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Abstract
AbstractMost rhythmic behaviors are produced by a specialized ensemble of neurons found in the central nervous system. These central pattern generators (CPGs) have become a cornerstone of neuronal circuit analysis. Studying simple invertebrate nervous systems may reveal the interactions of the neurons involved in the production of rhythmic motor output. There has recently been progress in this area, but due to certain intrinsic features of CPGs it is unlikely that present techniques will ever yield a complete understanding of any but the simplest of them. The chief impediment seems to be our inability to identify and characterize the total interneuronal pool making up a CPG. In addition, our general analytic strategy relies on a descriptive, reductionist approach, with no analytical constructs beyond phenomenological modeling. Detailed descriptive data are usually not of sufficient depth for specific model testing, giving rise instead to ad hoc explanations of mechanisms which usually turn out to be incorrect. Because they make too many assumptions, modeling studies have not added much to our understanding of CPCs; this is due not so much to inadequate simulations as to the poor quality and incomplete nature of the data provided by experimentalists.A basic strategy that would provide sufficient information for neural modeling would include: (1) identifying and characterizing each element in the CPG network; (2) specifying the synaptic connectivity between the elements; and (3) analyzing nonlinear synaptic properties and interactions by means of the connectivity matrix. Limitations based on our present technical capabilities are also discussed.
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The comparative approach to understanding central pattern generators. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Single-cell versus network properties and the use of models. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Adaptive significance, redundancy, and variance in central pattern generators. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Pessimism, models, and episodic behavior. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Do different behaviors require different central pattern generators. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Bursting networks. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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On neuronal nihilism. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Toward understanding central pattern generators. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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At what level will pattern generators be understood? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x0000683x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Particulars and principles of nervous activity. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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A practical approach to understanding central pattern generators. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Snake oil and the modeling process in neurobiology. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00006609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Newcomb JM, Fickbohm DJ, Katz PS. Comparative mapping of serotonin-immunoreactive neurons in the central nervous systems of nudibranch molluscs. J Comp Neurol 2006; 499:485-505. [PMID: 16998939 DOI: 10.1002/cne.21111] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The serotonergic systems in nudibranch molluscs were compared by mapping the locations of serotonin-immunoreactive (5-HT-ir) neurons in 11 species representing all four suborders of the nudibranch clade: Dendronotoidea (Tritonia diomedea, Tochuina tetraquetra, Dendronotus iris, Dendronotus frondosus, and Melibe leonina), Aeolidoidea (Hermissenda crassicornis and Flabellina trophina), Arminoidea (Dirona albolineata, Janolus fuscus, and Armina californica), and Doridoidea (Triopha catalinae). A nomenclature is proposed to standardize reports of cell location in species with differing brain morphologies. Certain patterns of 5-HT immunoreactivity were found to be consistent for all species, such as the presence of 5-HT-ir neurons in the pedal and cerebral ganglia. Also, particular clusters of 5-HT-ir neurons in the anterior and posterior regions of the dorsal surface of the cerebral ganglion were always present. However, there were interspecies differences in the number of 5-HT-ir neurons in each cluster, and some clusters even exhibited strong intraspecies variability that was only weakly correlated with brain size. Phylogenetic analysis suggests that the presence of particular classes of 5-HT-ir neurons exhibits a great deal of homoplasy. The conserved features of the nudibranch serotonergic system presumably represent the shared ancestral structure, whereas the derived characters suggest substantial independent evolutionary changes in the number and presence of serotonergic neurons. Although a number of studies have demonstrated phylogenetic variability of peptidergic systems, this study suggests that serotonergic systems may also exhibit a high degree of homoplasy in some groups of organisms.
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Affiliation(s)
- James M Newcomb
- Department of Biology, Georgia State University, Atlanta, Georgia 30303, USA.
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Janse C, van der Roest M, Slob W. Age-related decrease in electrical coupling of two identified neurons in the mollusc Lymnaea stagnalis. Brain Res 1986; 376:208-12. [PMID: 3719369 DOI: 10.1016/0006-8993(86)90920-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Electrophysiological characteristics of two identified giant electrotonically coupled neurosecretory cells in the central nervous system of the mollusc Lymnaea stagnalis were studied in mature animals of different age. The coupling coefficient of the neurons decreased considerably with age. The possibility that the decrease is due to an increase in the junctional resistance between the cells is discussed.
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Dagan D, Adams WB. Triplicated bursting neuron R15 in an Aplysia abdominal ganglion: non-symmetrical coupling, common synaptic inputs and response to dopamine. Brain Res 1981; 208:59-65. [PMID: 6258749 DOI: 10.1016/0006-8993(81)90620-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
An abdominal ganglion of the mollusc Aplysia californica was found to contain 3 neurons in the place normally occupied by a single R15 cell. The 3 neurons exhibited properties characteristic of R15 neurons including spontaneous bursts. The bursts appeared asynchronously in spite of electrotonic coupling between them. The coupling function approximated a low pass filter with a cut-off frequency between 0.02 and 0.05 Hz in accordance with a measured coupling time-constant of 5--10 sec. Coupling measured in the cell body was found to be stronger for hyperpolarizing currents than for depolarizing currents injected into any of the 3 cells. This 'symmetrical rectification' can be explained by a rectifying axonal membrane interposed between the site of coupling and the site of recording. All 3 cells were found to have dopamine receptors and to receive common synaptic inputs. Since the coupling efficiency was found to vary depending on the direction of current flow, depolarizing synaptic inputs and spike burst generation remain autonomous.
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van Swigchem H. Electrotonic coupling within a cluster of neurosecretory endogenous oscillators in Lymnaea stagnalis (L.). ACTA ACUST UNITED AC 1981. [DOI: 10.1016/0300-9629(81)90341-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Philosophy leads to pessimism, research to understanding. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Central pattern generator analysis is alive and well. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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A new generation of experimental and theoretical methods is needed in neuroblology. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Models, modelling, and the leech swimming rhythm. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x0000666x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Graded transmission, mechanistic multiplicity, and modeling. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Central pattern generators can be understood. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Central pattern generators and sensory input. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Expectation and achievement in analysis of motor program generation. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Models and multineuron recordings. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Neuroethological analysis of central pattern generators. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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The failure of current strategies in the study of central pattern generators. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Central pattern generators (CPGs) from the viewpoint of a behavioral physiologist. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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The implications of recent experimental results for the validity of modeling studies of the leech swim central pattern generator. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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On the history and value of the central pattern generator concept. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Roles for models in understanding neural networks. Behav Brain Sci 1980. [DOI: 10.1017/s0140525x00006737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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