p CHAPTER 1 What Are the Origins of Brain and Behavior? Focus on Disorders: Closed Head Injury The Evolution of Brain and Behavior Defining Brain and Behavior Origin of Brain Cells and Brains Classification Systems What Is the Brain? Evolution of Animals with Nervous Systems How Is the Nervous System Structured? The Chordate Nervous System What Is Behavior? Human Evolution Perspectives on Brain and Humans: Members of the Primate Order Behavior Australopithecus: Our Distant Ancestor Aristotle and Mind The First Humans Descartes and Dualism The Evolution of the Human Brain Descartes’s Legacy Focus on Disorders: Linking Brain Function Studying Brain and Behavior to Brain Disease in Modern Humans Darwin and Materialism Human Brain-Size Comparisons Darwin’s Legacy Culture Focus on Disorders: Learning Disabilities Crandall/The Image Works Micrograph: Oliver Meckes/Ottawa/Photo Researchers p Twelve years ago, I survived a serious head injury. In the sec- significant event of my lifetime. The catastrophic effect of ond it took for my car to crash head-on, my life was perma- my injury was such that I was shattered and then remolded nently changed, and I became another statistic in what has by the experience, and I emerged from it a profoundly been called “the silent epidemic.” different person with a different set of convictions, values, During the next months, my family and I began to un- and priorities. Above all, I have learned that there is no derstand something of the reality of the experience of head limit to the power of faith, hope, and love. With these, I injury. I had begun the painful task of recognizing and ac- made the journey out of the shadows into a larger, brighter cepting my physical, mental, and emotional deficits. I world than the one I had left behind before my injury. couldn’t taste or smell. I couldn’t read even the simplest (Linge, 1990) sentence without forgetting the beginning before I got to the end. I had a hair-trigger temper that could ignite instantly his description of what it is like to be brain injured into rage over the most trivial incident. During the first year, I could not take too much stimu- was written by Fred Linge, a clinical psychologist lation from other people. My brain would simply overload, Twith a degree in brain research. (For an explanation and I would have to go off into my room to get away. Noise of how the brain can be injured in an accident, see was hard for me to take, and I wanted the place to be kept “Closed Head Injury” on page 2.) In the years after his in- quiet, which was an impossibility in a small house with jury, Linge made an immense journey. He traveled from a three youngsters in it. I remember laying down some impos- time before the car crash, when he gave less thought to sible rules for all of us. For example, I made rules that the relation between his brain and his behavior than he everybody had to be in bed by 9:30 PM, that all lights had to be out, and that no noise of any kind was permitted after did to the way in which he dressed. At the end of the jour- that time. No TV, radios, or talking was allowed. Eventually ney, thoughts about his brain and his behavior dominated the whole family was in an uproar. his life. He became a consultant and advisor to many peo- Two years after my injury, I wrote a short article: ple who also had suffered brain injury. “What Does It Feel Like to Be Brain Damaged?” At that Most of you are like Fred Linge before he took that time, I was still intensely focusing on myself and my own journey. Your brain does its work so efficiently and unob- struggle. (Every head-injured survivor I have met seems to trusively that you hardly give it any thought. You may be go through this stage of narcissistic preoccupation, which creates a necessary shield to protect them from the painful unaware that the human brain has hundreds of parts, each realities of the situation until they have a chance to heal.) of which participates in certain tasks. You may have no I had very little sense of anything beyond the material world knowledge that the brain changes as you age, as you un- and could only write about things that could be described dergo major life events, and even as you engage in seem- in factual terms. I wrote, for example, about my various im- ingly trivial behaviors, such as reading the words on this pairments and how I learned to compensate for them by a page. In learning about the origins of the universe, the variety of methods. world, and human beings, you may have encountered no At this point in my life, I began to involve myself with other brain-damaged people. This came about in part after mention of the brain and its relation to behavior. Yet, if you the publication of my article. To my surprise, it was reprinted ever had first-hand experience with brain damage, you, in many different publications, copied, and handed out to too, would be confronted with the workings of this most thousands of survivors and families. It brought me an enor- wonderful and complex machine. mous outpouring of letters, phone calls, and personal visits The purpose of this book is to take you on a journey that continue to this day. Many were struggling as I had strug- not unlike the one that Fred Linge took. Through it you, gled, with no diagnosis, no planning, no rehabilitation, and too, will come to understand the link between brain and most of all, no hope. The far-ranging effects of head injury on the survivor’s behavior. Of course, we do not ask that you experience life and that of his or her family cannot be overemphasized. brain damage to undertake this journey. The road that we In my own case I realize that it was for me the single most offer is simply one of information and discovery. Yet, along I 1 2 I CHAPTER 1 Closed Head Injury Focus on Disorders Closed head injury results from a (A) (B) blow to the head that subjects the A variety of mechanical brain to a variety of forces. First, the forces cause closed head injuries as a result of a force exerted on the skull at the site blow to the head. of the blow causes bruising (contu- sion) known as a “coup.” Second, the blow may force the brain The damage at the site of impact is called a coup (shown in pink). against the opposite side of the Direction of blow Direction of blow skull, producing an additional bruise called a “countercoup” (see The pressure resulting from a coup may produce a countercoup on the opposite the accompanying illustration). side of the brain (shown in blue). Third, the movement of the brain Movement of the brain may shear nerve fibers, causing microscopic lesions, especially may cause a twisting or shearing of in frontal and temporal lobes. Blood trapped nerve fibers, causing microscopic in the skull (hematoma) and swelling (edema) cause pressure on the brain. lesions. Such lesions may be found throughout the brain, but they are most common in the Shading (pink and blue) indicates regions of the brain most frequently damaged in closed head injury. A blow can frontal and temporal lobes. Fourth, the bruises and strains produce a contusion both at the site of impact and at the caused by the impact may produce bleeding (hemorrhage). opposite side of the brain owing to compression of the Because the blood is trapped within the skull, it acts as a brain against the front (A) or back (B) of the skull. growing mass (hematoma), which exerts pressure on sur- rounding brain regions. Finally, like blows to other parts of severe because the head is moving when the blow is struck, the body, blows to the brain produce swelling (edema). This thereby increasing the velocity of the impact. swelling, which is a collection of fluid in and around dam- The diffuse effects of closed head injuries make diagno- aged tissue, is another source of pressure on the brain. sis very difficult, which is why these kinds of injuries have People who sustain closed head injury often lose con- been collectively called a “silent epidemic.” Victims of se- sciousness because the injury affects fibers in lower parts of vere closed head injury can suffer serious repercussions in the brain that are associated with waking. The severity of their everyday lives. Like Fred Linge, many have difficulty re- coma can indicate the severity of the injury. Closed head in- turning to their former levels of functioning, including carry- juries resulting from motor vehicle accidents are particularly ing out their previous jobs. it, you will find that much of the evidence that we have In this chapter, we answer the question, What are the about the brain and behavior comes from the study of origins of brain and behavior? We begin by defining both changes in people who have suffered brain injury. At the the brain and behavior and outlining the nervous system’s same time, we are also learning more and more about basic structure. We then look at how people through his- how the brain works when we are healthy. This emerging tory have viewed the relation between brain and behavior, knowledge is changing how we think about ourselves, starting with the mentalistic perspective of Aristotle and how we structure education and our social interactions, progressing to the biological perspective of today.