PSY 280 - Breedlove Chapters 1-4 PDF

Psychiatry & Behavioral Sciences, Stanford Medical School Care System, Palo Alto, CA and Dr. Ahmad Salehi, Dept. of Introduction...

Psychiatry & Behavioral Sciences, Stanford Medical School Care System, Palo Alto, CA and Dr. Ahmad Salehi, Dept. of Introduction Courtesy of Dr. Sarah Moghadam, VA Palo Alto Health Scope and Outlook Machine or Human? In the near future depicted in the HBO series Westworld, people visit a theme park set in the Old West, with steam locomotives, saloons, and brothels, populated with an- droids, called “hosts,” to entertain humans. The mechanical hosts provide their guests with anything, from casual banter to gunfights, harmless flirting to kinky sex, the only 1 restriction being that the robots are never to harm the humans. The android hosts are so lifelike in appearance and behavior that visitors may have a hard time distinguishing whether someone is a fellow guest or a robot. To make the androids’ simulation of hu- mans complete, they are given backstories, false memories of a life before their appear- ance for each new batch of guests. Importantly, none of the androids know that they are mechanical beings rather than humans. It’s probably not much of a spoiler to say that several plot lines in the series hinge on androids slowly discovering their true nature, moving from shock and shame that they are mere machines, to openly rebelling from the notion that they are to be used, and abused, as mere playthings for the humans. We aren’t told too much about how the android “brains” in Westworld work, be- cause, of course, such technology remains far outside our grasp, so the writers, reduced to mere speculation, remain rather vague. But apparently the knowledge and personality for any particular android lies in a “control unit,” a golf-ball-size device that can be extracted from the head of one host and implanted into the head of another, interchangeable body. Presumably, if we had enough knowledge and surgical skill, we could remove your brain from your head and connect it up to the head of some other body. Would you still be you? Even if we put your brain into a body of the opposite sex? Come to think of it, are you entirely sure there is a brain in your head, and not one of those control units? Our aim in this book is to help you learn what is known so far about how brains work, and about how much more we have yet to learn. We will 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 and experi- ence modify the structures and actions of the brain. One of the most important lessons we want to convey is that interactions between brain and behavior are reciprocal. The brain controls behavior and, in turn, behavior and experience alter the brain. We hope to give an interesting account of the main ideas and research in be- havioral neuroscience, which is of great popular as well as scientific interest. Most important, we try to communicate our own interest and excitement about the mys- teries of mind and body. Go to Brain Explorer bn9e.com/be1  1.1 The Brain Is Full of Surprises Learning Objectives After reading this section, you should be able to: 1.1.1  Name the main type of cells found in the brain, and name the connections between them. 1.1.2  List the names of some of the many fields of study related to behavioral neuroscience. 1.1.3  Describe five different perspectives taken in understanding the biology of behavior. I used to think that the brain was the most wonderful organ in my body. Then I realized who was telling me this. —Emo Philips (American comedian) Of course we should always consider the source when evaluating an idea, but even so, the brain indeed seems like a pretty wonderful organ. For one thing, brains pro- duced the entire extent of human knowledge, everything we understand about the universe, however limited that may be. Brains also produced every written descrip- tion of that hard-won knowledge (including this book you hold in your hands), as well as every work of visual art, from doodles to the sweeping frescos on the ceiling of the Sistine Chapel. Most of us have a hard time grasping the idea of a billion of anything, but your head contains an estimated 86 billion nerve cells, or neurons (from the Greek word for “nerve” or “cord”) (Herculano-Houzel, 2012). Each neuron contacts many other cells at points called synapses, so there are trillions of those between your ears. A specialized extension of neurons, called an axon, is microscopically slender, yet it may neuron Also called nerve cell. The basic be several feet long. We’ll learn that axons produce electrical impulses that travel unit of the nervous system. hundreds of miles per hour. FIGURE 1.1 offers a list of just a few of the things we will © Dwayne Godwin, 2011 1.1 Your Brain by the Numbers The cerebral cortex is the outermost portion of the brain. 2 C HA PT E R 1 learn about the human brain in the course of this book. All this hardware isn’t just for neuroscience The study of the show—it allows you to take in all the information in that figure in less than a minute. nervous system. behavioral neuroscience Also called What is behavioral neuroscience? biological psychology. The study of the No treaty or trade union agreement defines the boundaries of behavioral neuroscience. neural bases of behavior and mental The first people to study the relationships between brain and behavior regarded them- processes. selves as philosophers, and their findings contributed to the births of biology and psy- chology. Those disciplines merged in the twentieth century to form biological psychology, the field that relates behavior to bodily processes. With the modern explosion of neuro- science, the study of the brain, this research has evolved to the point that behavioral neuroscience offers a more accurate description. Whichever name is used, the main goal of this field is to understand the neuroscience underlying behavior and experience. Behavioral neuroscience is a field that includes many players who come from quite different backgrounds: psychologists, biologists, physiologists, engineers, neurolo- 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 1.2 maps the relations of behavioral neuroscience to these many oth- er disciplines. Clearly, the behavioral neuroscience umbrella opens very wide. Cognitive science Computer Anthropology science Cognitive psychology Evolutionary Sociobiology Artificial Psychiatry biology intelligence Cognitive Behavioral neuroscience Behavioral ecology/ethology Social Neural medicine neuroscience modeling Comparative/ Health Paleontology evolutionary psychology Neurology Paleoneuro- psychology Clinical Cognitive neuro- anatomy Comparative neuro- psychology neuroanatomy BEHAVIORAL psychology Neural NEUROSCIENCE Neuro- Neuro- imaging physiology Electro- anatomy physiology Anatomy Developmental Psycho- Physiology psychobiology pharmacology Behavior Psychoneuro- Developmental genetics immunology Pharmacology neurobiology Behavioral endocrinology Developmental Genetics/ Neuro- Biochemistry biology epigenetics immunology Neuro- endocrinology Molecular Immunology biology Endocrinology 1.2 What’s in a Name? In this graphical representation of the relationships among behavioral neuroscience and other scientific disciplines, fields toward the center of the map are closest to behavioral neuroscience in their history, outlook, aims, and/or methods. In trodu ctio n 3  Five viewpoints explore the biology of behavior In our effort to understand the neuroscience 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. We will discuss five major perspectives: 1. Describing behavior 2. Observing the development of behavior and its biological characteristics over the life-span 3. Studying the biological mechanisms of behavior 4. Studying applications of behavioral neuroscience—for example, its application to dysfunctions of human behavior 5. Studying the evolution of behavior These perspectives are discussed in the sections that follow, and TABLE 1.1 illustrates 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 our goals, 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 contraction of different muscles. A functional behavioral description, by contrast, would state whether the limb was being used in walking or running, texting or sexting. 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. TABLE 1.1 Five Research Perspectives Applied to Three Kinds of Behavior Language and Research perspective Sexual behavior Learning and memory communication DESCRIPTION Structural What are the main patterns In what main ways does How are the sounds of speech of reproductive behavior behavior change as a patterned? and sex differences in consequence of experience— behavior? for example, conditioning? Functional How do specialized patterns How do certain behaviors lead What behavior is involved in of behavior contribute to rewards or avoidance of making statements or asking to mating and to care of punishment? questions? young? ONTOGENY How do reproductive How do learning and memory What changes in the brain (development) and secondary sex change as we grow older? when a child learns to characteristics develop speak? over the life-span? MECHANISMS What neural circuits and What anatomical and chemical What brain regions are hormones are involved in changes in the brain hold particularly involved in reproductive behavior? memories? language? APPLICATIONS Low doses of testosterone Gene therapy and behavioral Speech therapy, in conjunction restore libido in some therapy improve memory in with amphetamine treatment, postmenopausal women. some senile patients. speeds language recovery following stroke. EVOLUTION How does mating depend How do different species How did the human speech on hormones in different compare in kinds and speed apparatus evolve? species? of learning? 4 C HA PT E R 1 The body and behavior develop over the life-span conserved In the context of evolution, referring to a trait that is passed on from Ontogeny is the process by which an individual changes in the course of its life- a common ancestor to two or more time—that is, grows up and grows old. Observing the way in which a particular descendant species. behavior changes during ontogeny may give us clues to its functions and mech- ontogeny The process by which an anisms. For example, we know that learning ability in monkeys increases over individual changes in the course of its the first years of life. Therefore, we can speculate that prolonged maturation of lifetime—that is, grows up and grows old. brain circuits is required for complex learning tasks. In rodents, the ability to form long-term memories lags somewhat behind the maturation of learning ability. So, young rodents learn well but forget more quickly than older ones, suggesting that learning and memory involve different processes. Studying the development of reproductive capacity and of differences in behavior between the sexes, along with changes in body structures and processes, throws light on body mechanisms un- derlying sexual behaviors. Biological mechanisms underlie all behavior 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 neurons. We must ask, How is this thing constructed to be able to do all that? These are sometimes described as proximate questions—questions about the physical inter- actions that control a particular behavior. How cells in your eye respond differently to light of different wavelengths is a proximate question. On the other hand, why color vision, once it arose, benefited our ancestors is an evolutionary question. Our major aim in behavioral neuroscience is to examine body mechanisms that make particular behaviors possible. In the case of learning and memory, for example, we would like to know the sequence of electrical and biochemical processes that oc- cur 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 also want to understand the neuronal and hormonal processes that underlie mating behaviors. Research can be translated to address human problems Like other sciences, behavioral neuroscience is also dedicated to improving the human condition. Numerous human diseases involve malfunctioning of the brain. Many of these are already being alleviated as a result of research in the neuro- sciences, and the prospects for continuing advances are good. 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). We compare species to learn how the brain and behavior have evolved 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 otherwise 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 human being. Some of the chemical compounds that transmit messages through the bloodstream (hormones) are also the same in diverse animals (see Chapter 5). Species share these conserved characteristics because the features first arose in a shared ancestor (BOX 1.1 on the next page). But mere similarity of a feature between species does not guarantee that the feature came from a common ancestral species. Similar solu- tions to a problem may have evolved independently in different classes of animals. Charles Darwin’s theory of evolution through natural selection is central to all modern biology. From this perspective emerge two rather different emphases: (1) the continuity of behavior and biological processes among species that reflects shared ancestry and (2) the species-specific differences in behavior and biology that have evolved as adaptations to different environments. In tro ductio n 5  B OX 1.1 We Are All Alike, and We Are All Different Each person has some characteristics shared by… all animals… All animals use DNA to store genetic information. all vertebrates… All vertebrates have a backbone and spinal cord. all mammals… Whether knowledge gained about All mammals a process in another species applies suckle their to humans depends on whether we young. are like that species in regard to that process. The fundamental research on all the mechanisms of inheritance in the primates… bacterium Escherichia coli proved so All primates have a hand with an opposable widely applicable that some molecular thumb and a relatively biologists proclaimed, “What is true large, complex brain. of E. coli is true of the elephant.” To a remarkable extent, that statement is all true, but there are also some important humans differences in the genetic mechanisms (people)… All humans use symbolic of E. coli and mammals. language to communicate With respect to each biological with each other. property, researchers must deter- mine how animals are identical and How do similarities and differ- how they are different. When we seek some people… ences among people and animals animal models for studying human fit into behavioral neuroscience? behavior or biological processes, we Some people like Each person is in some ways like must ask the following question: Does to eat beets (no one knows why). all other people, in some ways like the proposed animal model really some other people, and in some have some things in common with the ways like no other person. As the process at work in humans (Seok et figure shows, we can extend this al., 2013)? We will see many cases in No two people, even observation to the much broader which it does. identical twins, are alike no other in each and every way, as range of animal life. Each person is Even within the same species, person. individual experiences in some ways like all other animals however, individuals differ from one leave their unique stamp (e.g., needing to ingest complex another: cat from cat, blue jay from on every brain. organic nutrients), in some ways like blue jay, and person from person. all other vertebrates (e.g., having a Behavioral neuroscience seeks to spinal column), in some ways like understand individual differences all other mammals (e.g., nursing our as well as similarities. Therefore, the young), and in some ways like all way in which each person is able to other primates (e.g., having a hand process information and store the with an opposable thumb and a memories of these experiences is relatively large, complex brain). another part of our story. Behavioral Neuroscience 9E Breedlove Sinauer Associates Breedlove9e_Box01.01.ai Date 07-15-19 6 C HA P T E R 1  1.2 Three Approaches Relate Brain and Behavior somatic intervention An approach to finding relations between body variables Learning Objectives and behavioral variables that involves manipulating body structure or function and After reading this section, you should be able to: looking for resultant changes in behavior. 1.2.1  Differentiate between the independent and dependent variables in scientific experiments. independent variable The factor that is manipulated by an experimenter. 1.2.2  Name the type of research in which a part of the brain is manipulated to observe effects on behavior, and offer examples. dependent variable The factor that 1.2.3  Name the type of research in which behavior or experience is manipulated an experimenter measures to monitor a to observe effects on the brain, and offer examples. change in response to manipulation of an 1.2.4  Describe correlational research about the brain and behavior, and independent variable. offer examples. 1.2.5  Explain why the brain must be capable of changing its structure, and name the term to describe that changeability. Behavioral neuroscientists 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 1.3A), we alter a structure or function of the brain or body to see how this alteration changes behavior. Here, somatic intervention is the independent variable, and the behav- ioral 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 stimula- 1.3 Three Main Approaches to tion of one part of her brain, not only did one patient laugh, but she found whatever Studying the Neuroscience of Behavior she happened to be looking at amusing (Fried et al., 1998). (A) In somatic intervention, investigators In later chapters we describe many kinds of somatic intervention with both hu- change the body structure or chemistry of mans and other animals, as in the following examples: an animal in some way and observe and A hormone is administered to some animals but not to others; various behaviors measure any resulting behavioral effects. (B) Conversely, in behavioral intervention, of the two groups are later compared. researchers change an animal’s behavior A part of the brain is stimulated electrically, or by use of light to stimulate only a or its environment and try to ascertain particular class of neurons, and behavioral effects are observed. whether the change results in physiological or anatomical changes. (C) Measurements A connection between two parts of the nervous system is cut, and changes in of both kinds of variables allow researchers behavior are measured. 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 (B) Experience affects the body (including the brain) Somatic interventions Behaviors affected Somatic effects Behavioral interventions Strength of mating Changes in hormone Put male in presence Administer a hormone behavior levels of female Stimulate brain region Movement toward Changes in electrical Present a visual electrically goal object activity of brain stimulus Cut connections between Recognition of Anatomical changes parts of nervous system stimulus Give training in nerve cells (C) Body and behavioral measures covary (D) Behavioral neuroscience seeks to understand all Somatic variables Behavioral variables these relationships Brain size Correlations Learning scores Somatic intervention Strength of mating Hormone levels Correlations behavior Somatic variables Correlations Behavioral variables Enlarged cerebral Schizophrenic Behavioral Correlations intervention ventricles symptoms Introductio n 7 behavioral intervention An approach The approach opposite to somatic intervention is psychological or behavioral to finding relations between body variables intervention (FIGURE 1.3B). In this approach, the scientist intervenes in the be- and behavioral variables that involves havior or experience of an organism and looks for resulting changes in body struc- intervening in the behavior of an organism ture or function. Here, behavior is the independent variable, and change in the and looking for resultant changes in body structure or function. body is the dependent variable. Among the examples that we will consider in later chapters are the following: correlation The covariation of two measures. Putting two adults of opposite sex together may lead to increased secretion of certain hormones. neuroplasticity Also called neural plasticity. The ability of the nervous Exposing a person or animal to a visual stimulus provokes changes in electrical system to change in response to activity and blood flow in parts of the brain. experience or the environment. 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 1.3C), con- sists of finding the extent to which a given body measure varies with a given behav- ioral measure. Later we will examine the following questions, among others: Are people with large brains more intelligent than people with smaller brains (a topic we’ll take up later in this chapter)? Are individual differences in sexual behavior correlated with levels of certain hormones in the individuals? Is 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. If you and your study partner get similar scores on an exam, that’s not because your performance caused her to get the score she did, or vice versa. What a correlation does suggest is that the two variables are linked in some way—directly or indirectly. Such a correlation often stimulates investigators to formulate hypotheses and to test them by somatic or behavioral intervention. Only by moving on to such intervention ap- proaches can we establish whether one variable is causing changes in the other. Combining these three approaches yields the circle diagram of FIGURE 1.3D, incor- porating the basic approaches to studying relationships between bodily processes and behavior. It also emphasizes the theme that the relations between brain and behavior are reciprocal: each affects the other in an ongoing cycle of bodily and behavioral in- teractions. We will see examples of this reciprocal relationship throughout the book. Neuroplasticity: behavior can change the brain The idea that there is a reciprocal relationship between brain and behavior has embed- ded 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 Go to Media Clip 1.1 Neuroplasticity brain of a child growing up in a French-speaking household assembles itself into a con- bn9e.com/mc1.1 figuration different from that of the brain of a child who hears only English. That’s why the first child, as an adult, understands French effortlessly while the second does not. In this case we cannot tell you what the structural differences are exactly, but we do know one part of the brain that is being altered by these different experiences (see Chapter 19). Numerous examples, almost all in animal subjects, show that experience can affect the number or size of neurons, or the number or size of connections between neurons. This ability of the brain, both in development and in adulthood, to be changed by the environment and by experience is called neuroplasticity (or neural plasticity, or simply plasticity). Today when we hear the word plastic, we think of the class of materials found in so many modern products. But originally, plastic meant “flexible, malleable” (from the Greek plassein, “to mold or form”), and the modern materials were named plastics be- cause they can be molded into nearly any shape. In 1890, William James (1842–1910) 8 C HA P T E R 1 described plasticity as the possession of a structure weak enough to Only in this brain region yield to an influence but strong enough not to yield all at once. 12 was growth stunted by the In the ensuing years, research has shown that the brain is even lack of opportunity to play. more plastic, more yielding, than James suspected. For example, parts 10 Volume (mm3 × 10–1) of neurons known as dendritic spines (see Chapter 2) appear to be in Social 8 constant motion, changing shape in the course of seconds. We will Isolated see many examples in which experience alters the structure and/or 6 function of the brain: In Chapter 5, you’ll read that hearing a baby cry 4 causes the mother’s brain to secrete a hormone. In Chapter 7, we’ll see that visual experience in kittens directs the formation of connections 2 in the brain. In Chapter 12, we’ll discuss how a mother rat’s grooming of her pups affects the survival of spinal cord neurons. And Chapter 0 Posterodorsal Anterodorsal Anteroventral Posteroventral 17 talks about how a sea slug learning a task changes the connections Quadrants of the medial amygdala between two particular neurons. 1.4 The Role of Play in Brain Behavioral neuroscience and social psychology are related Development A brain region involved in The plasticity of the human brain has a remarkable consequence: other individuals processing odors (the posterodorsal por- can affect the physical structure of your brain! Indeed, the whole point of coming to a tion of the medial amygdala) was smaller in male rats housed individually than in lecture hall is to have the instructor use words and figures to alter your brain so that males housed together and allowed to you can retrieve that information in the future (in other words, teach you something). play. Other nearby regions were identical Many of these alterations in your brain last only until you take an exam, but every once in the two groups. (After B. M. Cooke et in a while the instructor may tell you something that you’ll remember for the rest of al., 2000. Behav Brain Res 117: 107–113.) your life. Most aspects of our social behavior are learned—from the language we speak to the clothes we wear and the kinds of food we eat—so the mechanisms of learning and memory (see Chapter 17) are important for understanding social behavior. For an example from an animal model, consider the fact that rats spend a lot of time investigating the smells around them, including those coming from other rats. Cooke et al. (2000) took young male rats, just weaned from their Behavioral mother, and Neuroscience 9E raised them in two different ways: either alone in separate cages, orBreedlove with other males in group cages so they could engage in play (including a lot ofSinauer Associates sniffing of each other’s butts). Examination of these animals as adults found only one brain Breedlove9e_1.04.ai Date 07-15-19 difference between the groups: a region of the brain known to process odors was smaller in the isolated males than in the males raised with playmates (FIGURE 1.4). Was it the lack of play (N. S. Gordon et al., 2003), the lack of odors to investi- gate, or the stress of isolation that made the region smaller? Whatever the mecha- nism, social experience affects this brain structure. In Chapter 17 we’ll see more examples of social experience altering the brain. Here’s an example of how social influences can affect human brain function. When people were asked to put a hand into moderately hot water (47°C), part of the brain became active, presumably because of the discomfort involved (Rain- ville et al., 1997). But people who were led to believe the water would be very hot had a more activated brain than did those led to believe the discomfort would be minimal From P. Rainville, 1998. Presented at INABIS '98, 5th Internet (FIGURE 1.5), even though the water was University, Canada, Dec 7–16th. Available at http://www. the same temperature for everyone. The so- mcmaster.ca/inabis98/woody/rainville0419/index.html World Congress on Biomedical Sciences at McMaster cially induced psychological expectation af- fected the magnitude of the brain response, 1.5 Pictures of Pain People told to expect only mild discomfort from putting a hand into 47°C water (left) showed less activation in a par- ticular brain region (the anterior cingulate cortex) than did people expecting more discomfort (right) from water of the very same temperature. Areas of high activation are indicated by orange, red, and white. In trodu ctio n 9  even though the physical stimulus was exactly the same. (By the way, the people with the more activated brains also reported feeling more pain.) In most cases, biological and social factors continually interact and affect each other in an ongoing series of events as behavior unfolds. For example, the level of the hormone testosterone in circulation can affect dominance behavior and aggression (see Chapter 15). The dominance may be exhibited in a great variety of social settings, ranging from playing chess to physical aggression. In humans and other primates, the level of testosterone correlates positively with the degree of dominance and with the amount of aggression exhibited. Winning a contest, whether a game of chess or a boxing match, raises the level of testosterone; losing a contest lowers the level. Thus, at any moment the level of testosterone is determined, in part, by recent dominant- submissive social experience, and the level of testosterone determines, in part, the de- gree of dominance and aggression in the future. Of course, social and cultural factors also help determine the frequency of aggression; cross-cultural differences in rates of aggression exist that cannot be correlated with hormone levels, and ways of express- ing aggression and dominance are influenced by sociocultural factors. Perhaps nothing distinguishes neuroscience from the other sciences more clearly than this fascination with neuroplasticity and the role of experience. Neuroscientists have a pervasive interest in how experience physically alters the brain and therefore affects future behavior. We will touch on this theme in every chapter of this book. 1.3 Behavioral Neuroscientists Use Several Levels of Analysis Learning Objectives After reading this section, you should be able to: 1.3.1  Name and describe the scientific approach of explaining mechanisms at simpler and simpler levels. 1.3.2  Give a survey of important ongoing questions about the relationship between the brain and behavior. 1.3.3 Offer estimates of the extent of neurological and psychiatric disorders. 1.3.4  Explain the importance of research with animals for neuroscience, and discuss the ethics of such research. Scientific explanations of systems or structures or functions usually involve break- ing them down into smaller parts, as a way of understanding them. This approach is known as reductionism. In principle, it is possible to reduce each explanatory series down to the molecular or atomic level, though for practical reasons this extent of reductionism is rare. For example, most chemists deal with large, complex molecules and the laws that govern them; seldom do they seek explanations in terms of sub- atomic quarks and bosons. Understanding behavior often requires several levels of biological analysis. The units of each level of analysis are simpler in structure and organization than those of the level above. The levels of analysis range from social interactions to the brain, continuing to successively less complex units until we arrive at single nerve cells and their even sim- pler, molecular constituents. Naturally, in all fields different problems are carried to different levels of analy- sis, and fruitful work is often being done simultaneously by different workers at several levels (FIGURE 1.6). Thus, in their research on visual perception, cognitive neuroscientists advance analytical descriptions of behavior. They try to determine reductionism The scientific strategy of how the eyes move while looking at a visual pattern, or how the contrast among breaking a system down into increasingly smaller parts in order to understand it. parts of the pattern determines its visibility. Meanwhile, other behavioral neurosci- entists study the differences in visual abilities among species and try to determine levels of analysis The scope of the adaptive significance of these differences. For example, how is the presence experimental approaches. A scientist may try to understand behavior by monitoring (or absence) of color vision related to the life of a species? At the same time, other molecules, nerve cells, brain regions, or investigators trace out brain structures and networks involved in different kinds of social environments, or some combination visual discrimination. Still other scientists try to ascertain the electrical and chemi- of these levels of analysis. cal events that occur in the brain during vision. 10 C HAP T E R 1  Social level: Neural systems level: Individuals behaving Eyes and visual brain regions in social interaction Organ level: Brain, spinal cord, Brain region level: peripheral nerves, Visual cortex and eyes Circuit level: Local neural circuit Cellular level: Single neuron Molecular level Synaptic level Membrane receptors 1.6 Levels of Analysis in Behavioral Neuroscience The scope of behavioral neuro- science ranges from the level of the individual interacting with others, to the level of the mol- ecule. Depending on the question at hand, investigators use different techniques to focus on these many levels, but always with an eye toward how their findings apply to behavior. We will encounter many diverse brain and behavior topics Here areNeuroscience Behavioral some examples 9E of research topics considered in this book: Breedlove How does the brain grow, maintain, and repair itself over the life-span (see Sinauer Associates Chapter 7), and how are these capacities related to the growth and development Breedlove9e_1.06.ai of the mind and behaviorDatefrom07-15-19 the womb to the tomb? How does the nervous system capture, process, and represent information about the environment? For example, sometimes brain damage causes a person to lose the ability to identify other people’s faces (see Chapter 18); what does that tell us about how the brain recognizes faces? How does sexual orientation develop? Some brain regions are different in straight versus gay men (see Figure 12.26); what, if anything, do those differences tell us about the development of human sexual orientation? Some people suffer damage to the brain and afterward seem alarmingly unafraid in dangerous situations and unable to judge the fearfulness of other people; what parts of the brain are damaged to cause such changes (see Figure 15.16)? How does the brain manage to change during learning (see Chapter 17), and how are memories retrieved? What brain sites and activities underlie feelings and emotional expression? Are particular parts of the brain active in romantic love, for example (FIGURE 1.7A)? Why are different brain regions active during different language tasks (FIGURE 1.7B)? Introdu ctio n 11  (A) (B) From A. Bartels and S. Zeki, 2000. Hearing words Seeing words Neuroreport 11: 3829–3834 Courtesy of Marcus Raichle Reading words Generating words 1.7 “Tell Me Where Is Fancy Bred, Or in the Heart Or in the Head?” (A) The parts of the brain highlighted here become especially active when a person thinks about his or her romantic partner. (B) Different brain regions are activated when people perform four different language tasks. The techniques used to generate such images are described in Chapter 2. The relationship between the brain and behavior is, on the one hand, very mys- terious because it is difficult to understand how a physical device, the brain, could be responsible for our subjective experiences of fear, love, and awe. Yet despite this mystery, we all use our brains every day. Perhaps it is the “everyday miracle” Behavioral Neuroscience 9E aspect of the topic that has generated so much folk wisdom about the brain. Think Breedlove Sinauer Associates of it as “neuromythology.” Sometimes these popular ideas about the brain are in line with our current Breedlove9e_1.07.ai Date 07-15-19 knowledge, but in many cases we know they are false. For example, the notion that we normally use only 10% of our brain is commonplace—a survey of teachers found that nearly half of them agreed with this notion (Howard-Jones, 2014)—but it is patent nonsense. Brain scans make it clear that the entire brain is activated by even fairly mundane tasks. Indeed, although the areas of activation shown in Fig- ure 1.7 appear rather small and discrete, we will show in Box 2.3 that experimenters must work very hard to create images that separate activation related to a particular task from the background of widespread, ongoing brain activity. We offer a list of other commonly held beliefs about the brain and behavior on the website in A STEP FURTHER 1.1 : NEUROMYTHOLOGY: FACTS OR FABLES? Throughout the book we offer such opportunities for you to explore a given topic in more detail on the website, bn9e.com. Behavioral neuroscience contributes to our understanding of human disorders One of the great promises of neuroscience is that it can help us understand brain disorders and devise treatment strategies. Like any other complex mechanism, the brain is subject to a variety of malfunctions and breakdowns. People afflicted by disorders of the brain are not an exotic few—a European survey estimated that at least 38% of the population would suffer from a mental disorder at some point in a typical year (Wittchen et al., 2011). At least one person in five around the world currently has neurological and/or psychiatric disorders that vary in severity from mild challenges to complete disability. FIGURE 1.8A shows the estimated numbers of U.S. residents afflicted by some of the main neurological disorders. FIGURE 12 C HA P T E R 1 (A) Prevelence of neurological disorders (B) Prevelance of psychiatric disorders 1.8 The Toll of Brain Disorders Estimated numbers of people in the United States with Other neurological disorders (A) and number of dementias people worldwide with psychiatric disorders 2,200,000 Depression (B). (Part A after C. L. Gooch et al., 2017. Ann Alzheimer’s 268,000,000 5,300,000 Neurol 81: 479–484; B after H. Ritchie and M. Epilepsy 2,800,000 Alcohol use Roser, 2019. "Mental Health". Published online 109,000,000 at OurWorldInData.org. Retrieved from: https:// ourworldindata.org/mental-health. Underlying Drug use Anxiety data available from http://ghdx.healthdata.org/ Stroke 73,000,000 disorders gbd-results-tool.) 6,800,000 289,000,000 Traumatic brain injury 1,700,000 Spinal cord MS Parkinson’s Eating Schizophrenia Bipolar injury 600,000 disease disorders 19,500,000 disorder 340,000 1,000,000 16,000,000 47,000,000 1.8B gives estimates of the numbers of adults worldwide with certain psychiatric disorders. The percentage of U.S. adults suffering from mental illness may be in- creasing (Twenge, 2015; Twenge et al., 2010). The toll of these disorders is enormous, in terms of both individual suffering and social costs (Demyttenaere et al., 2004). The National Advisory Mental Health Council has estimated that direct and indirect costs of behavioral and brain dis- orders amount to $400 billion a year in the United States alone. For example, the cost for treatment of dementia (severely disordered thinking) exceeds the costs of treating cancer and heart disease combined. The World Health Organization (2004) estimates that over 15% of all disease burden, in terms of lost productivity, is due to mental disorders. The high cost in suffering and expense has compelled researchers to try to understand the mechanisms involved in these disorders and to try to alleviate or even prevent them. In this quest, the distinction between clinical and laboratory approaches begins 1.9 Identical Twins but Nonidentical Brains and Behavior In these images to fade away. For example, when clinicians encounter a pair of twins, one of whom of the brains of identical twins, the fluid- has schizophrenia while the other seems healthy, the discovery of structural dif- filled cerebral ventricles are prominent ferences in their brains (FIGURE 1.9) immediately raises questions for laboratory as dark “butterfly” shapes. The brain of scientists: Did the structural differences arise before the symptoms of schizophre- the twin with schizophrenia (A) has the nia, or the other way around? Were the brain differences present at birth, or did enlarged cerebral ventricles that some they arise during puberty? Does medication that reduces symptoms affect brain researchers believe are characteristic of structure? When genes associated with schizophrenia in people are introduced this disorder. The other twin does not have schizophrenia; his brain (B) clearly into mice, will that change the mouse brains (see Figure 16.7)? This has smaller ventricles. last question is just one instance of when working with animals is essential, an issue we address next. (A) Twin with (B) Unaffected twin schizophrenia Animal research makes vital contributions Because we will draw on animal research throughout this book, we want to comment on some of the ethical issues of experimentation on animals. Human beings’ involvement and concern with other species predates recorded history. Early humans had to study animal behavior MRIs courtesy of E. Fuller Torrey and physiology in order to escape some species and hunt others. To study biological bases of behavior inevitably requires research on ani- and Daniel Weinberger mals of other species as well as on human beings. Psychology students usually underestimate the contributions of animal research because the most widely used introductory psychology textbooks often pres- ent major findings from animal research as if they were obtained with human participants (Domjan and Purdy, 1995). Behavioral Neuroscience 9e Fig. 01.08 Dragonfly Media Group Intro ductio n 13 07/25/19  Because of the importance of carefully reg- ulated animal research for both human and animal health and well-being, the National Research Council (NRC Committee on Ani- mals as Monitors of Environmental Hazards, 1991) undertook a study on the many uses of animals in research. The study noted that 93% of the mammals used in research are laboratory-reared rodents. It also reported that © Santa Cruz Sentinel/ZUMAPRESS.com most Americans believe that animal research should continue. Of course, researchers have an obligation to minimize the discomfort of their animal subjects, and ironically enough, animal research has provided us with the drugs and techniques to make most research painless for the animal subjects (Sunstein and Nussbaum, 2004). Nevertheless, a very active minority of peo- 1.10 Car Firebombed by Animal ple believe that research with animals, even if Rights Activists The extremists target- it does lead to lasting benefits, is unethical. For ed the cars and homes of two scientists example, in his 1975 book Animal Liberation, Peter Singer asserts that research with who work with animals at the University animals can be justified only if it actually produces benefits. The trick, of course, of California in Santa Cruz in 2008. The is how to predict which experiment will lead to a breakthrough. Thus Singer re- next year, the car of a researcher at fuses to say that animal experimentation is never justified (Neale, 2006). In the UCLA was torched. meantime, animal rights groups have vandalized labs, burned down buildings, and exploded bombs in laboratories (Conn and Parker, 2008). In 2008, animal rights extremists set off firebombs at the homes of two scientists in Santa Cruz, California. One scientist’s family, including two young children, had to flee their home through a second-story window (FIGURE 1.10) (Paddock and La Ganga, 2008). These personal attacks on individuals appear to be intended to intimidate and frighten scientists (D. Grimm, 2014), and they have already hounded at least one researcher out of the field (Nature Neuroscience, 2015). Perhaps in a future where robots can be made that look and act like humans, methods will be available to clearly see all the processes at work in a living, work- ing human brain. In the meantime, there’s no substitute for research with animal subjects. Every chapter in this book is teeming with information that was gathered from humane experiments with animals. 1.4 The History of Research on the Brain and Behavior Begins in Antiquity Learning Objectives After reading this section, you should be able to: 1.4.1  race the historical point at which the brain was recognized as the control T unit for behavior. 1.4.2  iscuss the importance of the Renaissance in better understanding human D anatomy. 1.4.3  xplain Descartes’s contribution to early neuroscience and his now- E discredited ideas of dualism. 1.4.4  race the history of phrenology and the relationship to modern thinking T about brain and behavior. 1.4.5  iscuss the difficult question of consciousness and the explosion of D neuroscience research. Only recently have scientists recognized the central role of the brain in controlling behavior. When Egyptian pharaoh Tutankhamen was mummified (about 1300 bce), five important organs were preserved in his tomb: liver, lungs, stomach, intestines, and heart. All these organs were considered necessary to ensure the pharaoh’s con- tinued existence in the afterlife. The brain, however, was picked out through the 14 C HAP T E R 1 nostrils (FIGURE 1.11) and thrown away. Although the Egyptian version of the after- life entailed considerable struggle, the brain was not considered an asset. Neither the Hebrew Bible (written from the twelfth to the second century bce) nor the New Testament ever mentions the brain. However, the Bible mentions the heart hundreds of times and makes several references each to the liver, the stom- ach, and the bowels as the seats of passion, courage, and pity, respectively. “Teach us … that we may gain a heart of wisdom” (Psalms 90:12). The heart is also where Aristotle (about 350 bce), the most prominent scientist of ancient Greece, located mental capacities. We still reflect this ancient notion when we call people kindhearted, openhearted, fainthearted, hardhearted, or heartless and when we speak of learning by heart. Aristotle considered the brain to be only a cooling unit to lower the temperature of the hot blood from the heart. Also about 350 bce, the Greek physician Herophilus (the “Father of Anatomy”) advanced our knowledge of the nervous system by dissecting bodies of both peo- ple and animals. He traced nerves from muscles and skin into the spinal cord and noted that each region of the body is connected to separate nerves. A second-century Greco-Roman physician, Galen, treated the injuries of gladi- ators. His reports of behavioral changes caused by injuries to the heads of gladia- tors drew attention to the brain as the controller of behavior. Galen advanced the Photograph by Neil Watson idea that animal spirits—a mysterious fluid—passed along nerves to all regions of the body. But Galen’s ideas about the anatomy of the human brain were very inac- curate because dissecting humans was illegal in Rome at that time. Renaissance scientists began to understand brain anatomy The eminent Renaissance painter and scientist Leonardo da Vinci (1452–1519) stud- ied the workings of the human body and laid the foundations of anatomical drawing. He especially pioneered in providing views from different angles and cross-sectional 1.11 Brain Removal Kit Ancient Egyp- tians had little regard for the brain. During representations. His artistic renditions of the body included portraits of the nerves in mummification, they would use tools like the arm and the fluid-filled ventricles in the brain (FIGURE 1.12). these to reach through the nostrils to pick Renaissance anatomists emphasized the shape and appearance of the external out brain pieces and throw them away. surfaces of the brain because these were the parts that were easiest to see when the skull was removed. It was immediately apparent to anyone who looked that the brain (A) Early drawing (B) Later drawing based on observation Her Majesty Queen Elizabeth II, copyright reserved Reproduced with gracious permission of 1.12 Leonardo da Vinci’s Changing View of the (B) Later he made a drawing based on direct observation: Brain (A) In an early representation, Leonardo simply after making a cast of the ventricles of an ox brain by copied old schematic drawings that represented the fluid- pouring melted wax into the brain and letting it set, he cut filled cerebral ventricles as a linear series of chambers. away the tissue to reveal the true shape of the ventricles. In troductio n 15  1.13 An Early Account of Reflexes In this depiction of an explanation by Des- cartes, when a person’s toe touches fire, the heat causes nervous activity to flow up the nerve to the brain (blue arrows). From there the nervous activity is “reflected” back down to the leg muscles (red arrows), which contract, pulling the foot away from the fire; the idea of activity being reflected back is what gave rise to the word reflex. In Descartes’s time, the difference between sensory and motor nerves had not yet been discovered, nor was it known that nerve fibers normally conduct in only one direction. Nevertheless, Descartes promoted thinking about bodily processes in scientific terms, and this focus led to steadily more accurate knowledge and concepts. has an extraordinarily complex shape. To Renaissance artists like Michelangelo (1475–1564), this marvelous structure was God’s greatest gift to humankind. So, in Michelangelo’s painting on the ceiling of the Sistine Chapel, God seems to ride the form of the human brain when bestowing life to Adam (Meshberger, 1990), while in another scene God’s throat resembles the base of the brain (Suk and Tamargo, 2010). In 1633, René Descartes (1596–1650) wrote an influential book (De Homine [On Man]) in which he tried to explain how the behavior of animals, and to some extent the behavior of humans, could be like the workings of a machine. Descartes proposed the concept of spinal reflexes and a neural pathway for them (FIGURE 1.13). Attempting to relate the mind to the body, Descartes sug- gested that the two come into contact in the pineal gland, located within the brain. He suggested the pineal gland for this role because (1) whereas most brain struc- tures are double, located symmetrically in the two hemispheres, the pineal gland is single, like consciousness, and (2) he believed, erroneously, that the pineal gland exists only in humans and not in animals. As Descartes was preparing to publish his book, he learned that the Catholic Church had forced Galileo to renounce his teaching that Earth revolves around the sun, threatening to execute him if he did not recant. Fearful that his own specula- tions about mind and body could also incur the wrath of the church, Descartes withheld his book from publication. It did not appear in print until 1662, after his death. Descartes believed that if people were nothing more than intricate machines, they could have about as much free will as a pocket watch, with no opportunity to make the moral choices that were so important to the church. He asserted that Behavioral Neuroscience 9E humans, at least, had a nonmaterial soul as well as a material body. This notion Breedlove of dualism spread widely and left other philosophers with the task of determin- Sinauer Associates ing how a nonmaterial soul could exert influence over a material body and brain. Breedlove9e_1.13.ai Mainstream neuroscientists reject dualism and insist that all the workings of the Date 07-15-19 mind can also, in theory, be understood as purely physical processes in the material world, specifically in the brain. The concept of localization of function arose in the nineteenth century By the end of the 1600s, the English physician Thomas Willis (1621–1675), with his detailed descriptions of the structure of the human brain and his systematic study of brain disorders, convinced educated people in the Western world that the brain is the organ that coordinates and controls behavior (Zimmer, 2004). A popular notion of the nineteenth century, called phrenology, elaborated on this idea by asserting that the cerebral cortex consisted of separate functional areas and that each area was responsible for a behavioral faculty such as love of family, perception of color, or curi- osity. Investigators assigned functions to brain regions anecdotally, by observing the dualism Here, the notion promoted by René Descartes that the mind is subject behavior of individuals and inferring, from the shape of the skull, which underlying only to spiritual interactions while the body regions of the brain were more or less developed (FIGURE 1.14A). is subject only to material interactions. Opponents rejected the entire concept of localization of brain function, insisting phrenology The outmoded belief that that the brain, like the mind, functions as a whole. Today we know that the whole bumps on the skull reflect enlargements brain is indeed active when we are doing almost any task. When we are performing of brain regions responsible for certain particular tasks, however (as we saw earlier in this chapter), certain brain regions behavioral faculties. become even more activated. Different tasks activate different brain regions. Modern 16 C HAP T E R 1 (A) (B) Voluntary eye Face Motor execution Visual spatial movements Hand attention Foot Anticipation Motor Analytic preparation Face Somatosensory cortex and figural Hand reasoning Foot Visual spatial Spatial working attention memory Analytic reasoning Mathematical approximations Mathematical approximations Anticipation of pain Visual spatial attention Object working Motion perception © The Print Collector/Alamy Stock Photo memory Speed perception Exact Primary visual mathematical cortex calculations Color perception Olfaction Pleasant Face recognition touch Olfaction Pain Auditory cortex Speech Anticipation Semantic priming Spoken language production of pain of visual words comprehension 1.14 Old and New Phrenology (A) In the early nineteenth century, certain “faculties,” such as skill at mathematics or a tendency toward aggression, were believed to be directly associated with particular brain regions. Phrenologists used diagrams like this one to measure bumps on the skull, which they took as an indication of how fully developed each brain region was in an individual, and hence how fully that person should display particular qualities. (B) Today, technology enables us to roughly gauge how active different parts of the brain are when a person is performing various tasks (see Chapter 2). But virtually the entire brain is active during any task, so the localization of function that such studies provide is really a measure of where peak activity occurs, rather than a suggestion of a single region involved in a particular task. (B after M. J. Nichols and W. T. Newsome, 1999. Nature 402: C35–C38.) Behavioral Neuroscience 9E Breedlove brain maps Sinauer of these places Associates where peaks of activation occur (FIGURE 1.14B) bear a passing resemblance to their phrenological predecessors, differing only in the spe- Breedlove9e_1.14.ai Date cific locations of functions. But 07-15-19 unlike the phrenologists, we confirm these modern maps by other methods, such as examining what happens after brain damage. Even as far back as the 1860s, the French surgeon Paul Broca (1824–1880) argued that language ability was not a property of the entire brain but rather was localized in a restricted brain region. Broca presented a postmortem analysis of a patient who had been unable to talk for several years. The only portion of the patient’s brain that appeared damaged was a small region within the frontal portions of the brain on the left side—a region now known as Broca’s area (labeled “Speech production” in Figure 1.14B). The study of additional patients further convinced Broca that language expression is mediated by this specific brain region rather than reflecting activities of the entire brain. In 1890, William James’s book The Principles of Psychology signaled the begin- nings of a modern approach to behavioral neuroscience. The strength of the ideas described in this book is evident from the continuing frequent citation of the work. In James’s work, psychological ideas such as consciousness and other aspects of human experience came to be seen as properties of the nervous system. A true behavioral neuroscience began to emerge from this approach. These nineteenth-century observations form the background for a continuing theme of research in behavioral neuroscience—notably, the search for distinguishing differences among brain regions on the basis of their structure, and the effort to re- late different kinds of behavior to different brain regions (M. Kemp, 2001). An addi- tional theme emerging from these studies is the relation of brain size to ability across species (see Figure 6.9), and even across various people (BOX 1.2 on the next page). Intro ductio n 17  B OX 1.2 Bigger Better? The Case of the Brain and Intelligence Does a bigger brain indicate greater The development and standardiza- est thickening of the outer layer of the intelligence? Brain size does s