The Brain

by Gary L Wenk

  What is pseudoscience?

  In addition to drugs and herbals that are marketed using pseudoscientific logic, there are almost as many nondrug interventions for your brain that also lack any shred of scientific proof. These interventions usually invoke the actions of some mystical force that physicists have yet to discover. The fact that these interventions lack any scientific support does not deter desperate people from seeking them out and, most important, paying for them. Craniosacral therapy, ear candling, magnet therapy, crystal healing, cupping, Rolfing, neurolinguistic programming, psychokinesis, and primal therapy are just a few of the frequently mentioned examples of completely ineffective interventions. In addition, “energy medicines,” which involve “laying on of the hands,” or various types of hand waving above the body, or any of the numerous naturopathic practices, provide no medical relief beyond the placebo effect.

  What is the placebo effect?

  Much has been written about the value of the placebo effect in the practice of medicine, but how this effect emerges and whether it can be controlled are issues that are not yet understood. Essentially, scientists have analyzed the effect based on results of placebo-controlled studies of actual drugs or have compared only the effects of a placebo against the consequences of no treatment at all. Their findings have been intriguing, if still largely inconclusive. However, in one area of study that is not directly related to an actual treatment, the findings are more definitive. Numerous meta-analyses (which are combined analyses of other researchers’ data) have shown that the perception of pain can be statistically demonstrated to be influenced by our minds. Scientists refer to this as the emergent property of our brains. This influence of our thoughts and expectations on how we experience pain is a true placebo effect.

  Perhaps one particular study has shown us the location of the placebo effect. Scientists measured pain perception in two groups of people, devout practicing Catholics and professed atheists and agnostics, while they viewed an image of the Virgin Mary or the painting of Lady with an Ermine, by Leonardo da Vinci. The devout Catholics perceived electrical pulses to their hand as being less painful when they looked at the Virgin Mary than when they looked at the da Vinci work. In contrast, the atheists and agnostics derived no pain relief while viewing either picture. Magnetic resonance imaging (MRI) scans demonstrated that the Catholics’ pain relief was associated with greatly increased brain activity in their right bottom-lateral frontal cortex. This brain region is believed to be involved in controlling our emotional response to sensory stimuli, such as pain.

  Other studies using brain imaging techniques to show correlations between brain activity and the extent of reported placebo effects have demonstrated that some people show greater placebo responses than others, but that everyone appears to be capable of having such a response. There is also increasing proof that the use of placebos might benefit people with Parkinson’s disease, depression, and anxiety. In the future, with better testing measures, scientists likely will demonstrate how the placebo effect influences many aspects of our health. In short, the placebo effect is real; we simply do not understand entirely how it works, but the evidence thus far is truly remarkable, particularly with regard to pain. Some people are able to block incoming pain signals or alter how they are perceived. And without a doubt, your mind can make the experience of pain more or less agonizing depending on how you feel—for example, if you are fatigued, anxious, fearful, or bored, then pain becomes more intolerable. Recent studies have identified specific sets of genes, referred to as the “Placebome” that may contribute to the placebo effect. In the future, a detailed analysis of your genetic makeup may allow your doctor to predict clinical outcomes better and potentially allow the judicial use of “effective” placebos.

  Although we do not yet know how the placebo effect works in the brain to influence this process, we do know that it comes into play, and sometimes in surprising ways. For example, the color of the pill you take influences your expectation of what it will do to you. Obviously, pills can be made any color, yet most people like their antianxiety pills to be blue or pink or some other soft, warm color; they prefer their powerful anticancer pills to be red or brightly colored. Americans do not like black or brown pills, in contrast to the preference of people in the United Kingdom or Europe. Thus, almost everything that Americans buy over the counter is a small white, round pill. Yet big pills, or pills with odd shapes, also are assumed to be more powerful, or just simply better, than tiny round pills. Sometimes, a simple change in color or shape restores a drug’s ability to produce a placebo effect. And sometimes, the effect comes from the pill-taking regimen. For example, you expect that when you are instructed to take a medication only during a full moon, or only every other Thursday, it must be extremely, almost mystically, effective. Herbalists often take advantage of this concept by recommending odd or excessive dosages of peculiar-looking pills or foul-smelling potions. We all want to believe that the pills we take will help us feel and function better; fortunately, thanks to the poorly understood phenomenon of the placebo effect, we do sometimes, but only for a while, benefit even from the most bogus of potions and pills. If all you are getting is a sugar pill, then does it really matter whether you are fooled into believing the lie? Possibly; it depends on the cost of the sugar pills and the risk one assumes by not taking a medicine of proven effectiveness in a timely fashion for a medical condition. Finally, nothing has ever been proven to enhance brain function; only caloric restriction can slow brain aging. Just think about how much money you are going to save by not wasting it on unproven alternative therapies and by consuming much less food.

  6

  HOW DOES MY BRAIN ACCOMPLISH SO MUCH?

  I originally considered beginning this book in the traditional style with a discussion about the basics of brain anatomy. I decided not to follow that tradition because I wanted you to become excited about what your brain can do before investigating the precise anatomical structures that achieve those amazing feats of learning and sleeping and love.

  Let us start our exploration of basic brain science by drilling into the top of your head! The tip of the drill has traveled only about one half inch through your scalp and skull, and we immediately encounter three layers of protective membranes called meninges; their names are the dura (the outermost layer), arachnoid (the middle layer), and pia mater (the innermost layer). A person has meningitis when these membranes become infected. Between the arachnoid and pia layers is a space filled with a clear, colorless liquid. This liquid is cerebrospinal fluid and is essentially blood that has been filtered of cells and most proteins. Freshly produced cerebrospinal fluid is constantly rinsing your brain. The amount of fluid produced is impressive: every ounce of cerebrospinal fluid is completely replaced about four times every day. If the constant flow of cerebrospinal fluid is impeded in any way, the fluid will quickly accumulate inside your skull, thereby increasing intracranial pressure, pressing the brain against the inside of the skull, squeezing the small blood vessels that feed the brain until they close, and ultimately leading to the death of brain tissue. This condition is called hydrocephalus; it occurs more often in infants than older adults and can be fatal if not corrected immediately. Your skull has a fixed volume; this fact often places your brain in serious peril.

  The brain is submerged in an ocean of cerebrospinal fluid inside your skull. Why go to all of this trouble to keep the brain afloat? The answer is related to the fact that your big brain weighs a lot: about three pounds. However, when floating in the cerebrospinal fluid, the net weight of your brain is equivalent to a mass of only 25 grams—that is less than an ounce of beer. How is this possible? If you have ever experienced floating in the ocean, the salt water made you buoyant and you floated easily on the surface with very little effort, as though you weighed much less. The salty cerebrospinal fluid provides the same benefit; it allows the brain to maintain its density and shape without being crushed by its own weight. This same principle of buoyancy allows seag
oing mammals, such as whales, to become very large; however, once they have left the salt-water ocean, they quickly succumb to the consequences of their own weight. If your brain were resting on a table, its own weight would quickly crush the small blood vessels supplying it, killing the cells on the bottom of the brain.

  In addition, by floating within the skull, bathed in cerebrospinal fluid, the brain is protected from injury when the head is jolted around quickly. Unfortunately, when the head is violently displaced due to a car accident or a blow to the head associated with playing football, soccer, or field hockey, this fluid buffer cannot prevent the brain from colliding with the inner surface of the skull. If the brain does collide against the skull, the outer layer of the brain, the cortex, can become attached by scar tissue to the inner surface of the skull, leading to the death of outer layers of the cortex. Repeated violent blows to the head, such as those experienced by boxers and other athletes with a history of repetitive brain trauma, ultimately leads to large sections of the cortex becoming stuck to the inner surface of the skull. If the injury to the cortex continues and becomes widespread, the resulting loss in brain function is called dementia pugilistica; in the 1920s these symptoms were called the punch-drunk syndrome. Today, due to the notoriety professional athletes have drawn to this condition, this progressive degenerative disease is referred to as chronic traumatic encephalopathy. The damage to the cortex associated with this injury may spread to involve nearby subcortical brain areas that are responsible for movement and sensory processing, producing symptoms such as stiffness, slowness, and walking or balance problems. When this happens, the result is Parkinson’s pugilistica. The boxer Muhammad Ali demonstrated many of the symptoms of both dementia pugilistica and Parkinson’s pugilistica.

  As we continue to drill into your head, the next thing we encounter is your cortex. The cortex is a thin sheet of cells that covers the brain; it is responsible for the extraordinary abilities that you depend upon for normal everyday life, such as thinking, feeling, seeing, hearing, and touch. Given the importance of the cortex for so many abilities that truly define our species, this chapter will focus primarily upon its structure and function. If you imagine yourself miniaturized and standing on the surface of your brain, the cortical surface appears like a series of rolling hills, which are called gyri, and valleys, which are called sulci. Anatomists have divided the brain into four separate lobes according to the location of specific and very deep sulci. The lobes were given the names frontal, temporal, occipital, and parietal (derived from the names of the skull bones that overlie the lobes). Overall, your brain, as well as the brain of your cat and the mouse it is waiting to catch, is organized so that the back half receives incoming sensory information and then processes it into your own very personal experience of the here and now. The front half of your brain, the frontal lobes, is responsible for planning your movements, usually in response to some important incoming sensory stimulus, such as someone’s voice telling you that it is time for dinner. The lobes in the back half of your brain process the voice that you hear, smell the aroma of food cooking, feel a craving for food as your blood sugar levels fall, and sense that it is late in the day and the sun is setting and the room is getting darker; thus, it must be dinnertime. This information is funneled into the front of your brain, which then makes a decision to move the front end of your feeding tube toward the smell and the voice to obtain a reward—food and survival for another day! Your brain has successfully performed its most important tasks for the day, and it now can rest with you in front of the television.

  How does your brain manage all of this every day? Neurons—billions of them. Your brain, as well as the brain of your dog and the flea living on its back, is composed mostly of cells called neurons that interact both electrically and chemically with one another. Your brain also contains some supporting cells called glia. The average adult human brain contains about 90 billion neurons, give or take. A typical neuron possesses a cell body, dendrites, and a long single axon. Dendrites are thin filaments that extend away from the cell body, often branching multiple times, giving rise to a complex tree of dendritic branches. An axon is a special narrow extension that projects away from the cell body and travels for a rather long distance. Some axons can extend for almost three feet in humans. The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon. An individual neuron will communicate via its dendrites and axon with about 7,000 other neurons. The connections are far more complicated than those of your local telephone network.

  If you were to scoop out a very small section of cortex, you would find it packed with neurons, glia, blood vessels, and very little else. Most of the space between neurons is filled with astrocytes, a type of glia. Astrocytes have another more notorious role; astrocyte tumors make up the majority of brain tumors. Astrocyte tumors are categorized as either low-grade, which are usually localized and grow slowly, or high-grade, which grow rapidly. Most astrocyte tumors in children are low grade; in adults, the majority are, unfortunately, high grade. Tumors that consist of only neurons are quite uncommon and, when they do occur, tend to be less aggressive. The contrast between these two types of tumors, glial versus neuronal, is likely related to the fact that the normal function of glia is to multiply in number following certain types of injury or infection, while neurons are genetically programmed to never multiply once they have achieved adult status.

  The brain is densely packed with blood vessels. Neurons are never more than a few millimeters away from one because a constant supply of oxygen-rich blood is critical for normal brain function. Blood flow to the brain, about three cups per minute, is carefully regulated because too much or too little blood flow can be harmful to the brain. Normal brain function is rapidly lost if the supply of oxygen is interrupted for even a few moments. Sometimes, the temporary loss of blood supply to the brain can produce quite bizarre experiences, such as near-death visits to heaven.

  Are near-death visits to heaven real?

  No, they most certainly are not. Unless you want them to be. Near-death visits to the spiritual realm usually begin in a hospital emergency or operating room and are associated with the failure of normal heart function due to trauma, extended seizures, or cardiac arrest. When blood flow to the brain slows down, the supply of oxygen to the billions of individual neurons falls quickly. When the supply of oxygen drops, even just a little, 60% of the brain’s dopamine is very quickly converted into an entirely different molecule called 3-MT. Until a few years ago most textbooks stated that 3-MT was completely inactive in the brain. Our understanding of the actions of 3-MT in the brain improved when neuroscientists discovered that 3-MT acts in the same way as many hallucinogens, such as LSD and ecstasy. Consider this scenario: just as the blood flow to a patient’s brain is decreasing, the brain is spontaneously producing very high levels of a powerful hallucinogen. What might that feel like? People who have survived such near-death experiences often report floating through a blissful spiritual world that is full of love. People who have used LSD and ecstasy report a very similar emotional and sensory experience. Thus, the spiritual, pleasant, loving near-death experiences due to elevated levels of 3-MT are probably a consequence of the reduced blood flow to the brain. The mythical hallucinations associated with near-death experiences, and the ease with which we believe them to be true, demonstrate how vulnerable our sense of reality is to imbalances in brain chemistry.

  How do nutrients and drugs get into my brain?

  Astrocytes carefully control what is able to cross from blood to brain. Astrocytes are a critical component of your “blood–brain barrier.” The blood–brain barrier permits the easy entry of only a few substances into the brain. Fat-soluble substances can enter the brain easily. Very small molecules, particularly if they do not carry an electrical charge, usually get through the blood–brain barrier. The brain actively imports the nutrients it requires from your diet through the blood–brain barrier. Some regions of the brain lack any b
lood–brain barrier. The barrier does not form in these brain regions so that your brain can monitor levels of specific chemicals, such as the presence of sugar in the blood. As you will see later, the brain is only capable of sensing the presence of sugar, actually glucose, in the blood; it cannot sense the levels of proteins or fats in the blood. The ways in which the brain controls eating behaviors will be discussed later.

  The blood–brain barrier is often the Achilles heel of so many drugs that might offer something beneficial to the brain—the drugs never get into the brain. Your brain rests comfortably behind a biological firewall called the blood–brain barrier. Every day you consume chemicals that would produce significant changes in brain function—if they could get across this barrier. There are times, of course, when you might prefer that drugs could get across this barrier more easily. Only about 5% of all of the drugs currently available by prescription can cross the blood–brain barrier. Today, drugs that are designed to treat disorders of brain function are specifically designed to cross this barrier. Obviously, if a drug cannot enter the brain, it is going to have a difficult time influencing brain function. One recent case illustrates this point. Prevagen is a commercial product currently being aggressively marketed as a memory supplement; its main ingredient is apoaequorin, an incredibly large, highly water-soluble molecule that is an excellent example of a molecule that cannot cross the blood–brain barrier. Any benefit it provides to memory is, therefore, due to the placebo effect. In addition, the U.S. Food and Drug Administration (FDA) recently issued a warning that Prevagen may produce serious side effects that are not due to the placebo effect.