The Wisdom Paradox Read online

  Language is a cultural tool of incredible complexity and versatility. We often think of language as a means of communication. It is certainly that, but also much more. As we will discuss later, language is a means of conceptualization, of information compression, which enables us to represent complex information in compact codes. The brain machinery of language is highly distributed. As already mentioned, the meaning of object words (nouns) is stored in the left temporal lobe close to the visual cortex. That makes sense: Our mental representations of objects are based mostly on vision. The meaning of action words (verbs) is stored in the left frontal lobe close to the motor cortex. That also makes sense: Our mental representations of skilled movements involve those parts of the brain. Complex statements establishing relations between things are processed in the part of the left hemisphere where the temporal and parietal lobes come together—the left angular gyrus.

  Damage to these different parts of the brain will impair language in different ways, to use technical language, will produce different forms of aphasia, depending on where exactly in the left hemisphere it occurs. The causes of such damage vary: It could be stroke, head injury, or dementia. Indeed a particular form of language disorder, called anomia (loss of the use of words), is among the early symptoms of Alzheimer’s disease.

  But the right hemisphere is not left out of the action, either. As Christiane Amanpour’s voice rises to an urgent crescendo, it is the right hemisphere that detects the feeling of alarm conveyed by it. While the left hemisphere is in charge of most aspects of language in an adult brain, the right hemisphere is in charge of prosody. Prosody is information conveyed through verbal communication, but by means of intonation and inflection rather than by the literal meaning of words. It is what we call the “emotional tone.” (Dysfunction of the right hemisphere, as in Asperger’s syndrome, impairs the ability to process such “extralinguistic” contextual information. As a result, the patient’s behavior becomes mechanical, awkward, and often inappropriate, devoid of subtlety and fluidity.)

  Your dog has also sensed the urgency in the commentator’s voice (I don’t know with which hemisphere of his brain; hemispheric specialization has not been extensively studied in animals, although I have advocated such research for years) and began to growl. You recognize his canine growl, as opposed to any other sound in the environment, without taking your eyes off the TV screen. This was also accomplished through the left hemisphere, the left temporal lobe to be precise. Damage to the left temporal lobe produces not only aphasia, but also an inability to identify environmental sounds by their sources. This often overlooked condition is called auditory associative agnosia.

  Meanwhile, the visual cortex has been busy all along taking in the images on the television screen. Since you are in excellent neurological health, you easily take in information both from the left and the right half of the screen. You can do this because both hemispheres of your brain are working just fine, and the connection between them, a thick bundle of pathways called the corpus callosum (the latter word from Latin for callus), is intact. Damage to one hemisphere, particularly to the parietal lobe, often produces visual hemiinattention or even outright visual hemineglect. A patient afflicted with visual hemiinattention has difficulty attending to the information appearing in one half of the visual field—the half opposite to the side of brain damage. Visual hemineglect is even more severe than visual hemiinattention, one half of the visual field being completely ignored. Left visual hemiinattention or hemineglect (caused by damage to the right hemisphere) is usually much more severe than right visual hemiinattention or hemineglect (caused by damage to the left hemisphere).

  What’s even more interesting is that the patient is often unaware of left hemineglect or left hemiinattention. Such unawareness of deficit is itself a neurological symptom, usually caused by damage to the right hemisphere, and it is called anosognosia. Anosognosia is a source of all kinds of hazards, since the patient may be unaware of any deficit, not just hemineglect or hemiinattention. Imagine a driver afflicted with visual hemiinattention yet unaware of it. Unfortunately, this is not that uncommon in patients who have suffered a stroke in the right hemisphere. Despite the fact that it will be obvious to everybody else around, any attempt to convince the patient of the impairment will likely meet with failure. This is often called “denial,” but strictly speaking it is not. “Denial” implies an intact ability to know and a choice not to know. In anosognosia the capacity for knowing one’s own deficit is genuinely lacking due to brain damage. A patient will often insist on driving and carrying on with other activities that imperil himself and other people.

  In a highly protective environment, the effects of hemineglect or hemiinattention may be more comical than tragic. I will never forget an elderly man in a nursing home who suffered a right-hemispheric stroke with left hemineglect and ranted indignantly about the conspiracy of nurses. He was furious that his fellow patient sitting across from him at the cafeteria table was getting a steak, while all he was getting was mashed potato—an outrageous inequity indeed. The key to this apparent injustice was simple. The kitchen personnel had the habit of placing the steak on the left side of the tray and the mashed potato on the right side of the tray. So the old gentleman always saw the potato on right side of his tray and the steak on left side of the tray in front of the fellow sitting opposite him. And it was impossible to get the old man to comprehend that the problem was within and not outside, until the nurses learned to flip the tray in front of him. The patient remained convinced that he was a victim of dirty tricks and that nothing was wrong with him. Yet aside from his dinnertime ire, he was the happiest, goluckiest patient on the unit.

  Unlike the old man, your visual fields are in good order, left, right, and center. So you are able to scan the whole television screen and follow the important details. The ability to scan a detail-rich visual scene extracting important information from wherever it may appear in the environment is ensured by a region of the frontal lobes called the frontal eye-fields. They are firing away as you are relating Christiane Amanpour’s commentary to the images on the screen.

  As you do so, you are processing the specific visual images on the screen. You recognize them as representations of meaningful objects: houses, cars, trees . . . and unfortunately tanks, guns, and such. This throws into action another part of the visual cortex, your visual association cortex, mostly in the left hemisphere, as already mentioned.

  You also see faces—smiling faces, anxious faces, happy faces, angry faces, faces of unknown people in a faraway country. As you stare at them, trying to have a glimpse into the minds behind the faces, the temporal lobe of your right hemisphere is hard at work. This part of the brain has been shown to be in charge of facial recognition.

  But curiously, the face of Christiane Amanpour is processed mostly by your left hemisphere. A peculiar division of labor takes place in the brain. The right hemisphere is better at dealing with novel, unfamiliar information, and the left hemisphere is better at dealing with familiar information. This is true for most kinds of information, so that the faces of strangers are processed on the right and the faces of public figures, or family members and friends whom you encounter all the time, are processed on the left.

  With the “Breaking News” report in progress, a map appears in the upper right corner of the TV screen to highlight the place of the events. This brings into action your spatial, parietal lobe on its junction with the visual, occipital lobe. Neuroscientists distinguish between the “what” and the “where” visual systems in the brain. The “what” system, on the junction of the occipital and temporal lobes, is in charge of object recognition. The “where” system, on the junction of the occipital and parietal lobes, is in charge of location information.

  As the visual images and the reporter’s narrative blend seamlessly into a story, you are not even cognizant of which information comes in through the eye and which information comes through the ear. It all becomes intertwined and interwoven in you
r mind. This is because your heteromodal association cortex is doing its job properly and efficiently. This part of the brain is in charge of putting together streams of information coming in through different senses and integrating them into one neural multimedia theater. Among the most recent to develop in evolution, this part of the brain is particularly vulnerable to Alzheimer’s disease and other dementias.

  This is the third time the region is in the news this week, you are saying to yourself as you follow the Breaking News. In order to reach this conclusion, you must be able to relate the current events as presented in the news today with your memories of the news over the past few days. You have just successfully employed your recent memory, for which the hippocampi are particularly important. Hippocampi are also particularly vulnerable in Alzheimer’s disease. In fact, Mony de Leon and his colleagues at the Aging and Dementia Research Center of New York University’s School of Medicine have developed innovative techniques using fine measurements of the hippocampal size based on magnetic resonance imaging (MRI) as an early predictor of vulnerability to Alzheimer’s disease.

  The good news brought to us by state-of-the-art neuroscience research is that new neurons tend to develop in the hippocampi. What’s particularly exciting is that the rate at which the new neurons appear in the hippocampi can be influenced by cognitive activities and by exercising your brain. We’ll explore this in later chapters.

  As the news is being delivered, you are trying to figure out what will happen in the conflict-ridden region next. A game of prediction, like a game of chess, is a tricky business. You need to assess the overall context and to put yourself in the place of each of the main players. You need to plausibly surmise what they think of the situation. Napoleon understood this very well, when he admonished his marshals: In anticipating the adversary’s move, don’t expect him to do what you consider to be his optimal move. Try to figure out what he considers his optimal move from his own perspective, given his own history, and with the information likely to be available to him, not to you. The ability to put yourself in someone else’s “mental shoes” is called by cognitive neuroscientists the capacity to form the theory of mind.

  These complex abilities—to plan, to anticipate, to form the theory of mind—are all very young in evolutionary terms. They are present only in humans in a developed form, and one might say, they are what makes us human. All these complex functions, which we have begun to understand only recently, are controlled by the prefrontal cortex. I wrote about it extensively in my earlier book, The Executive Brain. The youngest and most complex part of the human brain, it is also the last to develop. It is fully developed only by the age of eighteen or possibly even as late as thirty. This validates the custom shared by most modern cultures, according to which the age of eighteen or thereabout is the age of legal maturity, and the eligibility for highest elective offices requires an even more advanced age. The prefrontal cortex is very vulnerable in a broad range of neurological and psychiatric disorders, such as dementia, schizophrenia, or traumatic brain injury. Dysfunction of the prefrontal cortex has also been implicated in such less devastating but nonetheless disruptive conditions as Attention-Deficit/Hyperactivity Disorder and Tourette’s syndrome.

  Your own prefrontal cortex was nudged out of its slumber the moment you began to play the game of crystal ball, trying to make political predictions. And so was your anterior cingulate cortex, a brain structure closely linked to the prefrontal cortex, which is particularly active in situations of uncertainty.

  But you know your limitations and can spend only so much time playing the game of crystal ball, a game that even Napoleon eventually lost. Your attention is drifting and you are beginning to feel sleepy. That means that your ascending activating reticular formation, a very important structure in charge of keeping the brain aroused and alert, has had it for now.

  You yawn, stretch, and turn off the TV set. The thought of taking your dog for a walk crosses your mind, but then you decide to stick around and refill your drink. Your hypothalamus, amygdala, and orbitofrontal cortex have all lit up—the mechanisms of basic gratification. . . . Life is that simple on a Saturday afternoon.

  2

  SEASONS OF THE BRAIN

  What Happens to the Brain Happens to the Mind

  Now that we are done with this casual review of your brain in action, stand back and think (your brain again). If activities as trivial as a day-in, day-out morning routine or watching the news on television are so demanding of brain resources, can you imagine the brain machinery behind the complex professional activities of a physician or an engineer, the intellectual rigor of a mathematician or a chess player, or the creative surge of a violinist or a dancer? Cognitive neuroscience is only beginning to address these issues, but it is no longer possible to think or talk about the mind without the brain, or about the brain without the mind.

  As a typical reader of this book, you are not a brain scientist, but you are a brain user, a consumer of brainpower, so to speak. And the odds are that you have not been particularly inquisitive about the inner workings of your brain. This is a curious phenomenon, and it concerns all of the human body, not just the brain. Ironically, most of us generally do not care about our body, as long as it leaves us alone, does not ache, hurt, itch, or malfunction, and allows us to feel good. If Johnny contracts hepatitis A from bad oysters, he does not go to the doctor because his liver enzymes are elevated and viral titers are up; he goes because he feels lousy and tired, and because his face and eyeballs have turned yellow—not a highly valued trait on the dating circuit.

  Even though Johnny does not particularly care to know about the inner workings of his body, he accepts the general premise that how he feels depends on, among other things, the condition of his liver, which has to be dealt with in order for Johnny to feel good again and regain a desirable complexion. But when it comes to the mind-brain relationship, the closeness of this link does not seem to have trickled into the public awareness yet. The general public is only beginning to appreciate the fact that any assault on the brain will affect your mind.

  But is the inverse true? Can we improve the quality of the mind by improving the function of the brain? If the answer to this question is “yes,” then Johnny should start learning how to take care of his brain, just as, in the last few decades, he has embraced the notions of healthy physical living (raw oysters notwithstanding). In this book, I will argue that what happens to one’s brain as one ages depends to a great extent on what one does with it at a younger age. I will also argue that it may be possible to improve one’s mind by improving one’s brain even at an advanced age. I will discuss how this happens in everyday life and what can be done to accomplish it better in a more structured manner.

  First, though, we need to understand the natural processes in the brain throughout the life span. “Seasons of the mind” or seasons of the brain is, of course, a metaphor, but not too far-fetched a metaphor. The brain and the mind go through stages in the course of a lifetime. Like the seasons of the year, the seasons of the mind are not separated by clear-cut absolute boundaries, but morph gradually and seamlessly into one another. So any attempt to link these boundaries to precise chronology is a matter of convention rather than of real biological discontinuities. Just as the change between seasons may vary from year to year (early summer one year, late spring another year), so too the exact timing of transition from one “season of the mind” to the next varies somewhat from person to person. To complicate matters even further, not all aspects of the mind and the brain move through the stages in perfect synchrony. This means that how exactly you set the boundaries between the stages depends to a large degree on your choice of the criteria. Unlike the four seasons of the year, it is common to speak about three seasons of the brain: development, maturity, and aging.

  Developing Brain

  The first season, the season of development, is when the main cognitive abilities and skills are formed, which is characterized by dramatic changes in the br
ain. This season begins before we are born and extends into the third decade of our life. Brain development is a complex and multifaceted process. It starts with neurogenesis , the birth of neurons, which are the brain cells most directly involved in information processing, and their migration, finding their proper places in the complex organization of the brain. For the most part, neurogenesis occurs during gestation, at somewhat different times for different brain structures. It was thought until recently that neurogenesis ran its course and ground to a complete halt sometime during gestation and the first few years of life. By that time, most brain structures have acquired their recognizable shape. Today we know, however, that neurogenesis continues throughout the lifetime, albeit not as vigorously as during the early period.

  As the neurons are born and migrate to their proper locations in the brain, connections between neurons begin to develop. These connections, formed as protrusions emanating from the neuron bodies, are called axons and dendrites. They begin to develop during gestation, and the dendrites begin to sprout through the process called arborization. This process culminates during the first years of life.

  Synapses, the tiny interfaces between the dendrites and axons emanating from different neurons, are critical for communication between neurons. Their formation is called synaptogenesis and its time course varies considerably for different parts of the brain. In the visual cortex, for instance, most of synaptogenesis is complete by the end of the first few years of life. By contrast, the synaptogenesis of the prefrontal cortex extends well into late adolescence and early adulthood.