Characterization of the Neural Codebook in an Invertebrate Sensory System


Book Description

The stimulus feature selectivity, timing precision and coding characteristics of two bilateral pairs of primary sensory interneurons of the cercal system were characterized using three novel techniques. First, estimates of the cells' feature selectivity that take the natural variance in stimulus-response latency (i.e., spike 'jitter') into account were derived. Second, the cells' stimulusresponse relationship was probed for specific non-linear aspects that could constitute 'temporal' encoding. Third, an iterative stimulation paradigm was used to test and refine the predictions of the cercal system's stimulus selectivity. Compared to earlier characterization of this system, these new analytical procedures yield significantly different estimates of the stimulus feature selectivity of these cells. A 'code book' for the stimulus-response characteristics of these cells is presented, with emphasis on demonstrating instances where a cell represents different stimuli with distinct spike 'code-word' patterns.




Coding Properties in Invertebrate Sensory Systems


Book Description

Animals rely on sensory input from their environment for survival and reproduction. Depending on the importance of a signal for a given species, accuracy of sensory coding might vary from pure detection up to precise coding of intensity, quality and temporal features of the signal. Highly sophisticated sense organs and related central nervous sensory pathways can be of utmost importance for animals in a complex environment and when using advanced communication systems. In sensory systems different anatomical and physiological features have evolved to optimally encode behaviourally relevant signals at the level of sense organs and central processing. The wide range of organizational complexity, in combination with their relatively simple and accessible nervous systems, makes invertebrates excellent models to study general sensory coding principles. The contributions to this e-book illustrate on one hand particular features of specific sensory systems, and on the other hand indicate not only common features of sensory coding across invertebrate phyla, but also similar processing principles of complex stimuli between different sensory modalities. The chapters show that the extraction of behaviourally relevant signals from all environmental stimuli, as well as the detection of low intensity signals and the analysis of temporal features can be similar across sensory modalities, including olfaction, vision, mechanoreception, and heat perception.




Coding Properties in Invertebrate Sensory Systems


Book Description

Animals rely on sensory input from their environment for survival and reproduction. Depending on the importance of a signal for a given species, accuracy of sensory coding might vary from pure detection up to precise coding of intensity, quality and temporal features of the signal. Highly sophisticated sense organs and related central nervous sensory pathways can be of utmost importance for animals in a complex environment and when using advanced communication systems. In sensory systems different anatomical and physiological features have evolved to optimally encode behaviourally relevant signals at the level of sense organs and central processing. The wide range of organizational complexity, in combination with their relatively simple and accessible nervous systems, makes invertebrates excellent models to study general sensory coding principles. The contributions to this e-book illustrate on one hand particular features of specific sensory systems, and on the other hand indicate not only common features of sensory coding across invertebrate phyla, but also similar processing principles of complex stimuli between different sensory modalities. The chapters show that the extraction of behaviourally relevant signals from all environmental stimuli, as well as the detection of low intensity signals and the analysis of temporal features can be similar across sensory modalities, including olfaction, vision, mechanoreception, and heat perception.










Plasticity in the sensory systems of invertebrates


Book Description

The visual, olfactory, auditory and gustatory systems of invertebrates are often used as models to study the transduction, transmission and processing of information in nervous systems, and in recent years have also provided powerful models of neural plasticity. This Research Topic presents current views on plasticity and its mechanisms in invertebrate sensory systems at the cellular, molecular and network levels, approached from both physiological and morphological perspectives. Plasticity in sensory systems can be activity- dependent, or occur in response to changes in the environment, or to endogenous stimuli. Plastic changes have been reported in receptor neurons, but are also known in other cell types, including glial cells and sensory interneurons. Also reported are dynamic changes among neuronal circuits involved in transmitting sensory stimuli and in reorganizing of synaptic contacts within a particular sensory system. Plastic changes within sensory systems in invertebrates can also be reported during development, after injury and after short or long- term stimulation. All these changes occur against an historical backdrop which viewed invertebrate nervous systems as largely hard-wired, and lacking in susceptibility especially to activity-dependent changes. This Research Topic examines how far we have moved from this simple view of simple brains, to the realization that invertebrate sensory systems exhibit all the diversity of plastic changes seen in vertebrate brains, but among neurons in which such changes can be evaluated at single-cell level.




Sensory Coding in the mammalian nervous system


Book Description

Great advances have been made in the area of sensory physiology during the last few decades, and these developments seem to be asking for a comprehensive review that is manageable in size and cohesive in content. This volume has been written with that goal in mind. In the first place I would like to thank Mr. R. van Frank of Appleton-Century-Crofts for asking me to do the job, and my wife for persuading me to do it, for writing it was an enjoyable task. Much of the discussion of factual data set to print here evolved in question-and-answer sessions in courses given to students in physiology, psychology, and medicine, and to physicians training in neurology, neurosur gery, and psychiatry. Besides my students, I had in mind while preparing this text my professional colleagues laboring on their lecture notes under circum stances perhaps not unlike my own. The material is divided in two parts. The first deals with the manner of representation of sensory information in peripheral nerves: the so-called first order code. The second half of the text deals with the handling of sense data by the central nervous system. One reason for dividing the material in this way is that many of the features of the first-order code are common to all sensory modalities. The intensity, the place, the rhythm, the "quality" of stimuli are encoded by rules which are applicable, albeit with appropriate modifications, to all senses. Furthermore, these rules of coding are today rather well understood.




Invertebrate Learning and Memory


Book Description

Understanding how network mechanisms contribute to behavioral plasticity is a key objective in learning and memory studies. This is likely to be complex because the different types of synaptic and nonsynaptic (cellular and neuronal) changes that underlie memory are known to occur at multiple locations within the neural network. Determining how these multiple changes are integrated to generate network correlates of learning is the major goal of a systems analysis. Gastropod mollusks offer the advantage that behavioral plasticity can be directly linked to network and the cellular analysis of learning because of the ability to identify individual neurons and determine their synaptic connectivity. Important progress has been made in understanding the synaptic and nonsynaptic contributions to network changes underlying simple forms of nonassociative (habituation and sensitization) and associative (classical and operant conditioning) learning and, to a lesser extent, more complex types of behavior such as second-order conditioning.




Invertebrate Learning and Memory


Book Description

What is the engram, the memory trace that stores the content of memory? Here, I argue that the engram is more than just the sum of all learning-related neural changes. Rather, it is an integrated part of the whole nervous system, from sensory integration to interneuron processing and motor control. Emphasis is given to those neural processing components that do not express themselves in the behavior of the animal. To date, the search for the olfactory engram in the bee brain has focused on network properties in the antennal lobe (AL), the input and output regions of the mushroom body region (calyx), the mushroom body extrinsic neurons, and the reward pathway. I conclude that the olfactory memory trace in the AL relates predominantly to attention-generating properties. The memory trace in the calyx is characterized by the high-order combinatorial integration of multiple sensory inputs. Mushroom body extrinsic neurons are tentatively related to multiple processing categories that represent the acquired values (e.g., favorable conditions and to be avoided condition) and provide neural commands for goal-directed behavior and decision making. The system of VUM neurons stores appetitive memory related to appetitive internal states and controls nonassociative and associative memories. A model is presented that aims to capture the multifaceted and distributed nature of the engram and may help to guide our future search of the engram at a systems level.




Nervous Systems in Invertebrates


Book Description

The idea of holding an Advanced Study Institute (ASI) and getting a volume out, on the Nervous Systems in Invertebrates first cropped up in the summer of 1977 at the ASI on Sensory Ecology. I had prepared a review of the nervous systems in coelomates and noticed how much we depended on Bullock and Horridge's treatise on the one hand and how much new material and requirements has cropped up since 1965, when this classical work was published. Interest in the concerted study of pollution and environmental toxicology was growing in geometrical proportions and the use of invertebrates as indices was growing. As a teacher of a course on the biology of invertebrates since the beginning of my career I had also noticed how the interest of the students and the content of my course was shifting gradually and steadily from the traditional morphology-taxonomy type to the physiology-ecology-embryology orientation. Students were demanding to know the relevency of what they had to learn. Thus, after the ASI on Photoreception and Vision in Invertebrates held in 1982 the question of one on nervous systems was raised by a number of colleagues. It appeared then that the consensus was that the time was ripe to hold one and that it will be worthwhile. Therefore, as usual arrangements had to begin at least two years in advance. Most of the persons I contacted to lecture and write chapters on selected topics agreed enthusiastically.