In Sophocles’ (496-406 в.с.) play Oedipus the King, Oedipus finds his way blocked by the Sphinx, who threatens to kill him unless he can answer this riddle: “What walks on four legs in the morning, two legs at noon, and three legs in the evening?” Oedipus replies, “A human,” and is allowed to pass, because a person crawls as an infant, walks as an adult, and uses a cane when old. The Sphinx’s riddle is the riddle of human nature, and as time passes Oedipus comes to understand that it has a deeper meaning: “What is a human?” The deeper question in the riddle confounds Oedipus and remains unanswered to this day. The object of this book is to pursue the answer in the place where it should be logically found: the brain.
What Is the Brain?
People knew what the brain looked like long before they had any idea of what it did. Very early in human history, hunters must have noticed that all animals have a brain and that the brains of different animals, including humans, although varying gready in size, look quite similar. Within the past 2000 years, anatomists began producing drawings of the brain and naming some of its distinctive parts without knowing what function the brain or its parts performed. We will begin this chapter with a description of the brain and some of its major parts and will then consider some major insights into the functions of the brain.
The term neuropsychology in its English version originated quite recently, in part because it represented a new approach to studying the brain. According to Daryl Bruce, it was first used by Canadian physician William Osier in his early-twentieth-century textbook, which was a standard medical reference of the time. It later appeared as a subtitle to Canadian psychologist Donald O. Hebb’s 1949 treatise on brain function, The Organization of Behavior: A Neuropsychological Theory.
Although Hebb neither defined nor used the word in the text itself, he probably intended it to represent a multidisciplinary focus of scientists who believed that an understanding of human brain function was central to understanding human behavior. By 1957, the term had become a recognized designation for a subfield of the neurosciences.
Heinrich Kluver, an American investigator into the neural basis of vision, wrote in the preface to his Behavior Mechanism in Monkeys that the book would be of interest to neuropsychologists and others. (Kluver had not used the term in the 1933 preface to the same book.) In 1960, it appeared in the title of a widely read collection of writings by American psychologist Karl S. Lashley—The Neuropsychology of Lashley—most of which described rat and monkey studies directed toward understanding memory, perception, and motor behavior.
Again, neuropsychology was neither used nor defined in the text. To the extent that they did use the term, however, these writers, who specialized in the study of basic brain function in animals, were recognizing the emergence of a subdiscipline of investigators who specialized in human research and would find the animal research relevant to understanding human brain function.
Today, we define neuropsychology as the study of the relation between human brain function and behavior. Although neuropsychology draws information from many disciplines—for example, anatomy, biology, biophysics, ethology, pharmacology, physiology, physiological psychology, and philosophy—its central focus is the development of a science of human behavior based on the function of the human brain.
As such, it is distinct from neurology, which is the diagnosis of nervous system injury by physicians who are specialists in nervous system diseases, from neuroscience, which is the study of the molecular basis of nervous system function by scientists who mainly use nonhuman animals, and from psychology, which is the study of behavior more generally.
Neuropsychology is strongly influenced by two traditional foci of experimental and theoretical investigations into brain function: the brain hypothesis, the idea that the brain is the source of behavior; and the neuron hypothesis, the idea that the unit of brain structure and function is the neuron. This chapter traces the development of these two ideas. We will see that, although the science is new, its major ideas are not.
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