ORIGINS OF PHYSIOLOGICAL PSYCHOLOGY
Describe the behavior of people with split brains, and explain what this phenomenon contributes to our understanding of self-awareness.
Describe the goals of scientific research.
Describe the biological roots of physiological psychology.
Describe the role of natural selection in the evolution of behavioral traits.
Discuss the value of research with animals and ethical issues concerning their care.
Describe career opportunities in neuroscience.
- The last frontier in the world – and perhaps the greatest one – lies within us. The human nervous system makes possible all that we can do, all we can know, and all that we can experience. Its complexity is immense, and the task of studying it and understanding it dwarfs all previous explorations our species has undertaken.
- A mind, a soul, or a spirit. What is the nature of the human mind? Within our bodies the nervous system plays a central role, receiving information from the sensory organs and controlling the movements of the muscles. But what is the mind, and what role does it play? Does it control the nervous system? Is it a part of the nervous system? Is it physical and tangible, like the rest of the body, or is it a spirit that will always remain hidden?
- Most of us believe that the mind is a phenomenon produced by the workings of the nervous system. We believe that once we understand the workings of the human body – in particular, the workings of the nervous system – we will be able to explain how we perceive, how we think, how we remember, and how we act.
Understanding Human Consciousness: a Physiological Approach
- How can physiological psychologists study human consciousness? Consciousness: the fact that we are aware of – and can tell others about – our thoughts, perceptions, memories, and feelings.
- Brain damage and drugs can profoundly affect consciousness. Because consciousness can be altered by changes in the structure or chemistry of the brain, we may hypothesize that consciousness is a physiological function, just like behavior. Consciousness and the ability to communicate seem to go hand in hand. That is, our ability to send and receive messages with other people enables us to send and receive our own messages – in other words, to think and to be aware of our own existence.
- Disconnecting parts of the brain that are involved with perception from parts involved with verbal behavior also disconnect them from consciousness.
- These results suggest that the parts of the brain involved in verbal behavior may be the ones responsible for consciousness.
- The corpus callosum is a large bundle of nerve fibers that connect corresponding parts of one side of the brain with those of the other.
- The largest part of the brain consists of two symmetrical parts, called the cerebral hemispheres, which receive sensory information from the opposite sides of the body. They also control movements of the opposite sides. The corpus callosum enables the two hemispheres to share information so that each side knows what the other side is perceiving and doing. After the split-brain operation is performed, the two hemispheres are disconnected and operate independently. Their sensory mechanisms, memories, and motor systems can no longer exchange information. The effects of these disconnections are not obvious to the casual observer, for the simple reason that only one hemisphere – in most people, the left – controls speech. The right hemisphere of an epileptic person with a split brain appears to be able to understand verbal instructions reasonably well, but it is totally incapable of producing speech.
- One of the first things that these patients say they notice after the operation is that their left hand seems to have a "mind of its own." This conflict occurs because the right hemisphere, which controls the left hand, cannot read and therefore finds the book boring.
- One exception of the crossed representation of sensory information is the olfactory system. That is, when a person sniffs a flower through the left nostril, only the left brain receives a sensation of the odor. Thus, if the right nostril of a patient with a split brain is closed, leaving only the left nostril open, the patient will be able to tell us what the odors are. However, if the odor enters the right nostril, the patient will say that he or she smells something. But, in fact, the right brain has perceived the odor and can identify it. To show this is so, we ask the patient to smell an odor with the right nostril and then reach for some objects that are hidden from view by a partition. If asked to use the left hand, controlled by the hemisphere that detected the smell, the patient will select the object that corresponds to the odor – a plastic flower for a floral odor, a toy fish for a fishy odor, a model tree for the odor of pine, and so forth. But if asked to use the right hand, the patient fails the test because the right hand is connected to the left hemisphere, which did not smell the odor.
- The effects of cutting the corpus callosum reinforce the conclusion that we become conscious of something only if information about it is able to reach the parts of the brain responsible for the verbal communication, which are located in the left hemisphere. If the information does not reach these parts of the brain, then that information does not reach the consciousness associated with these mechanisms. We still know very little about the physiology of consciousness, but studies of people with brain damage are
- beginning to provide us with some useful insights. This issue is discussed in later chapters.
The Nature of Physiological Psychology
The modern history of physiological psychology has been written by psychologists who have combined the experimental methods of psychology with those of physiology and have applied them to the issues that concern all psychologists. Thus, we have studied perceptual processes, control of movement, sleep and waking, reproductive behaviors, ingestive behaviors, emotional behaviors, learning, and language. In recent years we have begun to study the physiology of human pathological conditions, such as addiction and mental disorders.
The Goals of Research
- The goal of all scientists is to explain the phenomena they study. Scientific explanation takes tow forms: generalization and reduction. Most psychologists deal with generalization. They explain particular instances of behavior as examples of general laws, which they deduce from their experiments.
- Most physiologists deal with reduction. They explain complex phenomena in terms of simpler ones. For example, they may explain the movement of a muscle in terms of the changes in the membranes of muscle cells, the entry of particular chemicals, and the interactions among protein molecules within these cells.
- The task of the physiological psychologists is to explain behavior in physiological terms. But physiological psychologists cannot simply be reductionists. We must understand "psychologically" why a particular behavior occurs before we can understand what physiological events made it occur.
- Mice will build nests under two conditions: when the air temperature is low and when the animal is pregnant. The same behavior occurs for different reasons. If fact, nest-building behavior is controlled by two different physiological mechanisms. Nest building can be studied as a behavior related to the process of temperature regulation, or it can be studied in the context of parental behavior.
- Sometimes, physiological mechanisms can tell us something about psychological processes. Damage to a specific part of the brain can cause very specific impairments in a person’s language abilities. The nature of these impairments suggests how these abilities are organized. When the damage involves a brain region that is important in analyzing speech sounds, it also produces deficits in spelling. This finding suggests that the ability to
recognize a spoken word and the ability to spell it call on related brain mechanisms. Damage to another region of the brain can produce extreme difficulty in reading unfamiliar words by sounding them out, but it does not impair the person’s ability to read words with which he or she is already familiar. This findings suggest that reading comprehension can take two routes: one related to speech sounds and another that is primarily a matter of visual recognition of whole words.
- In practice, the research efforts of physiological psychologists involve both forms of explanation – generalization and reduction. Ideas for experiments are stimulated by the investigator’s knowledge both of psychological generalizations about behavior and of physiological mechanisms. A good physiological psychologist must therefore be both a good psychologist and a good physiologist.
Biological Roots of Physiological Psychology
- Rene Descartes’ speculations about the roles of the mind and brain in the control of behavior provide a good starting point in the history of physiological psychology. To Descartes, animals were mechanical devices; their behavior was controlled by environmental stimuli. His view of the human body was much the same: it was a machine. Reactions like this did not require participation of the mind; they occurred automatically. He called them reflexes.
- Descartes was a duelist; he believed that each person possesses a mind – a unique human attribute that is not subject to the laws of the universe. He was the first to suggest that a link exists between the human mind and its purely physical housing, the brain.
- He noted that the brain contains hollow chambers (the ventricles) that are filled with fluid, and he hypothesized that this fluid is under pressure. In his theory, when the mind decides to perform an action, it tilts the pineal body in a particular direction like a little joystick, causing fluid to flow from the brain into the appropriate set of nerves. This flow of fluid causes the same muscles to inflate and move.
- In science, a model is a relatively simple system that works on known principles and is able to do at least some of the things a more complex system an do.
- Galvin found that electrical stimulation of a frog’s nerve caused contraction of the muscle to which it was attached. Contraction occurred even when the nerve and muscle were detached from the rest of the body, so the ability of the muscle to contract and the ability of the nerve to send a message to the muscle were characteristics of these tissues themselves. Thus, the brain did not inflate muscles by directing pressurized fluid though the nerve.
- Johannes Muller was a forceful advocate of the application of experimental techniques of physiology. In his doctrine of specific nerve energies, Muller observed that although all nerves carry the same basic message – an
electrical impulse – we perceive the messages of different nerves in different ways.
- The answer is that the messages occur in different channels. The portion of the brain that receives messages from the optic nerves interprets the activity as visual stimulation, even if the nerves are actually stimulated mechanically. Because different parts of the brain receive messages from different nerves, the brain must be functionally divided: Some parts perform some functions, while other parts perform others.
- Flourens removed various parts of animals’ brains and observed their behavior. This method is called experimental abolition.
- Paul Broca applied the principle of experimental ablation to the human brain. He observed the behavior of people whose brains had been damaged by strokes. In 1861 he performed an autopsy on the brain of a man who had had a stroke that resulted in the loss of the ability to speak.
- In 1870, German physiologists Gustav Fritsch and Eduard Hitzig used electrical stimulation as a tool for understanding the physiology of the brain. They applied weak electrical current to the exposed surface of a dog’s brain and observed the effects of the stimulation. They found that stimulation of different portions of a specific region of the brain caused contraction of specific muscles on the opposite side of the body. We now refer to this region as the primary motor cortex, and we know that nerve cells there communicate directly with those that cause muscular contractions.
- Hermann von Helmholtz devised a mathematical formulation of the law of conservation of energy, invented the ophthalmoscope (used to examine the retina of the eye), devised an important and influential theory of color vision and color blindness, and studied audition, music, and many physiological processes.
- Helmholtz was also the first scientist to attempt to measure the speed of conduction through nerves. But Helmholtz found that neural conduction was much slower – only about 90 feet per second.
Functionalism: Nature Selection and Evolution
- Darwin formulated the principles of evolution and natural selection, which revolutionized biology. He noted that across succeeding generations, individual members of a species spontaneously undergo structural changes. If these changes produce favorable effects that permit the individual to reproduce more successfully, some of the individual’s offspring will inherit the favorable characteristics and will themselves produce more offspring.
- Darwin’s theory emphasized that all of an organism’s characteristics – its structure, its coloration, its behavior – have functional significance. For example, the strong talons and sharp beaks that eagles possess permit the birds to catch and eat prey.
- Darwin’s theory gave rise to functionalism, a belief that characteristics of living organisms perform useful functions. So, to understand the physiological
basis of various behaviors, we must first understand what these behaviors accomplish. We must therefore understand something about the natural history of the species being studied so that, the behaviors can be seen in context.
- To understand that workings of a living organism, we should know what its functions are.
- The cornerstone of this theory is the principle of natural selection. Briefly, here is how the process works: Every sexually reproducing multicellular organism consists of a large number of cells, each of which contains chromosomes. Chromosomes are large, complex molecules that contain the recipes for producing the proteins that cells need to grow and to perform their function. In essence, the chromosomes contain the blueprints for the construction (that is, the embryological development) of a particular member of a particular species. If the plans are altered, a different organism is produced.
- The plans do get altered; mutations occur from time to time. Mutations are accidental changes in the chromosomes of sperms or eggs that join together and develop into new organisms.
- Most mutations are deleterious; the offspring either fails to survive or survives with some sort of deficit. However, a small percentage of mutations are beneficial and confer a selective advantage. Many different kinds of traits can confer a selective advantage: resistance to a particular disease, the ability to digest new kinds of food, more effective weapons for defense or for procurement of prey, and even a more attractive appearance to members of the opposite sex (after all, one must reproduce to pass on one’s chromosomes).
- Variety is a definite advantage for a species. Different environments provide optimal habitats for different kinds of organisms.
- When I ask my students what they think they ultimate function of the brain is, they often say "thinking," or "logical reasoning," or "perceiving," or "remembering things." Certainly, the nervous system performs these functions, but they support the primary one: control of movement.
- And thinking can often take place without causing any overt behavior. However, the ability to think evolved because it has a useful function: It permits us to perform complex behaviors that accomplish useful goals.
- An understanding of the principle of natural selection plays some role in the thinking of every person who undertakes research in physiological psychology. Some researchers explicitly consider the genetic mechanisms of various behaviors and the physiological processes upon which these behaviors depend. Others are concerned with comparative aspects of behavior and its physiological basis; they compare the nervous systems of animals from a variety of species to make hypotheses about the evolution of brain structure and the behavioral capacities that correspond to this evolutionary development.
Ethical Issues in Research with Animals
Most of the research described in this book involves experimentation on living animals. Any time we use another species of animals for our won purposes, we should be sure that what we are doing is both humane and worthwhile.
Our species is beset by medical, mental, and behavioral problems, many of which can be solved only through biological research. Let us consider some of the major neurological disorders. Strokes, caused by bleeding or occlusion of a blood vessel within the brain, often leave people partly paralyzed, unable to read, write, or converse with their friends and family. Basic research on the means by which nerve cells communicate with each other has led to important discoveries about the causes of the death of brain cells. This research was not directed toward a specific practical goal; the potential benefits actually came as a surprise to the investigators.
Research with laboratory animals has produced important discoveries about the possible causes of potential treatments of produced important discoveries about the possible causes or potential treatments of neurological and mental disorders, including Parkinson’s disease, schizophrenia, manic-depressive illness, anxiety disorders, obsessive-compulsive disorders, anorexia nervosa, obesity, and drug addictions.
Some people have suggested that instead of using laboratory animals in our research, we could use tissue cultures or computers. Unfortunately, neither tissue cultures nor computers are substitutes for living organisms. We have no way to study behavioral problems such as addictions in tissue cultures, nor can we program a computer to simulate the workings of an animal’s nervous system. (If we could, that would mean we already had all the answers.)
The easiest way to justify research with animals is to point to actual and potential benefits to human health.
Careers in Neuroscience
- Physiological psychologists study behavioral phenomena that can be observed in nonhuman animals. They attempt to understand the physiology of behavior: the role of the nervous system, interacting with the rest of the body (especially the endocrine system, which secretes hormones), in controlling behavior. They study such topics as sensory processes, sleep, emotional behavior, ingestive behavior, aggressive behavior, sexual behavior, parental behavior, and learning and memory. They also study animal models of disorders that afflict humans, such as anxiety, depression, obsessions and compulsions, phobias, psychosomatic illnesses, and schizophrenia.
- Although physiological psychology is the original name for this field, several other terms are now in general use, such as biological psychology, biopsychology, psychobiology, and behavioral neuroscience.
Physiological psychology belongs to the larger field of neuroscience. Neuroscientists concern themselves with all aspects of the nervous system: its anatomy, chemistry, physiology, development, and functioning. The research of neuroscientists ranges from the study of molecular genetics to the study of social behavior.
Most professional physiological psychologists are employed by colleges and universities, where they are engaged in teaching and research. Others are employed by institutions devoted to research – for example, laboratories owned and operated by national governments or by private philanthropic organizations. A few work in industry, usually for pharmaceutical companies that are interested in assessing the effects of drugs on behavior. To become a professor or independent researcher, one must receive a doctorate. Nowadays, most physiological psychologists spend two years in temporary postdoctoral position, working in the laboratory of a senior scientist to gain more research experience.
Two other fields often overlap with that of physiological psychology: neurology and experimental neuropsychology. Neurologists are physicians involved in the diagnosis and treatment of diseases of the nervous system.
Experimental neuropsychologists – scientists with a Ph. D. in psychology and specialized training in the principles and procedures of neurology.
Strategies for Learning
- Learning about the physiology of behavior involves much more that memorizing facts. The antidote to obsolescence is knowledge of the process by which facts are obtained. In recognition of these realities about learning, knowledge, and the scientific method, this book presents not just a collection of facts, but a description of the procedures, experiments, and logical reasoning that scientists have used in their attempt to understand the physiology of behavior.
- Now let me offer some practical advice about studying. If possible, the first reading of the assignments should be as uninterrupted as u can make it; that is, read the chapter without worrying much about remembering details. Be active, not passive. Force yourself to write down whole words and phrases. Rephrasing the information in your own words starts the learning process right then.
- If you make yourself remember the information long enough to write it down, you have a good chance of remembering it later.
Understanding Human Consciousness: A physiological approach
- Physiological psychologists believe that the mind is a function performed by the brain.
- Study of human brain functions has helped us gain some insight into the nature of human consciousness, which appears to be related to the language functions of the brain. This chapter described one example, the effects of the split-brain operation.
The Nature of Physiological Psychology
- Scientists attempt to explain natural phenomena by means of generalization and reduction. Because physiological psychologists use the methods of psychology and physiology, they employ both types of explanations.
- Descartes developed the first model to explain how the brain controls movement, based on the animated statues in the Royal Gardens. Subsequently, investigators tested their ideas with scientific experiments.
- Darwin’s theory of evolution, with its emphasis on function, helps physiological psychologists discover the relations between brain mechanisms, behaviors, and an organism’s adaptation to its environment.
Ethical Issues in Research with Animals
- Scientific research with animals has taught us most of what we know about the functions of the body, including that of the nervous system. This knowledge is essential in developing ways to prevent and treat neurological and mental disorders.
Careers in Neuroscience
- Physiological psychologists study the physiology of behavior by performing research with animals. They use the research methods and findings of other neuroscientists in pursuit of their particular interests.