Curt Richter and the behavioral control of homeostasis
RICHTER CP, Total self-regulatory functions in animals and human beings. Harvey Lecture Series 38: 63-103; 1943.
Comments by Nori Geary (December 20, 2013)
In this consensus classic, Curt Richter summarizes the results of roughly the first third of his long career. There is no false modesty. Richter places himself – appropriately so[2,3] - together with Claude Bernard and Walter Cannon in the pantheon of heroes of homeostasis for his demonstration that behavior plays a key role in homeostasis. The first example Richter brings in support of his thesis is adrenalectomy-induced sodium appetite. This example has five classic Richterian elements: (1) a wealth of data, emphasizing individual more than group data, establishing that (2) behavior contributes importantly to homeostatic regulation, (3) that nutritional deficits can lead to compensatory changes in dietary nutrient selection, (4) that homeostatic behaviors are often integrated with and controlled by endocrine function, and (5) that such behaviors are important in humans as well as other animals.
Later Richter did pioneering work on biological rhythms and the autonomic nervous system, especially its role in stress responses. His endocrine and stress work form the foundation of behavioral endocrinology. Subsequent methodological advances have permitted extending the analyses of neuroendocrine controls of behavior in many ways, most notably into the brain, but the conceptual basis is the same. These contributions are recognized by the International Society of Psychoneuroendocrinology’s annual Curt Richter Award.
Part of Richter’s genius was practical. He designed a number of ingenious contraptions to detect, among others, eating and drinking, dietary selection, locomotor and general activity, and nest building. He was particularly attracted to behavioral changes elicited by lesions of endocrine glands and developed and mastered a number of surgical methods for extirpation of the adrenal, parathyroid and other glands.
Richter was an autodidact and a fiercely independent researcher. There are several sketches of his way of thinking and working [5-9], all very enlightening. The insight, originality and self-assuredness that Richter demonstrated throughout his career is reflected in a famous anecdote. Richter began training as an engineer, his father’s profession, but left it, and entered Harvard College, where he was a generally indifferent student. However, he was intrigued by idea of an objective approach to behavior after having read “only snatches here and there” of John B. Watson’s book Animal Behavior, and applied to work with Watson as a graduate student at Johns Hopkins University. Soon after Richter’s arrival there in 1919, Watson rolled a rack of rats into his office and told him to do something interesting with them. What Watson expected, of course, was that Richter would teach the rats in some interesting way. Watson’s view was that learning was the only interesting thing in psychology; he wrote famously “Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.” So what did Richter do? He turned Watson on his head: “From a cursory observations of the rats, I decided that I might work on their spontaneous activity. This spontaneous activity fascinated me” (underlining added). Internal drives continued to absorb Richter to the tune of nearly 400 publications over 66 years in the very same lab.
How has his work stood the test of time? Richter’s main thesis, that behavior contributes to homeostasis, is scientific canon. His interest in specific appetites, his general designs and his data also hold up well. Many of the appetites first described by Richter, including sodium[12-16], calcium, vitamin B, protein  and others, remain active areas of the neuroendocrinology of ingestive behavior. On the other hand, his favorite mechanistic hypothesis, that specific appetites are exclusively mediated by changed sensory thresholds, has given way to recognition of the overriding importance of learned and hedonic mechanisms.[5,13,15,17,18] In addition, two general limitations of Richter's approach gradually emerged. First, he focused on the arousal of appetites in a deficit states without considering the possibility that the satiation of appetite might be equally important for homeostasis. As the widespread excesses in energy and sodium intake displayed in epidemic proportions in today's world clearly show, satiation of motivation is a crucial issue. Second, in comparison to its successes in the analysis of appetites elicited by explicit deficits, Richter's program did not gain much traction on the problem of appetites that emerge in the absence of any identifiable deficit, such as spontaneous eating.
Richter was also a proponent of what is now known as translational research. As he notes, his work on self-selection of dietary sources of micro- and macronutrients dovetailed with the heroic, but scientifically (and by current standards ethically) flawed contemporaneous studies of Clara Davis suggesting that infants and young children self-selected a healthy diet. Richter was too good a scientist to accept Davis’ sketchy reports, but nonetheless her data led him to investigate the appetite for vitamin D, as reflected in children’s liking for cod-liver oil. As far as I know, this fascinating result has not been pursued at either the basic or clinical level.
Interestingly, in contrast to his emphasis of homeostatic controls of food selection, Richter comments in this Ingestive Classic only briefly on controls of total energy intake, a major focus of contemporary research on behavioral homeostatic mechanisms. Another gem in his review, however, suggests an important interaction of energy and specific nutrient homeostasis. Richter showed that pregnant rats self-selecting from an array of purified diets ate about 20% less overall than rats fed a balanced stock diet, apparently without any effect on the weight and vitality of the offspring. Furthermore, during lactation, self-selecting rats ate 50% less overall, but more protein, fat, sodium, calcium and phosphorus. Given the importance of energy and nutrient homeostasis for the health of mother and child[20-22], this seems to me one of Richter’s findings most worthy of pursuit.
In conclusion, Curt Richter was one of the great pioneers of the objective study of biologically motivated behavior, whose work is a cornerstone of our field. Because of his unparalleled originality and the breath and depth of his work, his writings remain fascinating and valuable.
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