Neuroethology

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Author: Dr. Günther K. H. Zupanc, Jacobs University, Germany

Neuroethology refers to the study of the neural basis of natural behavior in animals

1 History and key principles
2 Model systems
3 Textbooks
4 Journals
5 Professional Society
6 References
7 External links

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History and key principles

Neuroethology is a multidisciplinary area of study that emerged as an independent scientific discipline in the 1970s and 1980s. This rather late development contrasts with the history of its two foundation disciplines, neurobiology and ethology. The beginnings of modern neurobiology can be dated back to the end of the nineteenth century after the histological studies of Santiago Ramón y Cajal (1852-1934) had provided experimental evidence in favor of the cell theory as an adequate description of the organization of the nervous system. Ethology was formally established between the 1930s and 1950s, particularly through the work of Konrad Lorenz (1903-1989) and Niko Tinbergen (1907-1988).

One reason for the late development of neuroethology lies in the lack of proper methodology and suitable model systems. Traditionally, neurobiologists have worked on anesthetized animals, or isolated parts of nervous tissue, or even single cells. The species is typically chosen based on technical considerations, such as the ease by which a favorable preparation can be obtained. For example, the classical investigations in the late 1940s and early 1950s of Alan Lloyd Hodgkin (1914-1998) and Andrew Fielding Huxley (born 1917) of the physicochemical factors that define the resting potential of neurons, and the generation and propagation of the action potential, were possible only by using preparations of particularly large, and readily accessible, axons, such as the squid giant axon.

By contrast, ethologists employ a whole animal approach. Preferably, they study the behavior of an animal in its natural habitat, avoiding disturbance by the experimenter as much as possible. If investigations in the laboratory are performed, the animal is kept under conditions mimicking those in the natural habitat as closely as possible. Many of the behaviors studied are rather complex, often occurring in the context of social interactions between conspecifics.

Obviously, combination of these two rather diametric approaches has been difficult, and continues to be challenging. For example, to explore the involvement of certain, anatomically defined brain areas in the control of specific behaviors it was necessary to electrically stimulate the brain of awake, freely moving animals. This became possible after Walter Rudolf Hess (1881-1973) developed in the late 1920s the focal brain stimulation technique to examine how regions within the diencephalon control vegetative functions in cats. First successful attempts to employ such an approach in an ethological context were made by Erich von Holst (1908-1962), in collaboration with one of his research associates, Ursula von Saint-Paul, in the late 1950s and early 1960s. By stimulation of discrete areas in the hypothalamus of alert chicken, they were able to evoke specific, and sometime even quite complex, behavioral patterns.

Another important step toward the establishment of neuroethology as an independent discipline was the focus on rather simple behaviors. However, especially in the early stages of neuroethology, these behaviors were often part of vegetative functions, instead of being displayed in a social context so that they were largely ignored by ethologists. For example, neuroethologists have intensively studied rhythmic movements of intestines. Although hardly any ethologist pays attention to such motor activities, the definition of important neuroethological concepts, such as the one of central pattern generators, would not have been possible without these investigations.

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Model systems

Like in many other biological disciplines, neuroethological research crucially depends on the choice of suitable model systems. Ideally, the behavior under scrutiny should be simple, robust, readily accessible, and ethologically relevant. Thus, such behaviors are exhibited not only under natural conditions, but they can also be evoked without much difficulty, and even on repeated occasions, upon presentation of a proper stimulus under standardized laboratory conditions. Furthermore, these behavioral patterns are clearly defined so that quantitative analysis is possible. The animal displaying such behaviors should be inexpensive, and suitable for keeping and breeding in the laboratory. Furthermore, the neural network underlying the behavior should be simple in the sense that it consists of a rather low number of neurons, and that these neurons form not too many different classes of nerve cells.

Due to the restrictions in obtaining neurophysiological recordings from moving animals, often the only way to monitor the neural activity associated with the perception of sensory stimuli relevant for eliciting a given behavior, or with the generation of the corresponding motor activity, is to use immobilized animals. Such animals can still perceive and process sensory stimuli, and may still be able to generate the neural activity associated with the production of the motor action. However, instead of displaying the real behavior, these animals produce fictive behaviors. For example, tadpoles of the clawed-toad (Xenopus laevis) produce a well-characterized behavior called escape swimming upon sensory stimulation during the first day after hatching. The neural activity of the circuitry in the spinal cord that controls this behavior can be studied in animals that are immobilized by blocking synaptic transmission at the neuromuscular junction with alpha-bungarotoxin (a constituent protein of the venom of the Southeast Asian Krait, Bungarus multicinctus). The study of such fictive swimming in tadpoles has enabled investigators to identify universal mechanisms that control rhythmic motor patterns in vertebrates.

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Textbooks

The first textbook of neuroethology was Neuro-Ethologie: Einführung in die neurophysiologischen Grundlagen des Verhaltens by Jörg-Peter Ewert, published in German by Springer-Verlag (Berlin/Heidelberg/New York) in 1976. An English edition entitled Neuroethology: An Introduction to the Neurophysiological Fundamentals of Behavior appeared in 1980. This textbook was an important step toward the formal establishment of neuroethology as an independent discipline.

Currently, two major textbooks are available for teaching neuroethology courses at the undergraduate and/or graduate level:

Thomas J. Carew: Behavioral Neurobiology: The Cellular Organization of Natural Behavior. ISBN 0-87893-092-2. 419 pages. Sinauer, Sunderland, Massachusetts (2000)

Günther K.H. Zupanc: Behavioral Neurobiology: An Integrative Approach. Foreword by Theodore H. Bullock. ISBN 0-19-870056-3. 342 pages. Oxford University Press, Oxford/New York (2004)

A Japanese edition of the latter was published by Springer-Verlag:

Günther K.H. Zupanc: Behavioral Neurobiology: An Integrative Approach. Foreword by Theodore H. Bullock. Japanese Edition. 276 pp. ISBN 978-4-431-72734-7 Springer-Verlag, Tokyo (2007)

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Journals

At present, there is no journal on the market that is exclusively devoted to the publication of neuroethological research. Instead, articles appear in a large number of scientific journals in the wider fields of animal behavior and neurosciences. The two journals that have, arguably, played the most important role in the publication of neuroethology papers are

Brain, Behavior and Evolution, edited by Walter Wilczynski, and published by S. Karger, Basle (Switzerland)

Journal of Comparative Physiology-A, edited by Friedrich G. Barth, Kentaro Arikawa, John G. Hildebrand, Peter N. Narins, Hans-Joachim Pflüger, and Günther K.H. Zupanc, and published by Springer-Verlag, Berlin/Heidelberg (Germany)

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Professional Society

The professional society devoted to the promotion of neuroethology is the International Society for Neuroethology (ISN). It was founded during a NATO-sponsored Advanced Study Institutes meeting (organized by Jörg-Peter Ewert, Robert R. Capranica, and David J. Ingle) on Advances in Vertebrate Neuroethology in Kassel (Germany) in 1981. First president of the ISN was Theodore H. Bullock. Its first congress, organized by Kiyoshi Aoki, was held in Tokyo (Japan) in 1986. Since then, meetings have taken place every three years at various locations in the world.

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References

Arshavsky, Y.I., Orlovsky, G.N., Panchin, Y.V., Roberts, A., and Soffe, S.R. (1993) Neuronal control of swimming locomotion: analysis of the pteropod mollusc ‘’Clione’‘ and embryos of the amphibian Xenopus. Trends in Neuroscience, 16, 227-233.