merely allow us to keep track of which body gets which half of the brain). After sufficient time for recovery, both bodies awaken. Now we again have to ask: who is waking up in each body? We have three options here, it would seem: 1) Fred, the same Fred as Fred-1, is waking up in both bodies; 2) Lefty is Fred-1, but Righty is not (or vice-versa); or 3) Neither of these people who wake up are Fred-1, Fred-1 died when the transplant took place. It we remain faithful to our previous conclusions, it would seem that we have to go with choice 1: both Lefty and Righty are equally Fred-1. But this can’t possibly be the case! How can Fred be in two spatial locations at the same time? Is he experiencing both bodies’ perceptions at the same time? If so, how? This simply seems to be impossible, and I am inclined to agree with this. Okay, how about option two? Perhaps Fred-1 is now in Lefty’s body—but wait, what reason do we have for him being in Lefty’s body versus Righty’s body? Both bodies, as per our simplifying assumption, have exactly the same half of a brain as the other. So much for option two. We’re now left with a final choice: neither Lefty nor Righty are Fred-1. Fred-1 is dead, no longer in existence.

But if we accept this conclusion, and it seems that we must, what does this say for our first two cases? Is Fred-2 no longer Fred-1 simply because he has lost half of his brain? There’s something that tells us that he has to be the same person. Obviously he is not exactly the same, he now has half of a brain, but intuitions seems to maintain that he is nonetheless still the same person—are we wrong?

I am not sure where exactly I stand on this issue at the moment, but I do have one thought that I think is promising. If the brain is truly duplicated in each hemisphere, but only one is needed for personhood, might there have been two people in Fred-1’s body (that is, one per hemisphere)? We may want to redefine a “person” as two of these “hemisphere-persons” in this case, which leaves us with the following: Fred-1 did not die, but half of him did. Fred-1, in the strictest sense, no longer exists, but part of him does. Returning to the final case, then, none of our original options really suffice. Instead, we would say that half of Fred-1 is in Lefty, while half of Fred-1 is in Righty.

This may not seem to be too strange of a conclusion, seeing that each body indeed has half of a brain, but when it comes to identity, it is at least a little weird. We like to think of personal identity as a 1:1 relation. You either have a person or you don’t, nothing in between. It’s not the case that after ten years of life, I am only 80% me. No, I am still me—the same person as I was before, even if my desires, beliefs, etc. have changed a little or a lot in the intervening time period. Should we re-evaluate this intuitive answer?

 

 

Conversations on Consciousness

convoncons

Since the spring semester is now in full swing, it has been increasingly difficult for me to devote the necessary time to a full-length treatment of consciousness as I would like. This in mind, I picked up a copy of Susan Blackmore’s Conversations on Consciousness the other day, and I have not regretted it. It serves as an informal introduction to several competing theories and views on the scientific study of the brain and conscious experience. The set-up of the book is simple: interviews with the researchers/philosophers themselves explaining their theories in their own, colloquial way. Add to this a few questions on free will and the fate of consciousness after death, and you get twenty of the most interesting conversations that I’ve ever had the pleasure to read. They allow, among other things, the chance to see these researchers as actual people, and not simply as objective reporters of experimental results as happens far too often.

I have only one complaint about the book, which you may have guessed given the author, Susan Blackmore. Put simply, Blackmore endorses a few very fringe (and some, myself included, would say absurd) ideas about the nature of consciousness. Normally, this would not be an issue—everyone is entitled to their own opinions, and I often disagree with the authors that I read. The complaint comes, however, in the questions that Blackmore chooses to ask her interviewees. The book is accompanied by the sub-script, “What the Best Minds Think about the Brain, Free Will, and What it Means to be Human.” At times, though, it seems like it would read more accurately as, “What the Best Minds Think about My Ideas about the Brain, Free Will, and What it Means to be Human.” This is not over-riding, and most of the time the book stays true to its stated purpose (I thank the interviewees for most of this, they do a good job sticking to what they believe are the real issues), but it is, at times, distracting. It is not enough to knock this down as a great book, well worth reading, but it is something that should be noted, nonetheless.

I would like to give this five out of five stars—it was great fun to read—but the above complaint makes me unable to do so. That said, I would give the interviewees five out of five stars and Blackmore four out of five stars, so let’s say that the book as a whole gets four and a half out of five stars.

Brief Thoughts on the Analogy with Vitalism

It is sometimes asserted that consciousness and many of its aspects are illusory. Some of this, I believe, may turn out to be true. For example, our naive conception of conscious will seems to be at least partially illusory (see here and here for my views on that). Some, however, claim that even such fundamental notions as our sense of self are illusory, finally claiming that consciousness as a whole will one day be explained away as an illusion. I, as you may have guessed, take serious issue with this claim.

A common line of argument taken to support the claim draws an analogy between the present situation and the endeavor to explain life some hundred years ago. There were, in those days, the vitalists. These were the theorists who could not imagine that dead matter and its interactions could account for all that there is to complex life—there had to be something extra, some elan vital, or life force, underlying all of this. Even if we explain heredity, reproduction, growth, etc., we will still be missing something—namely life itself. We now know that they were wrong, dead wrong, and that, in fact, there is simply dead matter interacting in specific ways that leads to the formation of complex, living organisms.

Now take the assertion made by many contemporary philosophers of mind: even if we explain vision, intelligence, emotion, etc. (i.e., the so-called “easy problems” of consciousness), then we will still be missing something—namely consciousness itself. If we explain all of those things that can be worked out computationally, then we will be missing the very thing that we sought to explain in the first place: subjective, conscious minds. But is this necessarily the case? Might consciousness simply fade away the more and more we know about these other processes? Maybe consciousness is simply the elan vital of philosophy of mind, say proponents of this analogy.

This could not be further from the truth. When it came to explaining life, a higher-level property such as the elan vital was postulated to account for something that we did not know the cause of: the difference between living and dead objects. When it comes to consciousness, we are not postulating something above and beyond what we already know. In the words of Descartes, “I think, therefore I am.” His dualism may have been misguided, but he was spot on in stating that there is nothing that we know with more certainty than that we are conscious, that we are our own self. In this way, the analogy is deeply flawed. Something can only be explained away if it was postulated to explain something that we know to be true. Consciousness, however, was never postulated. Instead, it was the very phenomenon that we set out to explain. We may be wrong about the details, and in all likelihood we are, but we are not, as a matter of fact, wrong when we state that we are conscious beings, that consciousness is a real, existing phenomenon that begs explanation in its own right.

The Rediscovery of the Mind

I finished reading Searle’s The Rediscovery of the Mind last week, and it was quite an exciting read, to say the least. In a field full of confusing, frustrating, and downright baffling theories and assertions, a little bit of no-nonsense pseudo-polemic writing can be a breath of fresh air, and this book is just that.

At it’s heart, this book is an argument for Searle’s own theory of mind: Biological Naturalism, which can be summed up as saying that the brain, under the right conditions, gives rise to conscious experience in the same way that water, under the right conditions, gives rise to liquidity. Even more fundamentally, however, Searle uses this book to remind us all of what we are really doing when we propose theories of mind, hopefully in a way that helps us realize the obvious mistakes we make all too often.

Searle closes the book with a near perfect set of guidelines, which I have re-printed below, because, even if you aren’t able to read the book in its entirety, I think that you should consider them:

In spite of our modern arrogance about how much we know, in spite of the assurance and universality of our science, where the mind is concerned we are characteristically confused and in disagreement. Like the proverbial blind men and the elephant, we grasp onto some alleged feature and pronounce it the essence of the mental. ‘There are invisible sentences in there!’ (the language of thought). ‘There is a computer program in there!’ (cognitivism). ‘There are only causal relations in there!’ (functionalism). ‘There is nothing in there!’ (eliminativism). And so, depressingly, on.

Just as bad, we let our research methods dictate the subject matter, rather than the converse. Like the drunk who loses his car keys in the dark bushes but looks for them under the streetlight, ‘because the light is better here,’ we try to find out how humans might resemble our computational models rather than trying to figure out how the conscious human mind actually works. I am frequently asked, ‘But how could you study consciousness scientifically? How could there be a theory?”

I do not believe there is any simple or single path to the rediscovery of the mind. Some rough guidelines are:

First, we ought to stop saying things that are obviously false. The serious acceptance of this maxim might revolutionize the study of the mind.

Second, we ought to keep reminding ourselves of what we know for sure. For example, we know for sue that inside our skulls there is a brain, sometimes it is conscious, and brain processes cause consciousness in all its forms.

Third, we ought to keep asking ourselves what actual facts in the world are supposed to correspond to the claims we make about the mind. It does not mater whether ‘true’ means corresponds to the facts, because ‘corresponds to the facts’ does mean corresponds to the facts, and any discipline that aims to describe the world is aims for this correspondence. If you keep asking yourself this question in the light of the knowledge that the brain is the only thing in there, and the brain causes consciousness, I believe you will come up with the results I have reached in this chapter, and indeed many of the results I have come up with in this book.

But that is only to take a first step on the road back to the mind. A fourth and final guideline is that we need to rediscover the social character of the mind.

If this closing passage appeals to you, I would recommend that you read this book in its entirety. I certainly found it well worth the effort (and it is an effort). Five out of five stars—I’ll be revisiting this many times.