Introduction

None exceeds in its fascination the working of the human brain. Here, in a bare two-handsfull of living tissue, we find an ordered complexity sufficient to embody and preserve the record of a lifetime of the richest human experience. We find a regulator and coordinator of the hundreds of separate muscle systems of the human body that is capable of all delicacy and precision shown by the concert pianist and the surgeon. Most mysterious of all, we find in this small sample of the material universe, and so of the brain itself (MacKay, 1967, p.43).

The human brain is complexly organized tissue composed of living cells. It occupies a volume of about 1,350 cubic centimeters and contains something like 100 billion neurons or nerve cells. Although 100 billion is an almost unimaginably large number, the estimated number of connections between nerve cells is very much larger: There are from 10 trillion to 100 trillion points of cellular contact or synapses within the human nervous system. Clearly, understanding the human brain presents formidable problems.

• The fascination that the human brain holds is not simply that it is large or complicated or that it is intricately and elegantly organized. Its mystery lies in the fact that it controls our behavior, feelings, and thought. In a very real sense, our brains contain the secrets of our selves. Within this complex organ, the ultimate explanation of both mental life and behavior must be sought. Psychoneural identity hypothesis-- is that mental and brain processes are one and the same. Thus the mental events that each of us experiences and each of us believes to be very real are processes of a physical functioning brain. Without a brain, in this view, there can be no mind.

• Metaphysics is the philosopher’s term for the study of the ultimate nature of reality. Various theories have been put forward over the centuries, but two general views predominate. The first is realism, which proposes that the only basic reality is the physical universe. In contrast, idealism argues that the physical world exists only when it enters the thinking of some observer. Thus, for an idealist, the world is only in the minds of human beings.

• Epistemology is the philosopher’s term for the study of the grounds of knowledge. Epistemology asks what is the best approach or strategy for answering metaphysical questions. Empiricism asserts that the key to learning about reality is to rely upon the senses. In contrast, rationalism holds that knowledge can best be gained by logical deduction and mathematical reasoning.

• How is it that a physical brain can be related to a seemingly nonphysical mind? A great many theories as to the relation between the brain and the mind have been proposed.
• Dualisms are theories in which mind and brain are treated as separate and distinct entities. Many different types of dualisms have been proposed over the centuries. Plato’s writings provide an ancient example of dualistic philosophy; classical theology presents another, more familiar example. Dualistic theories argue that, although mind and brain may interact in some way, neither is reducible to the other. In these theories, mind and brain are fundamentally different from each other.
• Pluralisms are theories in which more than two separate and distinct realities are proposed. One recent example of a pluralistic resolution of the mind-brain problem is the Three World theory proposed by John Eccles, a Nobel Prize-winning neurophysiologist, and Karl Popper, a distinguished modern philosopher. They propose that in addition to the subjective world of the mind and the physical world of the brain, there is a third world of objective scientific knowledge.
• Monisms, in contrast, assert that mind and brain are really the same thing. The psychoneural identity hypothesis is a modern example of a monistic philosophy, proposing that psychological processes can ultimately be explained in terms of underlying neural events. It seems that most brain scientists accept this monistic view as both a philosophical basis for their scientific work and a personal view of the world.

• In attempting to understand behavior, brain science is reductionistic. Reductionism is the attempt to explain a phenomenon in terms of the simpler, underlying mechanisms that produce it. To a brain scientist and reductionist, no attempt to understand the biological basis of behavior is satisfactory unless the neural determinants of that behavior can be specified.

A biological explanation of behavior requires that the observations made in a psychological laboratory be related to those obtained by the biological sciences. Sherrington argued that the brain must be understood at three different levels: at the cellular level, at the level of cellular communication, and at the integrative level, expressing the ways in which groups cells govern behavior. Regarding cellular and communicative studies, Sherrington wrote.

Thus, science is both a creative and an empirical enterprise. Curiosity is the driving force behind the scientific enterprise. It is natural for humans to wonder about those things are most human: perception, thought, feeling, and action. Imagination is the key to scientific investigation. Imagination is needed in thinking about new questions, problems, and information and in formulating old ideas in new ways.

• Objectivity is the attempt to approach the experimental questions with an open mind. Although preconceptions and hopes may cloud people’s thinking, it is of primary importance to try to minimize such objective influences.
• Observation. One key to the scientific method is observation: the careful and accurate description of the object of study.
• Experimentation. The experimental method couples observation with the direct manipulation of the object of study and, in so doing, gives the scientific method immense power.
• Paper Controls. Selection of proper experimental controls is vitally important in framing a good experiment, because these controls restrict and clarify the interpretation of experimental results. The selection of useful controls is a matter of careful thinking and good judgment. The choice always depends upon the particulars of a given experiment.
• Statistical Evaluation. In all experiments, only a limited number of individuals are studied, and only a limited number of observations are obtained. Yet the purpose of any experiment is to learn something about people (or animals) in general. This is done be inferring conclusions about the larger category from the behavior of its members that were actually tested. The sample of individuals to be tested must be drawn from the general population in an unbiased manner.
• Independent Verification of Results. Replication of research findings provides a powerful error-correcting mechanism in all of the sciences.
• The Evolution of Science. Ideas often begin as hunches or vague notions. Similarly, experimental methods and designs also evolve. Scientific theories become more powerful and clearer.

Our current understanding of the human brain would not be possible without the tools of modern neurobiology. Golgi, held that the brain was a reticulum, a densely interconnected system of continuous tubes through which unknown substances might flow. Cajal, believed that the brain was composed of individual and separate cells that could communicate with each other. The resolution of this most basic question was provided by the development of a new scientific tool, a silver stain devised by Golgi, which permitted Ramon y Cajal to selectively stain individual neurons within the brain. In this way, we convincingly demonstrated the cellular nature of the brain and established what is now known as the Neuron Doctrine. For their individual contributions, Golgi and Ramon y Cajal shared the Nobel Prize in 1996.

Only a few decades ago, the various brain sciences were viewed as separate research enterprises. Information concerning the physical structure of the nervous system was provided by neuroanatomy. facts concerning the functioning of nerve cells were provided by neurophysiology. Neurochemistry studied the chemical basis of brain activity. Physiological psychology (now called behavioral neuroscience or biological psychology) concerned itself with the biological basis of behavior. It is multidisciplinary nature of contemporary neuroscience that gives the field its vibrant strength.

Ethical guidelines have been established for research involving both human beings and other animal species. Every university has a research review board---composed of a broad range of individuals--- that must approve every experiment in which any living being is placed at any degree of risk, either physical or mental. A typical human subjects or animal protection committee will usually include members from departments not involved with human or animal research, representatives from the schools of law and medicine whenever possible, and interested nonuniversity members, often clerics. This broad representation of divergent perspectives is encouraged to achieve fairness. Once engaged in an experiment, the subjects must be protected from physical and psychological harm. If harm does occur, it is experimenter’s responsibility to provide an appropriate remedy. Finally, data obtained from the human subjects remain confidential. Ethical issues also arise in the experimental studies of nonhuman species, which form the very heart of neuroscience research.

• Research in the neurosciences contributes to the quality of life be expanding knowledge about living organisms. This improvement in the quality of life stems in part from progress toward ameliorating human disease and disability, in part from advances in animal welfare and veterinary medicine, and in part from the steady increase in knowledge of the abilities and potentialities of human and animal life. Continued progress in many areas of biomedical research requires the use of living animals in order to investigate complex systems and functions because, in such cases, no adequate alternatives exist. Progress in both basic and clinical research in such areas cannot continue without the use of living animals as experimented subjects. The use of living animals in properly designed scientific research is therefore both ethical and appropriate. Nevertheless, our concern for the humane treatment of animals dictates that we weigh carefully the benefits to human knowledge and welfare whenever animal research is undertaken (Society for Neuroscience, 1993). All animal research in neuroscience is governed by one overriding principle: that experimental animals must not be subjected to avoidable distress or discomfort.

• Research involving living nonhuman animals has attracted the attention of two quite different segments of the nonscientific public: animal welfare and animal rights or animal liberation groups. Animal welfare groups are concerned not only about laboratory research involving living animals, but also about other aspects of animals’ involvement in human society. In contrast to animal welfare groups, animal rights groups argue that no laboratory research should involve living animals, regardless of the benefits that would result from animal research.

• The human brain, with its 100 billion neurons, is the most complex of all biological organs. It is this physical organ that controls our behavior, feelings, and thought. The modern study of brain and mind has emerged as a vital part of contemporary science. Philosophically, the biological approach to psychology that characterizes contemporary behavioral neuroscience is realistic (believing that reality is based in the physical universe), empirical (based upon sensory information), monistic (holding that mind and brain are the same), and reductionistic (attempting to explain mind in terms of its underlying neural mechanisms).
• To understand mind and behavior as an aspect of biology, multiple levels of scientific analysis are required. This includes analyses of what it is that the organism is attempting to do, the procedure or plan for meeting that objective, and the neural mechanisms by which the selected procedure is implemented. This multilevel approach is necessary in studying complex systems such as the human brain.
• The striking advances of modern brain research may be attributed to the use of the scientific method, which is reality a general approach to problem solving. It emphasizes objectivity, careful observation, and well-designed experimentation. The use of appropriate experimental controls and adequate statistical treatment of data are also important. But it is the independent verification of results that provides the final insurance of relative objectivity in scientific research. The scientific study of the brain and behavior is marked by the evolution of both experimental methods and theoretical concepts.
• Increasingly, the study of the brain and behavior has become an interdisciplinary endeavor. Old distinctions, based on divisions between the traditional academic disciples, are dissolving; today’s brain researchers think of themselves as neuroscientists.