Wooden sculpture of the itinerant Buddhist monk Kūya. This portrait by the 13th century sculptor Kōshō shows the monk reciting the nembutsu, or praise of the Buddha, which in Japan takes the form of six characters. Kuya taught that focused recitation of the nembutsu would lead to rebirth in the Pure Land, a state of spiritual illumination. The six small Buddhas issuing from his mouth represent the six syllables of the spoken prayer. This portrayal shows remarkable complexity of representation, with pieces of wood carved in the shape of figurines, symbolizing discrete components of speech, which together represent language, its underlying concept, and in this case a means to spiritual enlightenment. (Reproduced, with permission from Rokuharamitsuji-temple, Kyoto, Japan.)
Motor and sensory functions take up less than one-half of the cerebral cortex in humans. The rest of the cortex is occupied by the association areas, which coordinate events arising in the motor and sensory centers. Three association areas—the prefrontal, parietal-temporal-occipital, and limbic—are involved in cognitive behavior: speaking, thinking, feeling, perceiving, planning, learning, memory, and skilled movements.
Most of the early evidence relating cognitive functions to the association areas came from clinical studies of brain-damaged patients. Thus, the study of language in patients with aphasia yielded important information about how human mental processes are distributed in the two hemispheres of the brain and how they develop.
Genetic manipulation in experimental animals can now be used to evaluate the relative contribution of genes and learning to specific types of behavior. Even the highest cognitive abilities have a genetic component. Composing music is an excellent example. Music conforms to complex, unusually abstract rules that must be learned, yet clearly it has genetic components intertwined with its learned aspects. The great composer Johann Sebastian Bach had many children, five of whom were distinguished musicians and composers. His only grandson also was a composer and harpsichordist to the court of Prussia. In 1730, Bach proudly wrote that he was able to "put on a vocal and instrumental concert with my own family."
Much of today's neural science concerns cognitive neural science, a merger of neurophysiology, anatomy, developmental biology, cell and molecular biology, and cognitive psychology—a merger that has given rise to a new science of mind. Until two decades ago the study of higher mental function was approached in two complementary ways: through psychological observation and through invasive experimental physiology. In the first part of the 20th century, to avoid untestable concepts and hypotheses, psychology became rigidly concerned with behaviors defined strictly in terms of observable stimuli and responses. Orthodox behaviorists thought it unproductive to deal with consciousness, feeling, attention, or even motivation.
By concentrating only on observable actions, behaviorists asked: What can an organism do, and how does it do it? Indeed, careful quantitative analysis of stimuli and responses has contributed greatly to our understanding of the acquisition and use of "implicit" knowledge of perceptual and motor skills. However, humans and other higher animals also have "explicit" knowledge of facts and events. Thus we also need to ask: What does the animal know about the world, and how does it come to know it? How is that knowledge represented in the brain? And does explicit knowledge differ from implicit knowledge? Much perhaps most, knowledge is unconscious a great deal of the time. We need to know the nature of the unconscious processes, the systems that mediate them, and their influence on the nature of conscious mental activity. Finally, we need to know about the highest realms of conscious knowledge, the knowledge of oneself as an individual, a thinking and feeling human being.
The modern effort to understand the neural mechanisms of higher mental functions began at the end of the 18th century when Franz Joseph Gall, a German neuroanatomist, proposed that particular mental functions are discretely localized in the brain. By the mid-19th century, clinical neurologists, who regarded their patients as "natural experiments" in brain function, studied brain lesions at autopsy to discover where particular brain functions were located. In 1861, Pierre Paul Broca, using evidence from the damaged brains of aphasic patients, convinced the scientific establishment that speech is controlled by a specific area of the left frontal lobe. Soon afterward the control of voluntary movement was localized, and the various primary sensory cortices for vision, audition, somatic sensation, and taste were delineated.
Neural science is only beginning to analyze the nature of the internal representations that cognitive psychologists have insisted intervenes between stimulus and response, and the very real dynamic unconscious mental processes studied by psychoanalysts—only now beginning to address the subjective sense of individuality, will, and purpose that is common to us all. In the past, ascribing a particular behavioral feature to a mental process that could not be directly observed meant that the process must be excluded from study because no reliable technique was available to examine brain function in the context of behavior. In Part IX, we show that because the nervous system and even its unconscious mental processes have become more accessible to behavioral experiments, internal representations of experience can be explored in a controlled manner.
A key concern of cognitive psychology and psychoanalysis is the relative importance of genetic and learned factors in forming a mental representation of the world. These disciplines can be strengthened by the insights into behavior that neuroscience now offers. The task for the years ahead is to produce a psychology still concerned with problems of mental representation, cognitive dynamics, and subjective states of mind but grounded firmly in empirical neural science.