Annales de la faculté des sciences de Toulouse Mathématiques

de Castro J.M.

Porte D.

Stephan F.K.

In the battle against entropy, living organisms require sufficient energy intake to survive long enough to reproduce. Consequently, strong selective pressures must have shaped efficient feeding strategies. For foraging omnivores and carnivores, some food sources may be available only during temporal windows within the day and these may change during seasons. For herbivores, food sources are more constant on a daily basis, but it may be advantageous to feed only at certain times of day to avoid predators. Thus, the time of food availability and the time of feeding can be important factors in survival. In addition to relying on external geophysical cues, animals can use endogenous circadian clocks to generate optimal temporal patterns of behavior, including feeding. The purpose of this chapter is to present evidence that many mammals have a separate circadian clock system that responds to food, rather than to light, as a zeitgeber.

Blumberg M.S.

Developmentalists are concerned with origins. For some, the search for origins in developing animals provides little more than an opportunity to clarify the factors that contribute to adult behavior and physiology. Although this is an understandable justification for developmental research, it is also important to understand that developing organisms are not simply small adults or adults-in-waiting. On the contrary, infant animals face many problems that are unique to their physical, physiological, social, and ecological circumstances ([Alberts & Cramer, 1988]; [Hall & Oppenheim, 1987]; [West, King, & Arberg, 1988]). These problems cannot be put off; rather, to survive, infants must solve each problem as it is encountered during ontogeny. Therefore, the “dual infant” must meet the needs of the moment as well as prepare for later life, a vital combination of adaptation and anticipation ([Alberts & Cramer, 1988])

Daan S., Aschoff J.

The entrainment of circadian systems is essential for their functional significance as well as for our insight into their physiologic organization. Entrainment entails the adjustment of both the frequency and phase of rhythms in the living world to the cycle of the earth’s rotation. It is only by virtue of entrainment that programs in behavior and physiology produced by endogenous circadian systems can be properly timed. This is crucial for the advantages in natural selection that in the past gave rise to the evolution and today maintain the genetic basis of these systems. Entrainment requires the sensitivity of endogenous oscillators toward particular environmental cues as well as insensitivity toward others. The sensitivity toward light has been and continues to be a primary guide in probing and unraveling the physiology of circadian systems.

Hirsch H.V., Tieman S.B., Barth M., Ghiradella H.

Programs guiding nervous system development must achieve two goals. First, they must generate the species-specific behaviors needed for survival and procreation. Second, they must incorporate into the nervous system information about the environment in order to “tune” the organism to current conditions. Such “experience-dependent assembly” of the nervous system has long been seen as a hallmark of development among the vertebrates (especially mammals), whereas “hardwiring” and inflexibility were seen as hallmarks of development among invertebrates

Hogan J.A.

The purpose of this chapter is to present a general framework for studying the development of behavior. The thesis to be defended here is that the building blocks of behavior are various kinds of perceptual, central, and motor components, all of which can exist independently. The study of development is primarily the study of changes in these components themselves and in the connections among them

Meijer J.H.

The rotating earth imposes a rhythm of more or less 24 hours upon environmental conditions. The resulting changes in physical environment are drastic, but predictable. Organisms time their behavior in synchrony with the environmental changes and show clear rhythmic patterns in activity, temperature, food intake, etc. For a long time it was assumed that the daily timing of animal behavior was dictated by the 24-hour light—dark cycle. However, when Johnson (1939) recorded mice that were kept in constant darkness, he noticed that their activity pattern was still rhythmic, but the period of the cycle was now slightly different from 24 hours. He therefore concluded that the origin of circadian rhythms should be sought inside animals, and postulated a “self-winding” physiologic clock.

Weller A.

This chapter examines the ontogeny of motivated behavior, particularly the origins of early attractions. It focuses on the biological foundations of preferences in an animal model, the laboratory rat. A developmental approach is utilized to examine the appearance over ontogeny of different behavioral tendencies and how they change. This approach can reveal components of motivation as they appear (at different ontogenetic times) and allow the examination of the physiological substrate (hormonal, neural, etc.) of these developing components separately. This approach can also specify how experience contributes to motivational change by building on states that are, by definition, rewarding to newborns. These states, concerned with energy conservation and with stimulation of the central nervous system (CNS) for brain growth and development, will be discussed and the position advanced here of intrinsically rewarding systems will be supported.

Page T.L.

The study of the anatomic and physiologic organization of circadian systems of invertebrates has a long and productive history. Modern research can be traced to the work of Janet Harker in the 1950s, who initiated efforts to localize pacemakers and photoreceptors of the circadian system of the cockroach via lesion and transplantation studies. Ultimately, Harker was not successful, but the questions and approaches she pioneered set the stage for subsequent efforts to identify components of invertebrate circadian systems. These efforts have been directed toward answering several fundamental questions about the organization of the circadian system which are the focus of this review. The first of these concerns the nature of the pacemaking system that generates the timing signal. What are the anatomic loci of component oscillators, what is the significance of multioscillator organization, and how does the pacemaking system emerge in development? Second, what are the pathways and mechanisms by which inputs to the pacemaking system regulate its phase and period? Finally, what are the neural and endocrine signals by which the pacemaking system regulates the various processes under its control?

Burghardt G.M.

Play is an important aspect of neurobehavioral development. While many agree (e.g., [Byers, 1998]; [Fagen, 1981]), the lack of attention to play has prompted one eminent neuroscience researcher to write, “It is sad that play research has not been of greater interest for neuroscientists… the modern search for the mythological fountain of youth’ should focus as much on the neurobiological nature of mental youthfulness and play as on ways to extend longevity” ([Panksepp, 1998], p. 281). Underscoring the dearth of work in this area, a major compendium on cognitive neuroscience ([Gazzaniga, 1995]) lacks a single index reference to play, curiosity, or even exploration! To add another small voice to the call to make play a fruitful neurobiological pursuit, the present review develops and extends themes of play that I have broached previously in this format ([Burghardt, 1988]), but more specifically addresses neurobiological correlates. The evolutionary neural model of play suggested below in broad strokes is presented here in a condensed, verbal manner. It is an uneasy union of a developmental proximate scheme (the mechanisms and ontogenic processes of play in individuals) with an evolutionary scheme (how play originated in ancestral species and diversified, gaining new functions facilitating behavioral, emotional, and cognitive complexity).

Moore R.Y., Leak R.K.

The suprachiasmatic nucleus (SCN) is a prominent feature of the anterior hypothalamus. In virtually all mammals, the SCN is a compact group of small neurons dorsal to the optic chiasm along most of its length and just lateral to the periventricular nucleus and third ventricle (Figure 1). The SCN was recognized in early cytoarchitectonic studies (Brockhaus, 1942; Gurdjian, 1927), but its function remained obscure until the early 1970s. Perhaps the first hint was a report by Pate (1937), who observed what must be considered transneuronal atrophy of the SCN after eye removal in the cat. The issue of retinohypothalamic projections in mammals was contentious in that era and the great neuroanatomist W. J. H. Nauta concluded in the late 1960s that there were no compelling data to support such a projection. This conclusion, however, was contrary to the situation in lower vertebrates, where a projection from the retina to the suprachiasmatic area was well established (Ebbeson, 1970). As often happens, new technical advances provided the basis for new understanding. The discovery of anterograde transport by Weiss and colleagues (Weiss, 1972) was dependent upon the fact that tritiated amino acids are incorporated into proteins in neuronal perikarya and then transported through axons to sites of terminal arbors. This phenomenon formed the basis for an axoplasmic tracing method to analyze connections in brain (Cowan, Gottlieb, Hendrickson, Price, & Woolsey, 1972) and this was applied to the study of retinal projections, providing new evidence for a retinohypothalamic tract in mammals (Hendrickson, Wagoner, & Cowan, 1972; Moore, 1973; Moore & Lenn, 1972). In these studies, silver grains were found distributed over the ventral SCN, strongly suggesting that terminals of retinal axons were present in that location. This was confirmed by the electron microscopic finding of degenerating axon terminals synapsing on SCN neuron dendrites after eye removal (Moore & Lenn, 1972). These data, then, provided definitive evidence for a retinohypothalamic tract terminating in the SCN.

Kehoe P., Shoemaker W.

The fulfillment of an individual’s genome of the central nervous system ontogenetically involves a series of processes collectively termed developmental plasticity ([Perry & Pollard, 1998]). These processes govern cellular migration, synapse formation, and other aspects of the orderly development of the nervous system (Z. Hall, 1992). The term plasticity is used because of the presence and absence of transmitters, growth factors, and hormones that influence the appearance of cells and synaptic connections defining the species. Perturbations of these processes result in abnormal development ([Perry & Pollard, 1998]). Developing systems are not “fixed and immutable” but are susceptible to disturbances that reflect severity and point in developmental time ([Perry, 1997]). Experiential plasticity defines the neural changes that may occur following exogenous stimulation or social restriction. For fetuses and newborns experiential plasticity is superimposed upon the genetically synchronized developmental plasticity and both processes proceed simultaneously during early development. Experiential plasticity is understandable within the context of early stages of neural development; rate and asymptote of brain growth and maturity are very much dependent on environmental conditions and how those conditions impact the infant.

Holmes W.G.

Each year since 1904, the Carnegie Hero Fund Commission has presented a medal and financial award to civilians who voluntarily risked their own lives to save another person’s. The Hero Fund came about because, according to its founder, Andrew Carnegie, “I do not expect to stimulate or create heroism by this fund, knowing well that heroic action is impulsive; but I do believe that, if the hero is injured in his bold attempt to serve or save his fellows, he and those dependent upon him should not suffer pecuniarily” ([Carnegie, 2000]). One type of hero who is ineligible for an award is the hero who saves a member of his or her own immediate family. Why would the Commission exclude from the list of deserving heroes those who save a close genetic relative? I suggest that the reason is quite straightforward: we humans take for granted that our kin will come to our aid in times of need; self-sacrifice for a relative like a child, a sibling, or a niece is part of our “nature” and thus does not merit pecuniary reward ([Burnstein, Crandall, & Kitayama, 1994]). Still, why should this be so? One of my aims in this chapter is to explain the ubiquitous and deeply ingrained nature of nepotism that permeates human and nonhuman social relationships. My analysis may help provide a deeper biological understanding of why saving a friend or stranger might merit financial reward, whereas saving a close relative is “natural” and therefore would not

Hill D.L.

The developing gustatory system has the complex task of processing and organizing an ever-increasing array of sensory stimuli. During ontogeny animals must be able to recognize food and to appropriately reject toxic foods that induce adverse or lethal consequences at the age when they begin to sample substances from their environment. In response to toxic stimuli, the neural taste message should be accurate, reliable, and probably not change significantly with age. In contrast, the ability to have an alterable neural message to other food classes during development is adaptive. There are multiple examples of both “static” and “plastic” processing in the developing gustatory system, and much of this chapter is devoted to expanding upon these ideas and their implications. I also consider the gustatory system as a major component in energy homeostasis; it must meet changes in nutritive demands and developmentally related gastrointestinal processes with an accurate, complex processing of relevant sensory stimuli. It is this relatively unexplored aspect of the gustatory system that may have the greatest relevance during development.