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Author: Mochi Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
One of the fundamental problems in neuroscience is how behavior is generated from sensory input and internal neural states, such as the animal?s behavioral context. We present new methods and findings to address this by studying the model organism Caenorhabditis elegans. With a fully mapped connectome of 302 neurons, this nematode is a particularly good candidate to investigate the neural basis of behavior due to its rich history of scientific research and its optical transparency. First, we showcase an instrument that can record panneuronal calcium activity in the head of a freely moving worm at single neuron resolution. We find multiple neurons have correlated activity with behaviors such as forward, backward, and turning locomotion. We also developed a high-throughput method to measure sensorimotor transformations from soft touch stimulation to locomotory behavior. We use automated behavior segmentation and reverse correlation to reveal how mechanosensory stimuli influences behavioral transitions. Our results show that C. elegans make locomotory decisions based on both the temporal history of the stimulus and its own behavioral context in a predictable manner. Continuing our investigation of the soft touch circuit, we developed a more advanced apparatus that can probe worm behavioral response to excitatory and inhibitory optogenetic stimuli with sub-animal level spatial resolution. This instrument has the ability to target the heads and tails of many animals in parallel, and can tailor the stimuli based on real-time behavior information. Preliminary experiments demonstrate that it can evoke the same optogenetically driven touch response akin to mechanical activation of the touch neurons.
Author: Mochi Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
One of the fundamental problems in neuroscience is how behavior is generated from sensory input and internal neural states, such as the animal?s behavioral context. We present new methods and findings to address this by studying the model organism Caenorhabditis elegans. With a fully mapped connectome of 302 neurons, this nematode is a particularly good candidate to investigate the neural basis of behavior due to its rich history of scientific research and its optical transparency. First, we showcase an instrument that can record panneuronal calcium activity in the head of a freely moving worm at single neuron resolution. We find multiple neurons have correlated activity with behaviors such as forward, backward, and turning locomotion. We also developed a high-throughput method to measure sensorimotor transformations from soft touch stimulation to locomotory behavior. We use automated behavior segmentation and reverse correlation to reveal how mechanosensory stimuli influences behavioral transitions. Our results show that C. elegans make locomotory decisions based on both the temporal history of the stimulus and its own behavioral context in a predictable manner. Continuing our investigation of the soft touch circuit, we developed a more advanced apparatus that can probe worm behavioral response to excitatory and inhibitory optogenetic stimuli with sub-animal level spatial resolution. This instrument has the ability to target the heads and tails of many animals in parallel, and can tailor the stimuli based on real-time behavior information. Preliminary experiments demonstrate that it can evoke the same optogenetically driven touch response akin to mechanical activation of the touch neurons.
Author: Andrea H. McEwan
Publisher: Elsevier Inc. Chapters
ISBN: 0128071575
Category : Medical
Languages : en
Pages : 53
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Book Description
Despite its apparent simplicity, the soil-dwelling nematode Caenorhabditis elegans has a surprisingly large capacity to learn and remember. Previous characterization of C. elegans genome and neuronal circuit makes this worm an ideal choice for studying behavior and the mechanisms that underlie it. Through careful behavioral and genetic studies, nematodes have been shown to form both short-term and long-term memory in associative and nonassociative training paradigms. Investigations of mechanosensory habituation and context-dependent learning in C. elegans have uncovered important similarities between learning in C. elegans and learning in vertebrates. These results include the discovery of common behavioral features in nonassociative learning between C. elegans and other organisms along with the identification of conserved genes that govern both nonassociative and associative learning. High-throughput studies have identified hundreds of genes implicated in memory and will potentially lead to insights into the fundamental strategies for encoding memory.
Author:
Publisher: Elsevier
ISBN: 0080478611
Category : Medical
Languages : en
Pages : 242
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Book Description
The Neurobiology of C. elegans assembles together a series of chapters describing the progress researchers have made toward solving some of the major problems in neurobiology with the use of this powerful model organism. The first chapter is an introduction to the anatomy of the C. elegans nervous system. This chapter provides a useful introduction to this system and will help the reader who is less familiar with this system understand the chapters that follow. The next two chapters on learning, conditioning and memory and neuronal specification and differentiation, summarize the current state of the C. elegans field in these two major areas of neurobiology. The remaining chapters describe studies in C. elegans that have provided particularly exciting insights into neurobiology.
Author: Katherine Kindt
Publisher:
ISBN:
Category :
Languages : en
Pages : 208
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Book Description
One of the main goals of neurobiology, and the focus of this dissertation, is to understand how genes act within a nervous system to generate behavior. The nematode Caenorhabditis elegans has a relatively simple nervous system comprised of 302 neurons with known connectivity. Despite this simplicity, C. elegans displays a wide-range of behaviors with surprising complexity. Well-developed genetics combined with a manageable nervous system make C. elegans a useful model to study how genes alter behavior. This dissertation focuses on the mechanosensory neurons of C. elegans. In the development of the gentle touch mechanosensory neurons, serotonin appears to act as permissive cue that allows these neurons to migrate to their proper locations. Mutations in Go-alpha (goa-1) signaling and the calcium channel (unc-2) also affect migration of the gentle touch neurons. Genetic analysis confirms that these genes act in the same pathway to confer motility to the migrating touch neurons. Dopamine is also important for the gentle touch neurons, but not developmentally. DOP-1, a D1-like dopamine receptor expressed in the touch neurons, is required for normal habituation of the gentle touch response. Cell-specific rescue confirms a role for DOP-1 signaling in the touch cells during habituation. Further genetic analysis indicates that Gq-alpha (egl-30) signaling couples to DOP-1. This signaling utilizes the second messengers IP3 and DAG to act on ER calcium and PKC activity respectively to modulate habituation. In vivo calcium imaging indicates that this signaling cascade acts cell autonomously to regulate touch cell sensitivity. Food is an essential cue for dopamine modulation of touch habituation; in the absence of food, DOP-1 worms habituate at the same rate as wildtype. Experiments also suggest that worms utilize their dopamine neurons to sense food mechanically, and release dopamine to slow habituation; this is dependent on the TRPN channel TRP-4. Another potential mechanosensitve TRP channel in C. elegans, TRPA-1 was recently identified. This channel is not required for gentle touch, but instead a distinct type of mechanosensation, nose touch and also foraging related behaviors. Cell-specific rescue and in vivo calcium imaging confirmed a direct role for TRPA-1 in nose touch neurons.
Author: John H. Byrne
Publisher: Oxford University Press
ISBN: 0190456787
Category : Science
Languages : en
Pages : 1304
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Book Description
Invertebrates have proven to be extremely useful model systems for gaining insights into the neural and molecular mechanisms of sensory processing, motor control and higher functions such as feeding behavior, learning and memory, navigation, and social behavior. A major factor in their enormous contributions to neuroscience is the relative simplicity of invertebrate nervous systems. In addition, some invertebrates, primarily the molluscs, have large cells, which allow analyses to take place at the level of individually identified neurons. Individual neurons can be surgically removed and assayed for expression of membrane channels, levels of second messengers, protein phosphorylation, and RNA and protein synthesis. Moreover, peptides and nucleotides can be injected into individual neurons. Other invertebrate model systems such as Drosophila and Caenorhabditis elegans offer tremendous advantages for obtaining insights into the neuronal bases of behavior through the application of genetic approaches. The Oxford Handbook of Invertebrate Neurobiology reviews the many neurobiological principles that have emerged from invertebrate analyses, such as motor pattern generation, mechanisms of synaptic transmission, and learning and memory. It also covers general features of the neurobiology of invertebrate circadian rhythms, development, and regeneration and reproduction. Some neurobiological phenomena are species-specific and diverse, especially in the domain of the neuronal control of locomotion and camouflage. Thus, separate chapters are provided on the control of swimming in annelids, crustaea and molluscs, locomotion in hexapods, and camouflage in cephalopods. Unique features of the handbook include chapters that review social behavior and intentionality in invertebrates. A chapter is devoted to summarizing past contributions of invertebrates to the understanding of nervous systems and identifying areas for future studies that will continue to advance that understanding.
Author: Randy F. Stout, Jr.
Publisher: Biota Publishing
ISBN: 1615046895
Category : Science
Languages : en
Pages : 66
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Book Description
The nematode C. elegans is one of the most important model organisms for understanding neurobiology. Its completely mapped neural connectome of 302 neurons and fully characterized and stereotyped development have made it a prototype for understanding nervous system structure, development, and function. Fifty-six out of C. elegans' total of 959 somatic cells are classified as neuroglia. Although research on worm glia has lagged behind studies focused on neurons, there has been a steep upswing in interest during the past decade. Information arising from the recent burst of research on worm glia supports the idea that C. elegans will continue to be an important animal model for understanding glial cell biology. Since the developmental lineage of all cells was mapped, each glial cell in C. elegans is known by a specific name and has research associated with it. We list and describe the glia of the hermaphrodite form of C. elegans and summarize research findings relating to each glial cell. We hope this lecture provides an informative overview of worm glia to accompany the excellent and freely available online resources available to the worm research community.
Author: Miloš Nikolić
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Seungwon Choi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Animals undergo periods of behavioral quiescence and arousal in response to environmental, circadian, or developmental cues. During larval molts, C. elegans undergoes a period of profound behavioral quiescence termed lethargus. Locomotion quiescence during lethargus was abolished in mutants lacking a neuropeptide receptor (NPR-1), and was reduced in mutants lacking NPR-1 ligands (FLP-18 and -21). Wild type strains are polymorphic for the npr-1 gene, and their lethargus behavior varies correspondingly. Locomotion quiescence and arousal were mediated by decreased and increased secretion of an arousal neuropeptide (PDF-1) from central neurons. PDF receptors (PDFR-1) expressed in peripheral mechanosensory neurons enhanced touch-evoked calcium transients. Thus, a central circuit stimulates arousal from lethargus by enhancing the sensitivity of peripheral mechanosensory neurons in the body. These results define a circuit mechanism controlling a developmentally programmed form of quiescence.
Author: Grigoriĭ Nikolaevich Orlovskiĭ
Publisher: Oxford Neuroscience
ISBN: 9780198524052
Category : Medical
Languages : en
Pages : 322
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Book Description
What does the swimming leech have to do with the running human? The ability to move actively in space is essential to members of the animal kingdom, and the evolution of the nervous system relates to a large extent to the evolution of locomotion. The extreme importance of locomotion hasstimulated many studies of the neural mechanisms underlying locomotion across a range of species. For the first time, a group of three leading neurobiologists have undertaken a comparative study of these mechanisms. Neuronal Control of Locomotion: From Mollusc to Man describes how the brains invery diverse and evolutionarily removed species control the animal's locomotion. In doing so, the authors reveal unifying principles of brain function, making it essential reading for students and researchers in neurobiology generally, and motor control in particular. "In my opinion, the authorshave produced a masterful and highly readable exposition on the neural control of locomotion. It is timely and relevant to avant- garde neuroscience. It will have a major impact on the field, and is sure to be referenced well into the second half of the next century." Douglas Stuart, Universityof Arizona College of Medicine
Author: Manon Guillermin
Publisher:
ISBN:
Category :
Languages : en
Pages : 97
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Adaptability is essential to organisms' fitness and survival. Evolutionary success depends on access to an array of behavioral choices in the face of changing environmental conditions. To navigate complex landscapes, organisms can interpret the significance of sensory stimuli, and assign context-appropriate valence, by integrating factors such as cues from their internal and external environments, and memories of previously experienced conditions, to dynamically shape neural circuits and generate ethologically relevant behaviors. In this thesis, I explore the cellular and molecular mechanisms that shape the carbon dioxide (CO2) circuit in the free-living nematode, Caenorhabditis elegans. CO2 is a complex sensory cue that can signify the presence of fruitful or dangerous surroundings. As a result, C. elegans can display a variety of different behaviors in response to CO2, from robust attraction to robust avoidance. Although sensory signaling of the CO2-responsive BAG neurons has been extensively characterized, how BAG communicates with postsynaptic interneurons, and how the CO2 signal is propagated through the nervous system to generate a context-appropriate behavior is unknown. First, we have found that neuromodulatory state and environmental oxygen (O2) levels converge on the CO2 circuit via the URX sensory neurons. The lab-derived N2 C. elegans strain expresses high levels of NPR-1 neuropeptide receptor, which inhibits URX and results in CO2 avoidance, regardless of environmental O2. In the C. elegans wild isolate "Hawaii", loss of npr-1 leads to modulation of URX by environmental O2, and results in CO2 avoidance at low O2, and loss of CO2-evoked behavior at high O2. Second, we present a new circuit motif that demonstrates how divergent responses to a single sensory input, CO2, can arise from an identical set of sensory and interneuron connections. We show that C. elegans exhibit an experience-dependent behavioral valence switch in response to CO2. While animals raised at ambient CO2 are repelled by CO2, animals raised in a high CO2 environment are attracted to CO2. Whether CO2 is attractive or repulsive is determined by the coordinated activity of specialized valence-encoding interneurons, AIY, RIG, and RIA, whose responses are subject to context-dependent modulation. An additional interneuron pair, AIZ, regulates behavioral sensitivity regardless of valence. Glutamatergic and neuropeptidergic signaling mediate both CO2 avoidance and attraction, and different neuropeptides play distinct roles in regulating valence and sensitivity. Our results elucidate a microcircuit motif whereby a fixed set of neurons are leveraged to generate alternative outputs in response to a single chemosensory input.
