cybernetics A term introduced by the mathematician N. Wiener (1894-1964) from the Greek kubernetes ("steersman"). This term, which defines a theory of feedback systems (namely, self-regulating systems), could be applicable not only to living systems but also to machines.

emotion From the earliest philosophical speculations onwards, emotion has often been seen as interfering with rationality, as a remainder of our presapiens inheritance: Emotions seem to represent unbridled human nature "in the raw." Emotions are the product of an individual's own processing of occurrences on the basis of his or her own prior history and biology, and emotional response activates neural and neuroendocrine effector systems and leads to a variety of short- and long-term consequences that may or may not result in disease.

homeostasis The physiologiste. Bernard (1813-1878)introduced the concept of the constancy of the milieu intérieur. This internal milieu ensures the biological unity of the organism and confers a certain autonomy relative to the external milieu. The term homeostasis was coined some years later by W. B. Cannon (1871-1945). He developed the concept of homeostasis, which in modern terminology is the feedback control of servo-systems. This concept was not mathematically expressed until the 1940s, when it became the basis of cybernetics. Today, the term homeostasis refers to the adaptative response of an organism and tends to be substituted by a newer term, allostasis, which means "stability through anticipatory change''; the long-term consequences of continued demand on the physiologic response are referred to as allostatic load.

hypothalamus A brain area that encompasses the most ventral part of the diencephalon where it forms the floor and, in part, the walls of the third ventricle. The hypothalamus consists of several nuclei that form a neuronal continuum. It plays a central role in homeostasis by controling the autonomic nervous system, the neuroendocrine system through its control of both the anterior and posterior parts of the pituitary gland, and the motivational states.

limbic system In 1878, P. Broca was the first to describe an annular ring of tissue on the medial face of the cerebral hemisphere that represents the free edge of the cerebral cortex. He named this part of the brain le grand lobe limbique ("the great limbic lobe"), which led to the concept of the limbic system. This system includes the hippocampal formation, entorhinal area, olfactory regions, hypothalamus, and amygdala. Functionally, the limbic system is generally thought to be concerned with visceral processes, particularly those associated with the emotional status of the organism. In fact, the interaction of all the structures in the complex, from the entorhinal area to the hypothalamus, plays a major role in the elaboration of the final actions of an organism in a particular environment and in the formation of adaptive behavior patterns.

How does the body adapt to environmental conditions? How does it organize its reactions to the world and other people? What are desire, pleasure, and pain? Going beyond the traditional dichotomies of body and soul, or reasonable brain and passionate body, we shall deal with what is called the constancy of the internal milieu for a human being brought by homeostatic mechanisms. Are we reductionist when we decide to approach the molecular mechanisms of our emotions? It must be recognized that while we announce that being is not just the sum total of the parts of the machine, this very machine shows itself to be increasingly complex as it gradually yields the secrets of its inner workings. It is indeed astonishing that we can analyze networks of billions of interconnected elements of an extraordinary

Encyclopedia of the Human Brain Volume 2

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complexity and at the same time develop a single molecule capable of causing or correcting the most inextricable disorders of the mind. Therefore, the scientist is not the only one accused of reductionism: Nature provides an example of radical simplification.

Even a unicellular being has a certain degree of freedom between the information receptors on the cell surface and the effectors on the inside. The evolution of a species consists of a gradual increase in the number of intermediaries between information from the outside world and effectors responsible for actions. An animal's freedom increases in proportion to the number of these intermediaries. However, it is only because the liquid element and the substances it transports bring a solution of continuity to cell organization that this freedom is possible.

We shall therefore deal with the constancy of the internal milieu. The external milieu was a Greek invention, but the concept of internal milieu was introduced by C. Bernard (1813-1878). For Greek doctors and their disciples, man lived in harmony with nature. Temperament fixed the conditions of this harmony. However, the living being had no real identity or biological unity: The humors were nothing but a kind of reproduction, inside the animal, of the surrounding natural elements; there was no substantial difference between nutrients and living matter. The internal milieu ensures the biological unity of the animal and confers a certain autonomy relative to the external milieu. It is supposed to reconstitute around the cells the characteristics of the original marine environment.

In homeostasis, any departure from the norm draws mechanisms into play that tend to bring the trouble spot back to its initial state. Passions could thus be interpreted as a kind of neurosis of the normal, itself a fictitious immobile system of reference. In fact, behind the impassivity of the internal milieu a confused mesh of false constants is hidden, all of which are more or less dependent and variable from one species to the next, from one individual to the next, and, within each individual, from one situation to the next.

We can see the kind of safeguard that the constant agitation of the humors of the internal milieu offers the nervous system and its operational flexibility: Perhaps the brain runs the risk of falling victim (losing its soul?) to such a commotion. For its own protection, it can organize its own disorder: The brain-gland reveals itself as grand master of the humors by its multiple secretions of neurohormones. Like the brain-machine, the humoral brain simultaneously acts as the passionate victim and the orchestrator of its own passion.

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

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