Books >> The Modular Brain:
Chapter 1
At home I have a diagram taken from a children's encyclopedia from the 1930s. It's labeled "The Central Control Station of Your Body," and shows a cutaway view of a human head containing tiny rooms, occupied by one or more men dressed up in business suits fashionable at the time.
In one room, a man is sitting at a desk talking into one of those two-piece telephones, the earphone held in his hand and the mouthpiece sitting in front of him on the desk. Written above this scene is the phrase, "Manager of Speech." Toward the back of the brain, a small box houses a man scanning pictures on a desk. He is the "Receiver of the Camera Pictures," forwarded to him over “air tubes" from a room farthest to the front containing four men dressed in sailor uniforms and pulling on rigs and pulleys controlling the eye (they are identified as the "Camera Operators"). At the center of the cutaway head is a room larger than any of the others and occupied by three men sitting at a conference table (in line with the prevailing practices and prejudices of the time, only white men are depicted in charge of the "control stations"). This caption reads, "Brain Headquarters in the Cerebrum."
Altogether nine tiny boxes filled with men carrying out various tasks illustrate the workings of the brain. The caption for the diagram as a whole reads: "Imagine your brain as the executive branch of a big business. It is divided as you can see here into many departments. Seated at the big desk at the headquarters office is the General Manager--your Conscious Self--with telephone lines running to all departments."
Today it is easy to ridicule such a simplistic view of how the brain works. We don't experience ourselves as a "General Manager" issuing orders to members of a bureaucratic organization. Greeting a friend, for instance, doesn't seem to have anything in common with the process described in this fanciful diagram: 'Instantly you begin issuing orders: 'Tell the Speech Manager to say "Hello Johnny!" Tell the Leg Superintendent to stop walking at once! Tell the Arm Superintendent to stick out my hand right away and take Jones's hand! Tell the Face and Lips Superintendent to give this man a good big smile!'"
Rather, most of the "orders" issued and received within the body must be unconscious ones, since we are not aware of issuing them. Indeed, most of the operations of our brain take place outside of our conscious awareness, and on the whole that isn't such a bad thing. None of us would wish consciously to have to initiate every action, no matter how petty, or to be aware of even the most trivial of sensations.
But at the highest levels of our mind's operations, during those less pressured, more "philosophical" moments when we delve inward and explore the terrain of our own minds, we tend to encounter and experience a "self," a conscious controller who wills, remembers, decides to act, experiences emotions, feels pain, and simultaneously rejoices and fears for the future. And at such times we tend to subscribe to something similar to the General Manager in the diagram. But when we try to pin down this "self," this General Manager of the psyche, our experience is like trying to ensnare a fish that has caught our eye by reaching into a pellucid lake with our bare hands. We experience consciousness and awareness in ourselves, but have no way of conveying these experiences to others. It's not that we doubt--except in moments of intoxication, fever, or insanity--the reality and existence of our inner self, our "mind." It's just that, try as we might, we cannot pin it down in regard to its exact nature or location.
For centuries, the mind was treated as a mysterious, ethereal entity that could not be further inquired about and the brain, the originator of all thought, was either ignored altogether or treated as an inconvenient irrelevance. Such an attitude was at least partly based, I am convinced, on a kind of "turf battle." Traditionally, "why" questions (Why am I here? Why is the world the way it is?) have been asked by philosophers, and until very recently, few philosophers expressed any interest in learning about the brain. As a result, many of the most interesting questions were approached in a false and artificial way that turned off many people, myself included, who find philosophical questions fascinating and challenging.
In my elementary philosophy class, for instance, we spent hours debating whether a tree falling in a forest empty of people made any noise. The solution to this conundrum comes not from the use of syllogisms or other forms of reasoning, but from knowledge about the human ear's connections to the brain along the auditory pathway from the tympanic membrane to the medial geniculus in the midbrain, to the primary auditory area in the temporal lobe, and finally to the auditory association area, where the sound is recognized and identified. If the sound waves created by the falling tree fail to strike a tympanic membrane, or for some reason that message is not relayed onward to the brain, then no sound exists; since sound, by definition, requires an ear and a brain. Absent these, we have only waves of a certain frequency. Another much debated question has to do with the reality of space and time independent of the mind. The philosopher Immanuel Kant, who knew nothing about the brain, arrived intuitively at the conclusion brain scientists would reach two hundred years later. In The Critique of Pure Reason, published in 1781, he wrote that space and time corresponded not to “objective"realities existing independently of the mind (we would now say the brain) but are themselves categories created by the mind. He claimed we can have no knowledge of things as they are in themselves, existing in a strictly independent physical sense. This is because our senses construct our world for us and therefore do not present to the mind external independent realities but only perceptions. In essence, our "objective” world is a highly subjective one.
When I first encountered Kant I found his ideas appealing, even though it would be another decade before I confirmed that Kant was right when I encountered neurological and psychiatric patients who suffered from disabilities affecting their appreciation of space and time. Now, after twenty years studying the brain and writing eight other books about it, I think the time is right to explore some traditional philosophical questions in the light of what we have learned about the brain over the past several decades.
Consciousness, thought, memory, will, emotion - none of these has any independent outside reality other than in the context of the human brain. All are based on the brain's organization. This concept takes some getting used to at first. Few of us think of ourselves in terms of our brains. If we think about the brain at all, it is usually in a way similar to the way we think about the rest of our body. For instance, we may take up dietary approaches aimed at increasing our alertness or mental efficiency. To this extent the brain is just like every other organ composing the great "machine," the human body. But few of us equate ourselves with our brain. Yet a few moments spent with a person who has just suffered a stroke illustrates in a stark and vivid manner one of nature’s aphorisms: Change the brain, change the person. As a result of brain injury, the person is not the same person as before. Insofar as we can enter into the stroke victim's mental life - a task we will attempt at various points throughout this book - we encounter clear indications that perceptions, thoughts, and emotions are drastically different than before the brain injury. What's more, these differences are often unexpected, even bizarre. In the pages that follow, for instance, we will encounter a man who loses the ability to name animals but has no difficulty in naming inanimate objects; another who can recognize tools but not musical instruments. Such surprising impairments suggest that the brain is organized differently than was believed by most experts in the past. Who could have ever imagined, for instance, that the concept of size could exist independently within the brain, so that a person could lose the sense of whether an elephant is bigger than a mouse but remain normal in every other way? None of these strange and tragic impairments could have been predicted. Nor could we learn what they teach us about the reality formed by us in our brain by simply sitting around and thinking about them or discussing them with others. Logical analysis, reason, or the other methods favored by philosophers are little help here. Only patients with these impairments, many of them severely disabling and all of them tragic, can teach us how our brain constructs our individual and collective "reality.” Nature is the teacher, the patient “experiment,” and the human brain the classroom.
The Modular Brain describes recent discoveries about brain organization and what that means for our ideas about the nature of reality. Thus the book is in the tradition of exploring the "mind-body problem.” But I prefer to think of it as finding and identifying the General Manager depicted in our 1930s diagram, if he exists, or permanently firing him if he doesn't. Let's start with a quick overview of how we will proceed.
History provides three revolutionary insights into the relationship of the brain and the mind.
The first insight dates to the Greeks, specifically the physician and philosopher Hippocrates, who wrote:
Not only our pleasure, our joy and our laughter but also our sorrow, pain, grief and tears arise from the brain, and the brain alone. With it we think and understand, see and hear, and we discriminate between the ugly and the beautiful, between what is pleasant and what is unpleasant and between good and evil.
With his recognition of the brain as the seat of the mind, Hippocrates overthrew thousands of years of speculation favoring other bodily organs. (The Egyptians selected the liver; Aristotle held out for the heart, considering the brain little more than a cooling system for the blood.)
Two thousand years later, two early nineteenth-century European physicians, Paul Broca and Carl Wernicke, conducted or supervised autopsies of patients who during their lifetimes had suffered from aphasia, an impairment of their capacity to speak or understand language. Broca and Wernicke discovered areas of brain destruction in the left hemisphere of these patients. From this came the second revolutionary insight. Broca and Wernicke concluded that the left hemisphere mediated the production and understanding of spoken language. But their findings had a wider application than just language. In addition, they provided support for the view that the brain is not a homogeneous structure in which one part is equivalent to every other but, instead, is made up of special centers located at various locations in the two hemispheres .
Following on the discovery of the language centers came the discovery of the visual areas toward the back, hearing along the sides, and movement and sensation toward the front. Over the ensuing 120 years, neurologists and others have established additional correlations between structure and function.
The third revolution in our understanding of the brain extends back not more than a few decades, with much of the important work no more than a few years old. It evolved from the view that the brain is organized according to a hierarchical structure wherein the cerebral hemispheres, the most recent and highly evolved areas of the brain control those more ancient areas inherited pretty much unchanged from our evolutionary ancestors. While this view is still useful in its way, it ignores recent evidence that even such a seemingly straightforward function as vision is not at all a unitary process but involves separate parallel processes that working together, result in our visual experience.
The Modular Brain presents this new way of thinking about our mind and its relationship to our brain. It is organized into three sections.
First, we will examine what has been thought over the centuries and until very recently about the relationship of mind and brain. When we compare what we know about the brain now with the thoughts held by our predecessors, it's easy to become smug and assume we will soon learn everything there is to know about it. But that smugness soon disappears when we discover that although we have learned more about the brain in the last one hundred years than in all previously recorded history, we remain woefully ignorant of the bases for most of the operations of the brain. Moreover, as with physics after the introduction of quantum mechanics, neuroscience has still to come up with a unified theory that incorporates new discoveries about perception, thought, memory, and other brain processes. Sixty years ago, the Nobel prizewinning neuroanatomist Santiago Ramon y Cajal wrote: "In truth it is not possible, in our present state of knowledge, to formulate a definitive theory of the functional plan of the brain." If we emphasize the word definitive, then Cajal's sentence is as true today as the day he wrote it. But we have learned a lot in the intervening sixty years and can now offer some intriguing ideas about how our brain works.
In the second part, we will explore research leading up to this new truly revolutionary view of the brain's operation, modular theory. Briefly, this theory holds that our experience is not a matter of combining at one master site within the brain all of separate components into one central perception. As strange as it may sound, there is no master site, no center of convergence. For centuries we thought there had to be. Descartes and other philosophers referred to the brain's central coordinating area as a "homunculus," a personified character much like the General Manager, a kind of ghostlike figure later satirized by philosopher Gilbert Ryle as "the ghost in the machine." Ryle's point in referring to a ghost was, of course, that there is no evidence for such a central autonomous overseer within the brain. Besides, if such a creature existed, who would be monitoring him or her (or it)?
Wherever one looks in the brain - particularly the cerebral cortex, the overarching expansion of the brain that in size, complexity, and cell number differentiates us from all other living things - all brain cells and collections of brain cells communicate with other cells. This means that no "pontifical" cell or area holds sway over all others, nor do all areas of the brain "report" to an overall supervisory center. Thus, to betray my position at this early point in the game, the General Manager is a fictional character. And like all fictional characters he was created in order to fill a need within a story, in this case the early efforts to come up with a theory of how the brain works. But with a change in the plot, the characters too must yield place to different characters.
A theory based on multiple connections all operating simultaneously and in parallel has profound implications. "It implies that there is no cortical terminus, no final destination where the soul or consciousness, for example, may reside," according to Semir Zeki, a neuroscientist who has played a leading role in the research establishing the modular theory of brain organization.
Finally, we will explore what a modular organization of the brain means for our understanding of the human mind. If no "final terminus" or center exists within the brain, then who is this "me" encountered in moments of introspection? Most of us certainly don't inwardly experience ourselves as modular, but as singular and reasonably unified. Yet, as we shall see, important select aspects of ourselves may be altered or disappear altogether on the basis of damage to our brain (in other instances, of brain maldevelopment, they may never have evolved in the first place). If I am the result of the operation of a vast network of nerve cell interconnections, in which one cell may be influencing the response of any of the other 40 to 50 billion other cells, then what attitude should I take to my inner perception that I remain basically the same person throughout my life? What of free will? Philosophers have talked and debated for centuries about the unity of the personality, the nature of emotion, autonomy, and creativity. If you want to see how much they have accomplished and how little they agree about any of these terms, open a philosophy textbook. Not only is there no agreement, but many of the authors of these works seem to take a perverse pride in compiling long lists of what each separate philosopher thought and taught about even such seemingly elementary mental processes as perception. One reason for this smorgasbord approach to the mind is that--contrary to what most philosophers have written--perceiving and knowing are not separate processes, with one following the other like a bucket of water passed from hand to hand along a chain of firefighters, but one process. Vision, for instance, is not at all like a camera where the eye focuses light on the retina where a "picture" is taken and conveyed along the visual pathways to the brain for interpretation. Rather, the brain actively constructs what we "see," and we are at once camera, film, photographer, and picture. Just as no two pictures are ever exactly the same because of differences in one or the other of these elements, so too our brain, thanks to its modular organization, creates for each of us a unique "world picture."
In the pages that follow, we will explore the implications of modular theory for our ideas about memory, consciousness, free will, and personal identity. Modular theory helps us to set to rest many old puzzles and conundrums, but in the process creates some new and unique ones. To mention just one, artistic creativity involves some brain areas more than others; these areas also seem to be more developed in people proficient in the arts. Does this mean that artistic creativity is primarily an inherited trait, and that those with the "wrong" genes cannot hope to be artistically creative? Everyday observation seems to contradict that claim: Many artists have come from families with unremarkable artistic abilities. Yet artistic creativity of some artists at the highest levels seems to involve mental abilities (perfect pitch, writing and "listening" to musical compositions in one's head) that involve more than simple refinements on commonly encountered musical talents. Ravel was such an artist. His diaries describe his creative process and how that process broke down as a result of brain damage. Recent experiments employing PET scan studies of musicians have shed additional light on Ravel's creativity and modular brain mechanisms.
It is my hope that The Modular Brain will inspire general readers to consider the implications of this new theory.
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