THE LAST FRONTIER OF THE BIOLOGICAL SCIENCES—the ultimate challenge—is to understand the biological basis of consciousness and the brain processes by which we feel, act, learn, and remember. During the past few decades, a remarkable unification within the biological sciences has set the stage for addressing this great challenge. The ability to sequence genes and infer the amino acid sequences of the proteins they encode has revealed unanticipated similarities between proteins in the nervous system and those encountered elsewhere in the body. As a result, it has become possible to establish a general plan for the function of cells, a plan that provides a common conceptual framework for all of cell biology, including cellular neural science.
The current challenge in the unification within biology is the unification of psychology—the science of the mind—and neural science—the science of the brain. Such a unified approach, in which mind and body are not seen as separate entities, rests on the view that all behavior is the result of brain function. What we commonly call the mind is a set of operations carried out by the brain. Brain processes underlie not only simple motor behaviors such as walking and eating but also all the complex cognitive acts and behavior that we regard as quintessentially human—thinking, speaking, and creating works of art. As a corollary, all the behavioral disorders that characterize psychiatric illness—disorders of affect (feeling) and cognition (thought)—result from disturbances of brain function.
How do the billions of individual nerve cells in the brain produce behavior and cognitive states, and how are those cells influenced by the environment, which includes social experience? Explaining behavior in terms of brain activity is the important task of neural science, and the progress of neural science in this respect is a major theme of this book.
Neural science must continually confront certain fundamental questions. What is the appropriate level of biological description to understand a thought process, the movement of a limb, or the desire to make the movement? Why is a movement smooth or jerky or made unintentionally in certain neurological disease states? Answers to these questions might emerge from looking at the pattern of DNA expression in nerve cells and how this pattern regulates the electrical properties of neurons. However, we will also require knowledge of neural circuits comprising many neurons in specific brain areas and how the activity of specific circuits in many brain areas is coordinated.
Is there a level of biological description that is most apt? The short answer is, it depends. If one’s goal is to understand and treat certain genetic epilepsy disorders, then DNA sequencing and measurements of electrical properties of individual neurons might be sufficient to produce an effective therapy. If one is interested in learning, perception, and exploration, then an analysis of systems of circuits and brain regions is likely to be required.