This chapter looks at the active orientation mechanisms developed by some animals. The chapter focuses on echolocation, a mechanism to negotiate an animal's surroundings based on the emission of sound, its reflection by objects located within the emission beam, and the analysis of the returning echo. Echolocation has been found in bats, toothed whales, and oilbirds. The chapter revisits the beginning of echolocation research at the end of the eighteenth century when several scientists conducted a series of experiments on how bats orient in the dark. It describes the two major categories of sounds produced by bats: frequency-modulated (FM) signals which are used to estimate the distance of the bat from an object, and constant-frequency (CF) signals which are well suited for the so-called Doppler shift analysis. Lastly, the chapter discusses the adaptations developed by some insects to counteract bat echolocation.
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Active orientation and localization
Book
Günther K. H. Zupanc
Behavioral Neurobiology starts off with an introduction. The next chapter presents the fundamentals of neurobiology. The text also gives a brief history on the study of animal behavior and its neural basis, and examines orienting movements. Other topics covered include active orientation and localization, the neuronal control of motor output, the neuronal processing of sensory information, and sensorimotor integration. The text then goes on to consider neuromodulation and the accommodation of motivational changes in behavior, circadian rhythms and biological clocks, and large-scale navigation in terms of migration and homing, communication, and cellular mechanisms of learning and memory.
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Cellular mechanisms of learning and memory
This chapter focuses on the cellular mechanisms that underlie the memory stage. It explains amnesia, or the disturbance in long-term memory, manifested by total or partial inability to recall past experiences. The discussion distinguishes between anterograde amnesia and retrograde amnesia. The chapter then describes the two types of memory: explicit and implicit memories. It tackles the sensitization in the marine mollusk Aplysia as a model system to explain the cell biology of an implicit memory system. It discusses the neural circuit of the gill-withdrawal reflex and the molecular biology of both short-term and long-term sensitization. Furthermore, the chapter zooms in on the hippocampus of mammals and birds as a model to study the cell biology of an explicit memory system — explaining the concepts of long-term potentiation and adult neurogenesis.
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Circadian rhythms and biological clocks
This chapter addresses questions about how rhythms in animal behaviors and physiological activities are generated. It first looks at some of the major behavioral characteristics of rhythmic patterns occurring daily and finds out how the observations made during these studies have led to the concept of biological clocks. The discussion touches on the discipline of chronobiology, which examines biological rhythm. The chapter also explores the molecular structure of these clocks and discusses how the individual clock components integrate to produce an oscillatory output. Lastly, the chapter summarizes what is known about the localization of biological clocks at a systems level.
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Communication
This chapter reviews the biological definition of communication and some of the sensory modalities involved in the detection of communication signals. It explains the concepts of true communication and mutualism, as well as the sensory modalities involved in communication. The discussion covers visual, acoustic, chemical, tactile, and electrical signals. Furthermore, the chapter focuses on two intensively studied model systems. One of the model systems is the neuroethology of cricket song where the mechanism and neural control of sound production are examined, and the concept of positive phonotaxis is explained. The discussion covers the use of Kramer locomotion compensator, the song recognition by auditory interneurons, as well as the effect of temperature on calling songs of crickets. The second model system explains the development of bird songs — describing the neural circuits for song perception, song production, and song learning.
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Fundamentals of neurobiology
This chapter introduces the fundamentals of neurobiology, specifically the concepts and methodologies that are of immediate relevance to behavioral neurobiology. It discusses the cellular and subcellular composition of nervous systems – comparing cell theory and reticular theory. The discussion covers the Golgi method, an histological staining technique invented by Camillo Golgi, as well as the work of Spanish neurohistologist Santiago Ramón y Cajal who further improved the staining technique and applied it to many parts of the nervous system, providing strong evidence in support of cell theory. Furthermore, the chapter explains the salient features of neurons and nervous systems, the axons ensheathment by myelin, and the physiology and ionic basis of the electrical properties of neurons. It describes synapses, the specialized contact zones in the nervous system where a neuron communicates with another cell. The chapter also gives a glimpse of some neurobiological approaches in neuroethology.
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Introduction
This chapter gives an overview of neuroethology, the biological discipline that attempts to understand how the nervous system controls the natural behavior of animals. It emphasizes that this area of study has its roots in both neurobiology and ethology, and that its success is based on the incorporation of a blend of the neurobiological and ethological approaches into its own scientific armory. The chapter introduces ethogram, which refers to the entire behavioral repertoire of an animal species. Then it discusses how behavioral patterns are quantified using their rate of occurrence, duration, and/or intensity. The chapter also considers how to select a suitable model system for neuroethological research. These systems are characterized by behavioral patterns that, although simple, robust, and readily accessible, are also ethologically relevant.
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Large-scale navigation: Migration and homing
This chapter focuses on long-distance migrations of animals, introducing some key concepts of these phenomena. It discusses different modes of migration and briefly reviews previous experiments on the genetic control of migratory behavior. The chapter also explains homing, or the ability of an animal to specifically return to the place it considers home. Then it takes a closer look at the general methods used to study animal migration, including the use of tags, radar, and microtransmitters, and satellite-based radiotelemetry. Moreover, the chapter provides a detailed discussion of the behavioral, sensory, and neural mechanisms involved in orientation during migration and homing, using representatives of two particularly well-studied animal groups — birds and fish.
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Neuromodulation: The accommodation of motivational changes in behavior
This chapter discusses neural mechanisms that mediate motivational changes in the behavior of animals. It tackles the two major neural mechanisms that mediate motivational changes in behavior: structural reorganization of neural networks and biochemical switching of neural networks. The chapter considers some well-studied model systems to illustrate underlying principles. It explains dendritic plasticity by examining the seasonal changes in chirping behavior of weakly electric knifefish. It also discusses the seasonal variation in dendritic morphology of motoneurons in white-footed mice. Furthermore, it explains axonal or synaptic plasticity as a mechanism for accommodating variability in reproductive behavior during the estrous cycle of female cats. Then it reviews the modulation of the stomatogastric ganglion and the modulation of crayfish aggressive behavior to explain biochemical switching.
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Neuronal control of motor output
This chapter looks at different model systems that try to explain how coordinated contractions of muscles are controlled at the neural level. These muscle activities are associated with simple reflexes and rhythmic behaviors that often persist over long periods. The chapter reviews the model proposed by Charles Scott at the beginning of the twentieth century, which states that such coordinated activities are the result of a chain of reflexes, coordinated by proprioceptive information, in the spinal cord. The discussion also covers another major model proposed by Thomas Graham Brown, which assumes the existence of an intrinsic oscillator in the spinal cord that drives the coordinated activity of the muscles. Furthermore, the chapter tackles in detail the escape swimming behavior of Xenopus tadpoles relevant to the study of neural mechanisms involved in generating locomotor behavior.
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Neuronal processing of sensory information
This chapter looks at how organisms distinguish behaviorally relevant information from behaviorally irrelevant background noise, and how recognition of such behaviorally important information is achieved at the neural level. It uses two particularly well-examined model systems to provide effective illustrations: the recognition of prey and predators in the toad and the directional localization of sound in the barn owl. Before delving into the details of those models, the chapter first reviews some ethological concepts that are crucial in understanding how the sensory organs and the brain process behaviorally relevant sensory stimuli. It explains the concept of Umwelt, the part of the environment which is perceived after sensory and central filtering. It also sheds light on sign stimulus or the component of the environment that triggers a specific behavior. Furthermore, the chapter discusses the law of heterogeneous summation and the Gestalt principle.
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Orienting movements
This chapter examines how animals continuously collect and process relevant stimuli from the environment and translate them into proper behavioral action. It looks at the diversity of orienting movements in animals and summarizes the rules defining how to classify and name these movements. The discussion introduces concepts such as primary and secondary orientations of animals, as well as taxis and kinesis. The chapter then describes in more detail the cellular and neural mechanisms governing spatial orientation. Furthermore, it shows some model systems such as the taxis behavior in animal-like unicellular protist Paramecium species which exhibits chemotaxis, phobotaxis, and galvanotaxis, among others. The chapter also describes another model system, the geotaxis in vertebrates – a taxis behavior that involves the orientation of the body relative to gravity.
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Sensorimotor integration
This chapter focuses on sensorimotor integration or the transformation of the processed sensory input into proper motor action. It particularly looks at the jamming avoidance response of the weakly electric fish Eigenmannia as a model system that provides an excellent example to illustrate how sensory information and motor programs are integrated to generate a biologically important behavior pattern in response to a stimulus. Fish of this genus continuously generate, by means of an electric organ, wave-type electric discharges. The discharge rate is determined by the frequency of the pacemaker nucleus, an endogenous oscillator in the medulla oblongata. The fish sense their own electric currents, as well as those of neighbors, through electroreceptors. The chapter also discusses the electrosensory lateral line lobe, torus semicircularis, and nucleus electrosensorius.
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The study of animal behavior and its neural basis: A brief history
This chapter takes a closer look at the historical development of the study of animal behavior and neuroethology. It begins by discussing how anthropocentric approaches – the view that places humans as the most important element in the centre of the universe and interprets the world exclusively in terms of human values and experience – compromised the study of animal behavior. The chapter reviews the approach employed by Aristotle, considered the father of natural history and founder of zoology, in studying animals. It also introduces the mind-body dualism, a philosophical concept that holds perception, emotion, thoughts, and other mental phenomena as supernatural and not the result of brain activity. The chapter progresses to discuss evolutionary theory and comparative approaches in the study of animal behavior. It also explains how Konrad Lorenz and Niko Tinbergen founded the discipline of ethology, and the emergence of neuroethology at the end of the twentieth century.
