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chapter1 - A Brain on the Ceiling of the Sistine Chapel...

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Unformatted text preview: A Brain on the Ceiling of the Sistine Chapel? Between 1508 and 1512, Michelangelo (1475—1564) painted the Sistine Chapel in the Vatican. One panel of the ceiling, his masterpiece The Creation ofAdam (shown on the right), depicts God reaching out to bestow the gift of life upon humanity, through Adam. But the oddly shaped drapery behind God, and the arrangement of his attendants, has prompted speculation that Michelangelo was conveying a hidden message: God and attendants appear to be part of a human brain (Mesh— berger, 1990). Only a little imagination is required to identify the broad outlines of a brain in Michelangelo’s depiction of God (compare it with the midline section of a human brain in Figure 2.1219). During the Renaissance, when this fresco was created, the all-powerful church forbade depiction of the dissected human body, considering it to be a desecration. But there is no doubt that Michelangelo engaged in extensive dissections of cadavers, gaining the detailed knowledge of human anatomy that informs his sculpture and paintings. It is highly likely that he knew perfectly well What a dissected human brain looks like. So, was Michelangelo making a subtle commentary about the origins of behavior, God’s most magnificent creation, or the secrets of nature? We probably will never know. But we can all agree that our uniquely human qualities—language, reason, emotion, and the rest—are products of the brain. The goal of this book is to give you some idea of how this mysterious organ enables humans to paint a masterpiece, sing an aria, or uncover some of the secrets of that very brain itself. 11 this book we explore the many ways in which the structures and actions of the brain produce mind and behavior. But that is only half of our task. We are also interested in the ways in which behavior in turn modifies the structures and actions of the brain. One of the most important lessons we hope to convey is that interactions between brain and behavior are reciprocal. The brain controls behav- ior and, in turn, behavior alters the brain. We hope to give an interesting account of the main ideas and research in bio— logical psychology, which is of great popular as well as scientific interest. Because there are so many pieces to tie together, we try to introduce a given piece of infor— mation when it makes a difference to the understanding of a subject—especially When it forms part of a story. Most important, we seek to communicate our own interest and excitement about the mysteries of mind and body. What Is Biological Psychology? No treaty or trade union agreement ever defined the bOundaries of biological psy- chology. The first peeple‘ to study the relationships between brain and behavior regarded themselves as philosophers, and their findings contributed to the births of biology and psychology. A merging of those disciplines, biological psychology is the field that relates behavior to bodily processes, especially the workings of the 2 CHAPTER 1 5 known as neuroscience (the root neuro— comes from the Greek word neuron, meaning “nerve” or “cord”), biological psychology is also known as behavioral neuroscience. Whichever name is used, the main goal of this field is to understand the biology underlying behavior and experience. is afield that includes many players who come from quite gists, biologists, physiologists, engineers, neurolor biological psychology Also called brain. Because study of the brain i behavioral neuroscience. The study of the biological bases of psychological processes and behavior. euroscience The study of the nenrous Biological psychdogy n different backgrounds: psycholo system. ' ,'_Behavioral.- medicine 3 Developmental neurobiology - 1.1 How Biological Psychology Relates to Other Fields of Study In this graphical representation of the relationships among . biological psychology and other ‘ ; scientific disciplines, fields to— = ‘ ward the center of the map are closest to biological psychology in their history, outlook, aims, and/or methods. BlOLOGlCAL PSYCHOLOGY; SCOPE AND OUTLOOK 3 gists, psychiatrists, and many others. Thus, there are many career opportunities, in both universities and private industry, for people with interests in this field (Hitt, 2007). Figure 1.1 maps the relations of biological psychology to these many other disciplines. Clearly, the biological psychology umbrella is very wide. Five Viewpoints Explore the Biology of Behavior In our pursuit to understand the biological bases of behavior, we use several dif- ferent perspectives. Because each one yields information that complements the others, the combination of perspectives is especially powerful. The five major per- spectives are 1. Describing behavior 2. Studying the evolution of behavior 3. Observing the development of behavior and its biological characteristics over the life span 4. Studying the biological mechanisms of behavior 5. Studying applications of biological psychology—for example, its applications to dysfunctions of human behavior These perspectives are discussed in the sections that follow, and Table 1.1 shows how each perspective can be applied to three kinds of behavior. Behavior can be described according to different criteria Until we describe what we want to study, we cannot accomplish much. Depending on the goals of our investigation, we may describe behavior in terms of detailed acts or processes, or in terms of results or functions. An analytical description of arm movements might record the successive positions of the limb or the cunt-rac- tion of different muscles. A functional behavioral description, by contrast, would state whether the limb was being used in walking, running, hopping,swimming, or texting. To be useful for scientific study, a description must be precise and reveal the essential features of the behavior, using accurately defined terms and units. Kind of behavior Research , perspective Sexual behavior Learning and memory Language and communication DESCRIPTION _ Structural What are the main patterns of In what main ways does behavior How are the sounds of speech reproductive behavior and sex change as a consequence of patterned? ' differences in behavior? experiencewfor example, conditioning? Functional How do specialized patterns of How do certain behaviors lead to What behavior is involved in making behavior contribute to mating rewards or avoidance of statements or asking questions? and to care of young? punishment? _ EVOLUTION How does mating depend on How do. different species compare How did the human speech hormones in different species? in kinds and speed of learning? apparatus evolve? DEVELOPMENT How do reproductive and How do learning and memory How do children learn to speak? secondary sex characteristics change ove:r the life span? develop over the life span? MECHANISMS What neural circuits and hormones What anatomical and chemical What brain regions are particularly are involved in reproductive . changes in the brain hold involved in language? behavior? memories? _ APPLICATIONS Low doses of testosterone Gene therapy and behavioral Speech therapy, in conjunction with ' restore libido in some postmenopausal women. therapy improve memory in some senile patients. amphetamine treatment, speeds language recovery following stroke. 4 CHAPTER 1 conserved In the context of Evolution, referring to a trait that is passed on from a common ancestor to two or more descendant species. ontogeny The process by which an indi- vidual changes in the course of its lifetime— that is, grows up and grows old. neuron Also called nerve cell. The basic unit of the nervous system. - We compare species to learn how the brain and behavior have evolved Darwin’s theory of evolution through natural selection is central to all modern biology and psychology: From this perspective emerge two rather different em- phases: (1) the continuity of behavior and biological processes among species be— cause of our common ancestry and (2) the species-specific dzfierences in behavior and biology that have evolved as adaptations to different environments. At some points in this book we will concentrate on continuity—that is, features of behavior and its biological mechanisms that are common to many species. At other points, we will look at behaviors displayed by only a few species. , _ Nature is conservative. Once particular features of the body or behavior evolve, they may be maintained for millions of years and may be seen in animals that oth— erwise appear very different. For example, the electrical messages used by. nerve cells (see Chapter 3) are essentially the same in a jellyfish, a cockroach, and a hu— man being. Some of the chemical compounds that transmit messages through the bloodstream (hormones) are also the same in diverse animals (see Chapter 5). Spe- cies share these conserved characteristics because the features first arose in a shared ancestor (Box I .1). But mere similarity, of a feature between species does not guar— antee that the feature came from a common ancestral species. Similar solutions to a problem may have evolved independently in different classes of animals. The body and behavior develop over the life span Ontogeny is the process by which an individual changes in the course of its life— time—that is, grows up and grows old. Observing the way in which a particular behavior changes during ontogeny may give us clues to its functions and mecha— nisms. For example, we know that learning ability in monkeys increases over sev- eral years of development. Therefore, we can speculate that prolonged maturation of brain circuits is required for complex learning tasks. In rodents, the ability to form long—term memories lags somewhat behind the maturation of learning abil- ity. So, young rodents learn well but forget more quickly than older ones, suggest— ing that learning and memory involve different processes. Studying the develop— ment of reproductive capacity and of differences in behavior between the sexes, along with changes in body structures and processes, enables us to throw light on body mechanisms underlying sex behaviors. Biological mechanisms underlie all behavior The history of a species tells us the evolutionary determinants of its behavior; the history of an individual tells us the developmental determinants. To learn about the mechanisms of an individual’s behavior, we study how his or her present body works. To understand the underlying mechanisms of behavior, we must regard the organism (with all due respect) as a “machine,” made up of billions of nerve cells, or neurons (the Greek word for "nerve" or "cord”). We must ask, How is this thing constructed to be able to do all that? _ Our major aim in biological psychology is to examine body mechanisms that make particular behaviors possible. In the case of learning and memory, for exam- ple, we would like to know the sequence of electrical and biochemical processes that occur when we learn something and retrieve it from memory. What parts ,of the nervous system are involved in that process? In the case of reproductive behavior, we would like to know how the body grows to produce the capacity for sexual behavior. We also want to understand the neuronal and hormonal pro- cesses that underlie reproductive behavior. ,Research can be applied to human problems Like other sciences, biological psychology is also dedicated to improving the human condition. As Albert Einstein once said, concern for humanity and its fate must al~ BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 5 .. Each person has some characteristics shared by... all animals. .. its-DNA, ' ...5.t .essneug firifpsmsfisn: . all vertebrates. .. all other primates (_e.g., hav- ing a hand with an ‘opposég; able thumb and a relatively 3 large, complex brain). I Whether knowledge gained about a process in anotherspecies applies to humans depends on whether we are like that species in regard to that - process. The fundamental research on the _ 5 mechanisms of inheritance in the bac-‘ _ _ ‘ terium Escherichia coli prov'ed‘So widely: '. ‘ f applicable that some molecular biologists E proclai_m_ed,;”What is_true of- E. coli is true-'5 _._ of the elephant.” To a remarkable-extent ' that statement is true, but there" are also - i ' . . someiimportant differences in the genetic‘ mechanisms of E. coliand mammals; ' I I With respectto each biological prop-'_ . erty, researchers must determinehow _ '. animals are identical and howtheyare __ . different. When we seek animal models '--=for studying human behavior or biological ' _ . _ ‘ _ .. ._- _ . .. - . . processes, we must ask-the following ques— .. How'do'similarities and differences ajr'nong'f' tio_n:_Does the proposed animal'modei ' - ' '. people-andanimals fit into biological " - "really-hm somethings _in common with '. psychology? Each person is in some ways I "the process at work in humans? We will ' like _all other people, in some ways like ' seemany cases in which it does) _ ' some other people, and in some ways like " Even within the same species, how- no other person. As the figure shows, We ever, individuals differ from one another: _' can extendthis observation to the much - ;_ cat from cat, bluejay from blue jay, and broader range ofanimai life. insome j 3 ‘ _ person from person. Biological psychology _ ways each person is like all other animals seeks to understand individual differences ' ' (e.g.,needing to ingest complex organic :‘asrwell as similarities. Therefore, the way ‘ nutrients), insome Ways like all other -- in which each person is able to process in- vertebrates (e.g., having a spinal column), __for_mat_ion and store-the memories of these -_ in some ways like all other mammals (e.g.,- "experiences is another part of Our story. nursing our young), and in some ways like ' all mammals... all primates. .. _ . no other person. ways form the chief interest of all scientific endeavors “in order that the creations of our minds shall be a blessing and not a curse.” Numerous human diseases involve malfunctioning of the brain. Many of these are already being alleviated as a result of research in the neurosciences, and the prospects for continuing advances are good. 6 CHAPTER 1 somatic intervention An approach to finding relations between body variables and behavioral variables that involves manipulat- ing body structure or function and looking for resultant changes in behavior. independent variable The factor that is manipulated by an experimenter. dependent variable The factor that an experimenter measures to monitor a change in response to changes in an independent variable. behavioral intervention An approach to finding relations between body variables and behavioral variables that involves intervening in the behavior of an organism and looking for resultant changes in body structure or function. 1.2 Three Main Approaches to Study- ing the Neuroscience of Behavior (a) In somatic intervention, investigators change the body structure or chemistry of an animal in some way and observe and measure any resulting behavioral effects. (b) Conversely, in behavioral intervention, researchers change an animal's behavior or its environment and try to ascertain whether the change results in physiological or anatomical changes. (c) Measurements of both kinds of variables allowresearchers to arrive at correlations between somatic - changes and behavioral changes. (d) Each approach enriches and informs the others. (a) Manipulating the body may affect behavior Attempts to apply knowledge also benefit basic research. For example, the study of memory disorders in humans has pushed investigators to extend our knowledge of the brain regions involved in different kinds of memory (see Chapter 17). Three Approaches Relate Brain‘ and Behavior Biological psychologists use three approaches to understand the relationship be- tween brain and behavior: somatic intervention, behavioral intervention, and cor- relation. In the most common approach, somatic intervention (Figure 'l.2u), we alter a structure or function of the brain or body to see how this alteration changes behavior. Here, somatic intervention is the independent variabI/e, and the behavior- al effect is the dependent variable; that is, the resulting behavior depends on how the brain has been altered. For example, in response to mild electrical stimulation of one part of her brain, not only did one patient laugh, but she found-Whatever she happened to be looking at amusing (Fried et al., 1998). I ‘ In later chapters we describe many kinds of somatic mtervention with both humans and other animals, as in the following examples: 0 A hormone is administered to some'animals but not to others; various behaviors of the two groups are later compared. ' ' A part of the brain is stimulated electrically, and behavioral effects are observed. ' A connection between two parts of the nervous system is cut, and changes in behavior are measured. The approach opposite to somatic intervention is psychological or behavioral intervention (Figure 1.21)). In this approach, the scientist intervenes in the behav- ior of an organism and looks for resulting changes in body structure or function. Here, behavior is the independent variable, and change in the body is the depen— dent variable. Among the examples that we will consider in later chapters are the following: ' 0 Putting two adults of opposite sex together may lead to increased secretion of certain hormones. (c) Body and behavioral measures covary Behaviors affected Behavioral variables ((1) Biological psychology seeks to understand all these relationships Somatic intervention I’x/ fl Behavioral intervention BIOLOGICAL PSYCHOLOGY: SCOPE AND OUTLOOK 0 Exposing a person or animal to a visual stimulus provokes changes in electrical activity and blood flow in parts of the brain. 0 Training of animals in a maze is accompanied by electrical, biochemical, and anatomical changes in parts of their brains. The third approach to brain—behavior relations, correlation (Figure 1.2:), con- sists of finding the extent to which a given body measure varies with a given be- havioral measure. Later we will examine the following questions, among others: 0 Are people with large brains more intelligent than people with smaller brains? 0 Are individual differences in sexual behavior correlated with levels of certain hormones in the individuals? 0 ls the severity of schizophrenia correlated with the magnitude of changes in brain structure? Such correlations shOuld not be taken as proof of causal relationship. For one thing, even if a causal relation exists, the correlation does not reveal its direction— that is, which variable is independent and which is dependent. For another, two factors might be correlated only because a third, unknown factor affects the two factors measured. What a correlation does indicate is that the two variables are linked in some way—directly or indirectly. Such a correlation often stimulates in— vestigators to formulate hypotheses and to test them by somatic or behavioral intervention. Combining these three approaches yields the circle diagram of Figure 1.211. This diagram incorporates the basic approaches to studying relationships between bodily processes and behavior. It also emphasizes the theme that the relations be— tween brain and body are reciprocal: each affects the other in an ongoing cycle of bodily and behavioral interactions. We will see examples of this reciprocal rela— tionship throughOut the book. Neuroplasticity: Behavior Can Change the Brain The idea that there is a reciprocal relationship between brain and behavior has embedded within it a concept that is, for most people, startling. When we say that behavior and experience affect the brain, we mean that they, literally, physically alter the brain. The brain of a child growing up in a French-speaking household assembles itself into a configuration different from that of the...
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