51
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Ofer N, Shefi O, Yaari G. Branching morphology determines signal propagation dynamics in neurons. Sci Rep 2017; 7:8877. [PMID: 28827727 PMCID: PMC5567046 DOI: 10.1038/s41598-017-09184-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 07/24/2017] [Indexed: 11/09/2022] Open
Abstract
Computational modeling of signal propagation in neurons is critical to our understanding of basic principles underlying brain organization and activity. Exploring these models is used to address basic neuroscience questions as well as to gain insights for clinical applications. The seminal Hodgkin Huxley model is a common theoretical framework to study brain activity. It was mainly used to investigate the electrochemical and physical properties of neurons. The influence of neuronal structure on activity patterns was explored, however, the rich dynamics observed in neurons with different morphologies is not yet fully understood. Here, we study signal propagation in fundamental building blocks of neuronal branching trees, unbranched and branched axons. We show how these simple axonal elements can code information on spike trains, and how asymmetric responses can emerge in axonal branching points. This asymmetric phenomenon has been observed experimentally but until now lacked theoretical characterization. Together, our results suggest that axonal morphological parameters are instrumental in activity modulation and information coding. The insights gained from this work lay the ground for better understanding the interplay between function and form in real-world complex systems. It may also supply theoretical basis for the development of novel therapeutic approaches to damaged nervous systems.
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Affiliation(s)
- Netanel Ofer
- Faculty of Engineering, Bar Ilan University, Ramat Gan, 5290002, Israel.,Bar Ilan Institute of Nanotechnologies and Advanced Materials, Bar Ilan University, Ramat Gan, 5290002, Israel
| | - Orit Shefi
- Faculty of Engineering, Bar Ilan University, Ramat Gan, 5290002, Israel. .,Bar Ilan Institute of Nanotechnologies and Advanced Materials, Bar Ilan University, Ramat Gan, 5290002, Israel.
| | - Gur Yaari
- Faculty of Engineering, Bar Ilan University, Ramat Gan, 5290002, Israel.
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52
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Papoutsi A, Kastellakis G, Poirazi P. Basal tree complexity shapes functional pathways in the prefrontal cortex. J Neurophysiol 2017; 118:1970-1983. [PMID: 28701532 DOI: 10.1152/jn.00099.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 06/29/2017] [Accepted: 07/07/2017] [Indexed: 11/22/2022] Open
Abstract
While the morphology of basal dendritic trees in cortical pyramidal neurons varies, the functional implications of this diversity are just starting to emerge. In layer 5 pyramidal neurons of the prefrontal cortex, for example, increased basal tree complexity determines the recruitment of these neurons into functional circuits. Here, we use a modeling approach to investigate whether and how the morphology of the basal tree mediates the functional output of neurons. We implemented 57 basal tree morphologies of layer 5 prefrontal pyramidal neurons of the rat and identified morphological types that were characterized by different response features, forming distinct functional types. These types were robust to a wide range of manipulations (distribution of active ionic mechanisms, NMDA conductance, somatic and apical tree morphology, or the number of activated synapses) and supported different temporal coding schemes at both the single neuron and the microcircuit level. We predict that the basal tree morphological diversity among neurons of the same class mediates their segregation into distinct functional pathways. Extension of our approach/findings to other cortical areas and/or layers or under pathological conditions may provide a generalized role of the basal trees for neuronal function.NEW & NOTEWORTHY Our results suggest that the segregation of neurons to different functional types based on their basal tree morphology is in large part independent of the distribution of active ionic mechanisms, NMDA conductance, somatic and apical tree morphology, and the number of activated synapses; different functional types support distinct temporal coding schemes. This can be exploited to create networks with diverse coding characteristics, thus contributing to the functional heterogeneity within the same layer and area.
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Affiliation(s)
- Athanasia Papoutsi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece; and
| | - George Kastellakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece; and.,Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete, Greece; and
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53
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Vormberg A, Effenberger F, Muellerleile J, Cuntz H. Universal features of dendrites through centripetal branch ordering. PLoS Comput Biol 2017; 13:e1005615. [PMID: 28671947 PMCID: PMC5515450 DOI: 10.1371/journal.pcbi.1005615] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 07/18/2017] [Accepted: 06/05/2017] [Indexed: 11/19/2022] Open
Abstract
Dendrites form predominantly binary trees that are exquisitely embedded in the networks of the brain. While neuronal computation is known to depend on the morphology of dendrites, their underlying topological blueprint remains unknown. Here, we used a centripetal branch ordering scheme originally developed to describe river networks—the Horton-Strahler order (SO)–to examine hierarchical relationships of branching statistics in reconstructed and model dendritic trees. We report on a number of universal topological relationships with SO that are true for all binary trees and distinguish those from SO-sorted metric measures that appear to be cell type-specific. The latter are therefore potential new candidates for categorising dendritic tree structures. Interestingly, we find a faithful correlation of branch diameters with centripetal branch orders, indicating a possible functional importance of SO for dendritic morphology and growth. Also, simulated local voltage responses to synaptic inputs are strongly correlated with SO. In summary, our study identifies important SO-dependent measures in dendritic morphology that are relevant for neural function while at the same time it describes other relationships that are universal for all dendrites. Similarly to river beds, dendritic trees of nerve cells form elaborate networks that branch out to cover extensive areas. In the 1940s, ecologist Robert E. Horton developed an ordering system for branches in river networks that was refined in the 1950s by geoscientist Arthur N. Strahler, the Horton-Strahler order (SO). Branches at the tips start with order 1 and increase their order in a systematic way when encountering new branches on the way to the root. SO relationships have recently become popular for quantifying dendritic morphologies. Various branching statistics can be studied as a function of SO. Here we describe that topological measures such as the number of branches, the branch bifurcation ratio and the size of subtrees exhibit stereotypical relations with SO in dendritic trees independently of cell type, mirroring universal features of binary trees. Other functionally more relevant features such as mean branch lengths, local diameters and simulated voltage responses to synaptic inputs directly correlate with SO in a cell type-specific manner, indicating the importance of SO for understanding dendrite growth as well as neural computation.
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Affiliation(s)
- Alexandra Vormberg
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, Frankfurt/Main, Germany
- Frankfurt Institute for Advanced Studies (FIAS), Frankfurt/Main, Germany
- * E-mail: (A.V.); (H.C.)
| | - Felix Effenberger
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, Frankfurt/Main, Germany
- Frankfurt Institute for Advanced Studies (FIAS), Frankfurt/Main, Germany
| | - Julia Muellerleile
- Institute of Clinical Neuroanatomy, Goethe University Frankfurt/Main, Germany
| | - Hermann Cuntz
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, Frankfurt/Main, Germany
- Frankfurt Institute for Advanced Studies (FIAS), Frankfurt/Main, Germany
- * E-mail: (A.V.); (H.C.)
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54
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Almog M, Korngreen A. Is realistic neuronal modeling realistic? J Neurophysiol 2016; 116:2180-2209. [PMID: 27535372 DOI: 10.1152/jn.00360.2016] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/17/2016] [Indexed: 11/22/2022] Open
Abstract
Scientific models are abstractions that aim to explain natural phenomena. A successful model shows how a complex phenomenon arises from relatively simple principles while preserving major physical or biological rules and predicting novel experiments. A model should not be a facsimile of reality; it is an aid for understanding it. Contrary to this basic premise, with the 21st century has come a surge in computational efforts to model biological processes in great detail. Here we discuss the oxymoronic, realistic modeling of single neurons. This rapidly advancing field is driven by the discovery that some neurons don't merely sum their inputs and fire if the sum exceeds some threshold. Thus researchers have asked what are the computational abilities of single neurons and attempted to give answers using realistic models. We briefly review the state of the art of compartmental modeling highlighting recent progress and intrinsic flaws. We then attempt to address two fundamental questions. Practically, can we realistically model single neurons? Philosophically, should we realistically model single neurons? We use layer 5 neocortical pyramidal neurons as a test case to examine these issues. We subject three publically available models of layer 5 pyramidal neurons to three simple computational challenges. Based on their performance and a partial survey of published models, we conclude that current compartmental models are ad hoc, unrealistic models functioning poorly once they are stretched beyond the specific problems for which they were designed. We then attempt to plot possible paths for generating realistic single neuron models.
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Affiliation(s)
- Mara Almog
- The Leslie and Susan Gonda Interdisciplinary Brain Research Centre, Bar-Ilan University, Ramat Gan, Israel; and.,The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Alon Korngreen
- The Leslie and Susan Gonda Interdisciplinary Brain Research Centre, Bar-Ilan University, Ramat Gan, Israel; and .,The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
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55
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Chen LJ, Wang YJ, Chen JR, Tseng GF. Hydrocephalus compacted cortex and hippocampus and altered their output neurons in association with spatial learning and memory deficits in rats. Brain Pathol 2016; 27:419-436. [PMID: 27411167 DOI: 10.1111/bpa.12414] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 07/04/2016] [Indexed: 12/29/2022] Open
Abstract
Hydrocephalus is a common neurological disorder in children characterized by abnormal dilation of cerebral ventricles as a result of the impairment of cerebrospinal fluid flow or absorption. Clinical presentation of hydrocephalus varies with chronicity and often shows cognitive dysfunction. Here we used a kaolin-induction method in rats and studied the effects of hydrocephalus on cerebral cortex and hippocampus, the two regions highly related to cognition. Hydrocephalus impaired rats' performance in Morris water maze task. Serial three-dimensional reconstruction from sections of the whole brain freshly froze in situ with skull shows that the volumes of both structures were reduced. Morphologically, pyramidal neurons of the somatosensory cortex and hippocampus appear to be distorted. Intracellular dye injection and subsequent three-dimensional reconstruction and analyses revealed that the dendritic arbors of layer III and V cortical pyramid neurons were reduced. The total dendritic length of CA1, but not CA3, pyramidal neurons was also reduced. Dendritic spine densities on both cortical and hippocampal pyramidal neurons were decreased, consistent with our concomitant findings that the expressions of both synaptophysin and postsynaptic density protein 95 were reduced. These cortical and hippocampal changes suggest reductions of excitatory connectivity, which could underlie the learning and memory deficits in hydrocephalus.
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Affiliation(s)
- Li-Jin Chen
- Department of Anatomy, College of Medicine, Tzu-Chi University, Hualien City, Taiwan
| | - Yueh-Jan Wang
- Department of Anatomy, College of Medicine, Tzu-Chi University, Hualien City, Taiwan
| | - Jeng-Rung Chen
- Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan
| | - Guo-Fang Tseng
- Department of Anatomy, College of Medicine, Tzu-Chi University, Hualien City, Taiwan
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56
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Zhu G, Du L, Jin L, Offenhäusser A. Effects of Morphology Constraint on Electrophysiological Properties of Cortical Neurons. Sci Rep 2016; 6:23086. [PMID: 27052791 PMCID: PMC4823731 DOI: 10.1038/srep23086] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/26/2016] [Indexed: 11/08/2022] Open
Abstract
There is growing interest in engineering nerve cells in vitro to control architecture and connectivity of cultured neuronal networks or to build neuronal networks with predictable computational function. Pattern technologies, such as micro-contact printing, have been developed to design ordered neuronal networks. However, electrophysiological characteristics of the single patterned neuron haven't been reported. Here, micro-contact printing, using polyolefine polymer (POP) stamps with high resolution, was employed to grow cortical neurons in a designed structure. The results demonstrated that the morphology of patterned neurons was well constrained, and the number of dendrites was decreased to be about 2. Our electrophysiological results showed that alterations of dendritic morphology affected firing patterns of neurons and neural excitability. When stimulated by current, though both patterned and un-patterned neurons presented regular spiking, the dynamics and strength of the response were different. The un-patterned neurons exhibited a monotonically increasing firing frequency in response to injected current, while the patterned neurons first exhibited frequency increase and then a slow decrease. Our findings indicate that the decrease in dendritic complexity of cortical neurons will influence their electrophysiological characteristics and alter their information processing activity, which could be considered when designing neuronal circuitries.
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Affiliation(s)
- Geng Zhu
- Institute of Complex Systems, Bioelectronics (PGI-8/ICS-8), Forschungszentrum Jülich, JARA – FIT, Jülich D-52425, Germany
- Bio-X Institutes, Key Laboratory for the Genetics of Development and Neuropsychiatric Disorders (Ministry of Education), and Shanghai Key Laboratory of Psychotic Disorders, Brain Science and Technology Research Center, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Liping Du
- Institute of Complex Systems, Bioelectronics (PGI-8/ICS-8), Forschungszentrum Jülich, JARA – FIT, Jülich D-52425, Germany
- Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China
| | - Lei Jin
- Institute of Complex Systems, Bioelectronics (PGI-8/ICS-8), Forschungszentrum Jülich, JARA – FIT, Jülich D-52425, Germany
| | - Andreas Offenhäusser
- Institute of Complex Systems, Bioelectronics (PGI-8/ICS-8), Forschungszentrum Jülich, JARA – FIT, Jülich D-52425, Germany
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57
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Mellström B, Kastanauskaite A, Knafo S, Gonzalez P, Dopazo XM, Ruiz-Nuño A, Jefferys JGR, Zhuo M, Bliss TVP, Naranjo JR, DeFelipe J. Specific cytoarchitectureal changes in hippocampal subareas in daDREAM mice. Mol Brain 2016; 9:22. [PMID: 26928278 PMCID: PMC4772309 DOI: 10.1186/s13041-016-0204-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 02/22/2016] [Indexed: 11/20/2022] Open
Abstract
Background Transcriptional repressor DREAM (downstream regulatory element antagonist modulator) is a Ca2+-binding protein that regulates Ca2+ homeostasis through gene regulation and protein-protein interactions. It has been shown that a dominant active form (daDREAM) is implicated in learning-related synaptic plasticity such as LTP and LTD in the hippocampus. Neuronal spines are reported to play important roles in plasticity and memory. However, the possible role of DREAM in spine plasticity has not been reported. Results Here we show that potentiating DREAM activity, by overexpressing daDREAM, reduced dendritic basal arborization and spine density in CA1 pyramidal neurons and increased spine density in dendrites in dentate gyrus granule cells. These microanatomical changes are accompanied by significant modifications in the expression of specific genes encoding the cytoskeletal proteins Arc, Formin 1 and Gelsolin in daDREAM hippocampus. Conclusions Our results strongly suggest that DREAM plays an important role in structural plasticity in the hippocampus. Electronic supplementary material The online version of this article (doi:10.1186/s13041-016-0204-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Britt Mellström
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,National Biotechnology Center. CSIC, Darwin, 3. E-28049, Madrid, Spain.
| | - Asta Kastanauskaite
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,Cajal Institute, CSIC Madrid, Av Dr. Arce,37 E-28006, Madrid, Spain. .,Biomedical Technology Center, Politecnica University Madrid, Madrid, Spain.
| | - Shira Knafo
- Cajal Institute, CSIC Madrid, Av Dr. Arce,37 E-28006, Madrid, Spain. .,Present address: IkerBasque Basque Foundation for Science and BioCruces, Health Research Institute, Bizkaia, Spain.
| | - Paz Gonzalez
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,National Biotechnology Center. CSIC, Darwin, 3. E-28049, Madrid, Spain.
| | - Xose M Dopazo
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,National Biotechnology Center. CSIC, Darwin, 3. E-28049, Madrid, Spain.
| | - Ana Ruiz-Nuño
- Neuronal Networks Group, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK.
| | - John G R Jefferys
- Neuronal Networks Group, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK.
| | - Min Zhuo
- Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada. .,Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
| | - Tim V P Bliss
- MRC National Institutes for Medical Research, Mill Hill, London, UK.
| | - Jose R Naranjo
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,National Biotechnology Center. CSIC, Darwin, 3. E-28049, Madrid, Spain.
| | - Javier DeFelipe
- Spanish Network for Biomedical Research in Neurodegenerative Diseases, CIBERNED, Madrid, Spain. .,Cajal Institute, CSIC Madrid, Av Dr. Arce,37 E-28006, Madrid, Spain. .,Biomedical Technology Center, Politecnica University Madrid, Madrid, Spain.
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58
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Platschek S, Cuntz H, Vuksic M, Deller T, Jedlicka P. A general homeostatic principle following lesion induced dendritic remodeling. Acta Neuropathol Commun 2016; 4:19. [PMID: 26916562 PMCID: PMC4766619 DOI: 10.1186/s40478-016-0285-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 02/06/2016] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION Neuronal death and subsequent denervation of target areas are hallmarks of many neurological disorders. Denervated neurons lose part of their dendritic tree, and are considered "atrophic", i.e. pathologically altered and damaged. The functional consequences of this phenomenon are poorly understood. RESULTS Using computational modelling of 3D-reconstructed granule cells we show that denervation-induced dendritic atrophy also subserves homeostatic functions: By shortening their dendritic tree, granule cells compensate for the loss of inputs by a precise adjustment of excitability. As a consequence, surviving afferents are able to activate the cells, thereby allowing information to flow again through the denervated area. In addition, action potentials backpropagating from the soma to the synapses are enhanced specifically in reorganized portions of the dendritic arbor, resulting in their increased synaptic plasticity. These two observations generalize to any given dendritic tree undergoing structural changes. CONCLUSIONS Structural homeostatic plasticity, i.e. homeostatic dendritic remodeling, is operating in long-term denervated neurons to achieve functional homeostasis.
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59
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Neuron Morphology Influences Axon Initial Segment Plasticity. eNeuro 2016; 3:eN-NWR-0085-15. [PMID: 27022619 PMCID: PMC4756267 DOI: 10.1523/eneuro.0085-15.2016] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 12/11/2015] [Accepted: 01/14/2016] [Indexed: 11/21/2022] Open
Abstract
In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation.
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60
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Rojo C, Leguey I, Kastanauskaite A, Bielza C, Larrañaga P, DeFelipe J, Benavides-Piccione R. Laminar Differences in Dendritic Structure of Pyramidal Neurons in the Juvenile Rat Somatosensory Cortex. Cereb Cortex 2016; 26:2811-2822. [PMID: 26762857 PMCID: PMC4869814 DOI: 10.1093/cercor/bhv316] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Pyramidal cell structure varies between different cortical areas and species, indicating that the cortical circuits that these cells participate in are likely to be characterized by different functional capabilities. Structural differences between cortical layers have been traditionally reported using either the Golgi method or intracellular labeling, but the structure of pyramidal cells has not previously been systematically analyzed across all cortical layers at a particular age. In the present study, we investigated the dendritic architecture of complete basal arbors of pyramidal neurons in layers II, III, IV, Va, Vb, and VI of the hindlimb somatosensory cortical region of postnatal day 14 rats. We found that the characteristics of basal dendritic morphologies are statistically different in each cortical layer. The variations in size and branching pattern that exist between pyramidal cells of different cortical layers probably reflect the particular functional properties that are characteristic of the cortical circuit in which they participate. This new set of complete basal dendritic arbors of 3D-reconstructed pyramidal cell morphologies across each cortical layer will provide new insights into interlaminar information processing in the cerebral cortex.
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Affiliation(s)
- Concepción Rojo
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica.,Departamento de Anatomía y Anatomía Patológica Comparada, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain
| | - Ignacio Leguey
- Departamento de Inteligencia Artificial, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid, Madrid, Spain
| | - Asta Kastanauskaite
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Concha Bielza
- Departamento de Inteligencia Artificial, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid, Madrid, Spain
| | - Pedro Larrañaga
- Departamento de Inteligencia Artificial, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid, Madrid, Spain
| | - Javier DeFelipe
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica.,Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Ruth Benavides-Piccione
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica.,Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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61
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Targeted pruning of a neuron's dendritic tree via femtosecond laser dendrotomy. Sci Rep 2016; 6:19078. [PMID: 26739126 PMCID: PMC4703956 DOI: 10.1038/srep19078] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/04/2015] [Indexed: 12/25/2022] Open
Abstract
Neurons are classified according to action potential firing in response to current injection. While such firing patterns are shaped by the composition and distribution of ion channels, modelling studies suggest that the geometry of dendritic branches also influences temporal firing patterns. Verifying this link is crucial to understanding how neurons transform their inputs to output but has so far been technically challenging. Here, we investigate branching-dependent firing by pruning the dendritic tree of pyramidal neurons. We use a focused ultrafast laser to achieve highly localized and minimally invasive cutting of dendrites, thus keeping the rest of the dendritic tree intact and the neuron functional. We verify successful dendrotomy via two-photon uncaging of neurotransmitters before and after dendrotomy at sites around the cut region and via biocytin staining. Our results show that significantly altering the dendritic arborisation, such as by severing the apical trunk, enhances excitability in layer V cortical pyramidal neurons as predicted by simulations. This method may be applied to the analysis of specific relationships between dendritic structure and neuronal function. The capacity to dynamically manipulate dendritic topology or isolate inputs from various dendritic domains can provide a fresh perspective on the roles they play in shaping neuronal output.
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62
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Kim H, Heckman CJ. Foundational dendritic processing that is independent of the cell type-specific structure in model primary neurons. Neurosci Lett 2015; 609:203-9. [PMID: 26463670 PMCID: PMC4679609 DOI: 10.1016/j.neulet.2015.10.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 10/04/2015] [Accepted: 10/05/2015] [Indexed: 11/16/2022]
Abstract
It has long been known that primary neurons in the brain and spinal cord exhibit very distinctive dendritic structures. However, it remains unclear whether dendritic processing for signal propagation and channel activation over dendrites is a function of the cell type-specific dendritic structure. By applying an extended analysis of signal attenuation for the physiological distributions of synaptic inputs and active channels on dendritic branches, we first demonstrate that regardless of their specific structure, all anatomically reconstructed models of primary neurons display a similar pattern of directional signal attenuation and locational channel activation over their dendrites. Then, using a novel modeling approach that allows direct comparison of the anatomically reconstructed primary neurons with their reduced models that exclusively retain anatomical dendritic signaling without being associated with structural specificity, we show that the reduced model can accurately predict dendritic excitability of the anatomical model in both passive and active mode. These results indicate that the directional signaling, locational excitability and their relationship are foundational features of dendritic processing that are independent of the cell type-specific structure across primary neurons.
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Affiliation(s)
- Hojeong Kim
- Division of IoT·Robotics Convergence Research, DGIST, 50-1, Sang, Hyeonpung, Dalseong, Daegu, Gyeongbuk 711-873, Republic of Korea; Department of Physiology, Northwestern University of Medicine, Chicago, USA.
| | - C J Heckman
- Department of Physiology, Northwestern University of Medicine, Chicago, USA; Department of Physical Medicine and Rehabilitation, and Physical Therapy and Human Movement Science, Northwestern University Feinberg School of Medicine, Chicago, USA
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63
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Farrell MR, Gruene TM, Shansky RM. The influence of stress and gonadal hormones on neuronal structure and function. Horm Behav 2015; 76:118-24. [PMID: 25819727 PMCID: PMC4583315 DOI: 10.1016/j.yhbeh.2015.03.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 03/11/2015] [Accepted: 03/19/2015] [Indexed: 11/27/2022]
Abstract
This article is part of a Special Issue "SBN 2014". The brain is highly plastic, allowing us to adapt and respond to environmental and physiological challenges and experiences. In this review, we discuss the relationships among alterations in dendritic arborization, spine morphology, and behavior due to stress exposure, endogenous hormone fluctuation, or exogenous hormonal manipulation. Very few studies investigate structure-function associations directly in the same cohort of animals, and there are notable inconsistencies in evidence of structure-function relationships in the prefrontal cortex and hippocampus. Moreover, little work has been done to probe the causal relationship between dendritic morphology and neuronal excitability, leaving only speculation about the adaptive versus maladaptive nature of experience-dependent dendritic remodeling. We propose that future studies combine electrophysiology with a circuit-level approach to better understand how dendritic structure contributes to neuronal functional properties and behavioral outcomes.
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Affiliation(s)
| | - Tina M Gruene
- Department of Psychology, Northeastern University, USA
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64
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Yuan TF, Peng B, Machado S, Arias-Carrion O. Morphological Bases of Neuronal Hyperexcitability in Neurodegeneration. CNS Neurosci Ther 2015; 21:867-9. [PMID: 26494127 DOI: 10.1111/cns.12439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Ti-Fei Yuan
- School of psychology, Nanjing Normal university, Nanjing, China
| | - Bo Peng
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Sergio Machado
- Panic and Respiration, Institute of Psychiatry of Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Oscar Arias-Carrion
- Unidad de Trastornos del Movimiento y Sueño (TMS), Hospital General Dr. Manuel Gea González/IFC-UNAM, Mexico City, Mexico
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65
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Abstract
The nervous system is populated by numerous types of neurons, each bearing a dendritic arbor with a characteristic morphology. These type-specific features influence many aspects of a neuron's function, including the number and identity of presynaptic inputs and how inputs are integrated to determine firing properties. Here, we review the mechanisms that regulate the construction of cell type-specific dendrite patterns during development. We focus on four aspects of dendrite patterning that are particularly important in determining the function of the mature neuron: (a) dendrite shape, including branching pattern and geometry of the arbor; (b) dendritic arbor size;
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Affiliation(s)
| | - Joshua R Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138;
| | - Jeremy N Kay
- Departments of Neurobiology and Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27710;
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66
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de Wiljes OO, van Elburg RAJ, Biehl M, Keijzer FA. Modeling spontaneous activity across an excitable epithelium: Support for a coordination scenario of early neural evolution. Front Comput Neurosci 2015; 9:110. [PMID: 26441620 PMCID: PMC4569742 DOI: 10.3389/fncom.2015.00110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 08/24/2015] [Indexed: 11/24/2022] Open
Abstract
Internal coordination models hold that early nervous systems evolved in the first place to coordinate internal activity at a multicellular level, most notably the use of multicellular contractility as an effector for motility. A recent example of such a model, the skin brain thesis, suggests that excitable epithelia using chemical signaling are a potential candidate as a nervous system precursor. We developed a computational model and a measure for whole body coordination to investigate the coordinative properties of such excitable epithelia. Using this measure we show that excitable epithelia can spontaneously exhibit body-scale patterns of activation. Relevant factors determining the extent of patterning are the noise level for exocytosis, relative body dimensions, and body size. In smaller bodies whole-body coordination emerges from cellular excitability and bidirectional excitatory transmission alone. Our results show that basic internal coordination as proposed by the skin brain thesis could have arisen in this potential nervous system precursor, supporting that this configuration may have played a role as a proto-neural system and requires further investigation.
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Affiliation(s)
- Oltman O. de Wiljes
- Department of Theoretical Philosophy, Faculty of Philosophy, University of GroningenGroningen, Netherlands
- Faculty of Mathematics and Natural Sciences, Institute of Artificial Intelligence, University of GroningenGroningen, Netherlands
| | - Ronald A. J. van Elburg
- Faculty of Mathematics and Natural Sciences, Institute of Artificial Intelligence, University of GroningenGroningen, Netherlands
| | - Michael Biehl
- Faculty of Mathematics and Natural Sciences, Johann Bernoulli Institute for Mathematics and Computer Science, University of GroningenGroningen, Netherlands
| | - Fred A. Keijzer
- Department of Theoretical Philosophy, Faculty of Philosophy, University of GroningenGroningen, Netherlands
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67
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Singh MF, Zald DH. A simple transfer function for nonlinear dendritic integration. Front Comput Neurosci 2015; 9:98. [PMID: 26321940 PMCID: PMC4530314 DOI: 10.3389/fncom.2015.00098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 07/15/2015] [Indexed: 11/13/2022] Open
Abstract
Relatively recent advances in patch clamp recordings and iontophoresis have enabled unprecedented study of neuronal post-synaptic integration ("dendritic integration"). Findings support a separate layer of integration in the dendritic branches before potentials reach the cell's soma. While integration between branches obeys previous linear assumptions, proximal inputs within a branch produce threshold nonlinearity, which some authors have likened to the sigmoid function. Here we show the implausibility of a sigmoidal relation and present a more realistic transfer function in both an elegant artificial form and a biophysically derived form that further considers input locations along the dendritic arbor. As the distance between input locations determines their ability to produce nonlinear interactions, models incorporating dendritic topology are essential to understanding the computational power afforded by these early stages of integration. We use the biophysical transfer function to emulate empirical data using biophysical parameters and describe the conditions under which the artificial and biophysically derived forms are equivalent.
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Affiliation(s)
- Matthew F Singh
- Department of Psychology, Vanderbilt University Nashville, TN, USA ; Department of Psychiatry, Vanderbilt University Nashville, TN, USA
| | - David H Zald
- Department of Psychology, Vanderbilt University Nashville, TN, USA ; The Program in Neurosciences, Washington University School of Medicine in St. Louis St. Louis, MO, USA
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68
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Mohan H, Verhoog MB, Doreswamy KK, Eyal G, Aardse R, Lodder BN, Goriounova NA, Asamoah B, B Brakspear ABC, Groot C, van der Sluis S, Testa-Silva G, Obermayer J, Boudewijns ZSRM, Narayanan RT, Baayen JC, Segev I, Mansvelder HD, de Kock CPJ. Dendritic and Axonal Architecture of Individual Pyramidal Neurons across Layers of Adult Human Neocortex. Cereb Cortex 2015; 25:4839-53. [PMID: 26318661 PMCID: PMC4635923 DOI: 10.1093/cercor/bhv188] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The size and shape of dendrites and axons are strong determinants of neuronal information processing. Our knowledge on neuronal structure and function is primarily based on brains of laboratory animals. Whether it translates to human is not known since quantitative data on "full" human neuronal morphologies are lacking. Here, we obtained human brain tissue during resection surgery and reconstructed basal and apical dendrites and axons of individual neurons across all cortical layers in temporal cortex (Brodmann area 21). Importantly, morphologies did not correlate to etiology, disease severity, or disease duration. Next, we show that human L(ayer) 2 and L3 pyramidal neurons have 3-fold larger dendritic length and increased branch complexity with longer segments compared with temporal cortex neurons from macaque and mouse. Unsupervised cluster analysis classified 88% of human L2 and L3 neurons into human-specific clusters distinct from mouse and macaque neurons. Computational modeling of passive electrical properties to assess the functional impact of large dendrites indicates stronger signal attenuation of electrical inputs compared with mouse. We thus provide a quantitative analysis of "full" human neuron morphologies and present direct evidence that human neurons are not "scaled-up" versions of rodent or macaque neurons, but have unique structural and functional properties.
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Affiliation(s)
- Hemanth Mohan
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Matthijs B Verhoog
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Keerthi K Doreswamy
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Guy Eyal
- Department of Neurobiology and Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Romy Aardse
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Brendan N Lodder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Natalia A Goriounova
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Boateng Asamoah
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - A B Clementine B Brakspear
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Colin Groot
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Sophie van der Sluis
- Department of Clinical Genetics, Section Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, VU Medical Center, Amsterdam, The Netherlands
| | - Guilherme Testa-Silva
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Joshua Obermayer
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Zimbo S R M Boudewijns
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Rajeevan T Narayanan
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Johannes C Baayen
- Department of Neurosurgery, VU University Medical Center, Amsterdam 1081 HV, The Netherlands
| | - Idan Segev
- Department of Neurobiology and Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Huibert D Mansvelder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
| | - Christiaan P J de Kock
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands
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69
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Altered sensory processing and dendritic remodeling in hyperexcitable visual cortical networks. Brain Struct Funct 2015; 221:2919-36. [PMID: 26163822 DOI: 10.1007/s00429-015-1080-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 07/01/2015] [Indexed: 01/20/2023]
Abstract
Epilepsy is characterized by impaired circuit function and a propensity for spontaneous seizures, but how plastic rearrangements within the epileptic focus trigger cortical dysfunction and hyperexcitability is only partly understood. Here we have examined alterations in sensory processing and the underlying biochemical and neuroanatomical changes in tetanus neurotoxin (TeNT)-induced focal epilepsy in mouse visual cortex. We documented persistent epileptiform electrographic discharges and upregulation of GABAergic markers at the completion of TeNT effects. We also found a significant remodeling of the dendritic arbors of pyramidal neurons, with increased dendritic length and branching, and overall reduction in spine density but significant preservation of mushroom, mature spines. Functionally, spontaneous neuronal discharge was increased, visual responses were less reliable, and electrophysiological and behavioural visual acuity was consistently impaired in TeNT-injected mice. These data demonstrate robust, long-term remodeling of both inhibitory and excitatory circuitry associated with specific disturbances of network function in neocortical epilepsy.
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70
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Abstract
An open question within the Bienenstock-Cooper-Munro theory for synaptic modification concerns the specific mechanism that is responsible for regulating the sliding modification threshold (SMT). In this conductance-based modeling study on hippocampal pyramidal neurons, we quantitatively assessed the impact of seven ion channels (R- and T-type calcium, fast sodium, delayed rectifier, A-type, and small-conductance calcium-activated (SK) potassium and HCN) and two receptors (AMPAR and NMDAR) on a calcium-dependent Bienenstock-Cooper-Munro-like plasticity rule. Our analysis with R- and T-type calcium channels revealed that differences in their activation-inactivation profiles resulted in differential impacts on how they altered the SMT. Further, we found that the impact of SK channels on the SMT critically depended on the voltage dependence and kinetics of the calcium sources with which they interacted. Next, we considered interactions among all the seven channels and the two receptors through global sensitivity analysis on 11 model parameters. We constructed 20,000 models through uniform randomization of these parameters and found 360 valid models based on experimental constraints on their plasticity profiles. Analyzing these 360 models, we found that similar plasticity profiles could emerge with several nonunique parametric combinations and that parameters exhibited weak pairwise correlations. Finally, we used seven sets of virtual knock-outs on these 360 models and found that the impact of different channels on the SMT was variable and differential. These results suggest that there are several nonunique routes to regulate the SMT, and call for a systematic analysis of the variability and state dependence of the mechanisms underlying metaplasticity during behavior and pathology.
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71
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Coskren PJ, Luebke JI, Kabaso D, Wearne SL, Yadav A, Rumbell T, Hof PR, Weaver CM. Functional consequences of age-related morphologic changes to pyramidal neurons of the rhesus monkey prefrontal cortex. J Comput Neurosci 2015; 38:263-83. [PMID: 25527184 PMCID: PMC4352129 DOI: 10.1007/s10827-014-0541-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 11/21/2014] [Accepted: 12/03/2014] [Indexed: 11/26/2022]
Abstract
Layer 3 (L3) pyramidal neurons in the lateral prefrontal cortex (LPFC) of rhesus monkeys exhibit dendritic regression, spine loss and increased action potential (AP) firing rates during normal aging. The relationship between these structural and functional alterations, if any, is unknown. To address this issue, morphological and electrophysiological properties of L3 LPFC pyramidal neurons from young and aged rhesus monkeys were characterized using in vitro whole-cell patch-clamp recordings and high-resolution digital reconstruction of neurons. Consistent with our previous studies, aged neurons exhibited significantly reduced dendritic arbor length and spine density, as well as increased input resistance and firing rates. Computational models using the digital reconstructions with Hodgkin-Huxley and AMPA channels allowed us to assess relationships between demonstrated age-related changes and to predict physiological changes that have not yet been tested empirically. For example, the models predict that in both backpropagating APs and excitatory postsynaptic currents (EPSCs), attenuation is lower in aged versus young neurons. Importantly, when identical densities of passive parameters and voltage- and calcium-gated conductances were used in young and aged model neurons, neither input resistance nor firing rates differed between the two age groups. Tuning passive parameters for each model predicted significantly higher membrane resistance (R m ) in aged versus young neurons. This R m increase alone did not account for increased firing rates in aged models, but coupling these R m values with subtle differences in morphology and membrane capacitance did. The predicted differences in passive parameters (or parameters with similar effects) are mathematically plausible, but must be tested empirically.
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Affiliation(s)
- Patrick J. Coskren
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Jennifer I. Luebke
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118 USA
| | - Doron Kabaso
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Susan L. Wearne
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Aniruddha Yadav
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Timothy Rumbell
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Patrick R. Hof
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
| | - Christina M. Weaver
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029 USA
- Department of Mathematics and Computer Science, Franklin and Marshall College, Lancaster, PA 17604 USA
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72
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Haile Y, Nakhaei-Nejad M, Boakye PA, Baker G, Smith PA, Murray AG, Giuliani F, Jahroudi N. Reprogramming of HUVECs into induced pluripotent stem cells (HiPSCs), generation and characterization of HiPSC-derived neurons and astrocytes. PLoS One 2015; 10:e0119617. [PMID: 25789622 PMCID: PMC4366250 DOI: 10.1371/journal.pone.0119617] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 02/02/2015] [Indexed: 11/30/2022] Open
Abstract
Neurodegenerative diseases are characterized by chronic and progressive structural or functional loss of neurons. Limitations related to the animal models of these human diseases have impeded the development of effective drugs. This emphasizes the need to establish disease models using human-derived cells. The discovery of induced pluripotent stem cell (iPSC) technology has provided novel opportunities in disease modeling, drug development, screening, and the potential for “patient-matched” cellular therapies in neurodegenerative diseases. In this study, with the objective of establishing reliable tools to study neurodegenerative diseases, we reprogrammed human umbilical vein endothelial cells (HUVECs) into iPSCs (HiPSCs). Using a novel and direct approach, HiPSCs were differentiated into cells of central nervous system (CNS) lineage, including neuronal, astrocyte and glial cells, with high efficiency. HiPSCs expressed embryonic genes such as nanog, sox2 and Oct-3/4, and formed embryoid bodies that expressed markers of the 3 germ layers. Expression of endothelial-specific genes was not detected in HiPSCs at RNA or protein levels. HiPSC-derived neurons possess similar morphology but significantly longer neurites compared to primary human fetal neurons. These stem cell-derived neurons are susceptible to inflammatory cell-mediated neuronal injury. HiPSC-derived neurons express various amino acids that are important for normal function in the CNS. They have functional receptors for a variety of neurotransmitters such as glutamate and acetylcholine. HiPSC-derived astrocytes respond to ATP and acetylcholine by elevating cytosolic Ca2+ concentrations. In summary, this study presents a novel technique to generate differentiated and functional HiPSC-derived neurons and astrocytes. These cells are appropriate tools for studying the development of the nervous system, the pathophysiology of various neurodegenerative diseases and the development of potential drugs for their treatments.
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Affiliation(s)
- Yohannes Haile
- Department of Medicine, University of Alberta, Edmonton, Canada
| | | | - Paul A. Boakye
- Department of Pharmacology, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Glen Baker
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Department of Psychiatry (Neurochemical Research Unit), University of Alberta, Edmonton, Canada
| | - Peter A. Smith
- Department of Pharmacology, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Allan G. Murray
- Department of Medicine, University of Alberta, Edmonton, Canada
| | - Fabrizio Giuliani
- Department of Medicine, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- * E-mail: (NJ); (FG)
| | - Nadia Jahroudi
- Department of Medicine, University of Alberta, Edmonton, Canada
- * E-mail: (NJ); (FG)
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73
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Dhupia N, Rathour RK, Narayanan R. Dendritic atrophy constricts functional maps in resonance and impedance properties of hippocampal model neurons. Front Cell Neurosci 2015; 8:456. [PMID: 25628537 PMCID: PMC4289900 DOI: 10.3389/fncel.2014.00456] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 12/16/2014] [Indexed: 11/23/2022] Open
Abstract
A gradient in the density of hyperpolarization-activated cyclic-nucleotide gated (HCN) channels is necessary for the emergence of several functional maps within hippocampal pyramidal neurons. Here, we systematically analyzed the impact of dendritic atrophy on nine such functional maps, related to input resistance and local/transfer impedance properties, using conductance-based models of hippocampal pyramidal neurons. We introduced progressive dendritic atrophy in a CA1 pyramidal neuron reconstruction through a pruning algorithm, measured all functional maps in each pruned reconstruction, and arrived at functional forms for the dependence of underlying measurements on dendritic length. We found that, across frequencies, atrophied neurons responded with higher efficiency to incoming inputs, and the transfer of signals across the dendritic tree was more effective in an atrophied reconstruction. Importantly, despite the presence of identical HCN-channel density gradients, spatial gradients in input resistance, local/transfer resonance frequencies and impedance profiles were significantly constricted in reconstructions with dendritic atrophy, where these physiological measurements across dendritic locations converged to similar values. These results revealed that, in atrophied dendritic structures, the presence of an ion channel density gradient alone was insufficient to sustain homologous functional maps along the same neuronal topograph. We assessed the biophysical basis for these conclusions and found that this atrophy-induced constriction of functional maps was mediated by an enhanced spatial spread of the influence of an HCN-channel cluster in atrophied trees. These results demonstrated that the influence fields of ion channel conductances need to be localized for channel gradients to express themselves as homologous functional maps, suggesting that ion channel gradients are necessary but not sufficient for the emergence of functional maps within single neurons.
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Affiliation(s)
- Neha Dhupia
- Cellular Neurophysiology Laboratory, Indian Institute of Science Bangalore, India ; Centre for Converging Technologies, University of Rajasthan Jaipur, India
| | - Rahul K Rathour
- Cellular Neurophysiology Laboratory, Indian Institute of Science Bangalore, India
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Indian Institute of Science Bangalore, India
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74
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Mishra P, Narayanan R. High-conductance states and A-type K+ channels are potential regulators of the conductance-current balance triggered by HCN channels. J Neurophysiol 2015; 113:23-43. [DOI: 10.1152/jn.00601.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An increase in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel conductance reduces input resistance, whereas the consequent increase in the inward h current depolarizes the membrane. This results in a delicate and unique conductance-current balance triggered by the expression of HCN channels. In this study, we employ experimentally constrained, morphologically realistic, conductance-based models of hippocampal neurons to explore certain aspects of this conductance-current balance. First, we found that the inclusion of an experimentally determined gradient in A-type K+ conductance, but not in M-type K+ conductance, tilts the HCN conductance-current balance heavily in favor of conductance, thereby exerting an overall restorative influence on neural excitability. Next, motivated by the well-established modulation of neuronal excitability by synaptically driven high-conductance states observed under in vivo conditions, we inserted thousands of excitatory and inhibitory synapses with different somatodendritic distributions. We measured the efficacy of HCN channels, independently and in conjunction with other channels, in altering resting membrane potential (RMP) and input resistance ( Rin) when the neuron received randomized or rhythmic synaptic bombardments through variable numbers of synaptic inputs. We found that the impact of HCN channels on average RMP, Rin, firing frequency, and peak-to-peak voltage response was severely weakened under high-conductance states, with the impinging synaptic drive playing a dominant role in regulating these measurements. Our results suggest that the debate on the role of HCN channels in altering excitability should encompass physiological and pathophysiological neuronal states under in vivo conditions and the spatiotemporal interactions of HCN channels with other channels.
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Affiliation(s)
- Poonam Mishra
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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75
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Martin YB, Negredo P, Villacorta-Atienza JA, Avendaño C. Trigeminal intersubnuclear neurons: morphometry and input-dependent structural plasticity in adult rats. J Comp Neurol 2014; 522:1597-617. [PMID: 24178892 DOI: 10.1002/cne.23494] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 10/11/2013] [Accepted: 10/15/2013] [Indexed: 11/09/2022]
Abstract
Intersubnuclear neurons in the caudal division of the spinal trigeminal nucleus that project to the principal nucleus (Pr5) play an active role in shaping the receptive fields of other neurons, at different levels in the ascending sensory system that processes information originating from the vibrissae. By using retrograde labeling and digital reconstruction, we investigated the morphometry and topology of the dendritic trees of these neurons and the changes induced by long-term experience-dependent plasticity in adult male rats. Primary afferent input was either eliminated by transection of the right infraorbital nerve (IoN), or selectively altered by repeated whisker clipping on the right side. These neurons do not display asymmetries between sides in basic metric and topologic parameters (global number of trees, nodes, spines, or dendritic ends), although neurons on the left tend to have longer terminal segments. Ipsilaterally, both deafferentation (IoN transection) and deprivation (whisker trimming) reduced the density of spines, and the former also caused a global increase in total dendritic length and a relative increase in more complex arbors. Contralaterally, deafferentation reduced more complex dendritic trees, and caused a moderate decline in dendritic length and spatial reach, and a loss of spines in number and density. Deprivation caused a similar, but more profound, effect on spines. Our findings provide original quantitative descriptions of a scarcely known cell population, and show that denervation- or deprivation-derived plasticity is expressed not only by neurons at higher levels of the sensory pathways, but also by neurons in key subcortical circuits for sensory processing.
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Affiliation(s)
- Yasmina B Martin
- Department of Anatomy, Histology, & Neuroscience, Autonoma University of Madrid, 28029, Madrid, Spain; Department of Anatomy, Francisco de Vitoria University, 28223, Pozuelo de Alarcón, Madrid, Spain
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76
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de Sousa G, Maex R, Adams R, Davey N, Steuber V. Dendritic morphology predicts pattern recognition performance in multi-compartmental model neurons with and without active conductances. J Comput Neurosci 2014; 38:221-34. [PMID: 25380637 PMCID: PMC4350002 DOI: 10.1007/s10827-014-0537-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 09/06/2014] [Accepted: 10/20/2014] [Indexed: 11/29/2022]
Abstract
In this paper we examine how a neuron’s dendritic morphology can affect its pattern recognition performance. We use two different algorithms to systematically explore the space of dendritic morphologies: an algorithm that generates all possible dendritic trees with 22 terminal points, and one that creates representative samples of trees with 128 terminal points. Based on these trees, we construct multi-compartmental models. To assess the performance of the resulting neuronal models, we quantify their ability to discriminate learnt and novel input patterns. We find that the dendritic morphology does have a considerable effect on pattern recognition performance and that the neuronal performance is inversely correlated with the mean depth of the dendritic tree. The results also reveal that the asymmetry index of the dendritic tree does not correlate with the performance for the full range of tree morphologies. The performance of neurons with dendritic tapering is best predicted by the mean and variance of the electrotonic distance of their synapses to the soma. All relationships found for passive neuron models also hold, even in more accentuated form, for neurons with active membranes.
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Affiliation(s)
- Giseli de Sousa
- Connectionism and Cognitive Science Laboratory, Department of Informatics and Statistics, Federal University of Santa Catarina, Campus Universitário, Trindade, 88040-970, Florianópolis, SC, Brazil,
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77
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Linking macroscopic with microscopic neuroanatomy using synthetic neuronal populations. PLoS Comput Biol 2014; 10:e1003921. [PMID: 25340814 PMCID: PMC4207466 DOI: 10.1371/journal.pcbi.1003921] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 09/17/2014] [Indexed: 12/15/2022] Open
Abstract
Dendritic morphology has been shown to have a dramatic impact on neuronal function. However, population features such as the inherent variability in dendritic morphology between cells belonging to the same neuronal type are often overlooked when studying computation in neural networks. While detailed models for morphology and electrophysiology exist for many types of single neurons, the role of detailed single cell morphology in the population has not been studied quantitatively or computationally. Here we use the structural context of the neural tissue in which dendritic trees exist to drive their generation in silico. We synthesize the entire population of dentate gyrus granule cells, the most numerous cell type in the hippocampus, by growing their dendritic trees within their characteristic dendritic fields bounded by the realistic structural context of (1) the granule cell layer that contains all somata and (2) the molecular layer that contains the dendritic forest. This process enables branching statistics to be linked to larger scale neuroanatomical features. We find large differences in dendritic total length and individual path length measures as a function of location in the dentate gyrus and of somatic depth in the granule cell layer. We also predict the number of unique granule cell dendrites invading a given volume in the molecular layer. This work enables the complete population-level study of morphological properties and provides a framework to develop complex and realistic neural network models. Computational models of neurons and neural networks provide a valuable avenue to test our understanding of brain regions and to make predictions to guide future experimentation. Each neuron has a unique dendritic tree, features of which can vary depending on the location of the neuron within the particular brain region. In this study, we generated a complete population of dendritic trees for the most numerous type of neuron in the hippocampus, the dentate gyrus granule cell, using a realistic three-dimensional structural context to drive the generation process. Morphological properties can now be studied at the level of complete neuronal populations, and this work provides a foundation to build upon in the construction of large-scale, data-driven neuroanatomical and network models.
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78
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Psarrou M, Stefanou SS, Papoutsi A, Tzilivaki A, Cutsuridis V, Poirazi P. A simulation study on the effects of dendritic morphology on layer V prefrontal pyramidal cell firing behavior. Front Cell Neurosci 2014; 8:287. [PMID: 25278837 PMCID: PMC4165233 DOI: 10.3389/fncel.2014.00287] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 08/29/2014] [Indexed: 11/13/2022] Open
Abstract
Pyramidal cells, the most abundant neurons in neocortex, exhibit significant structural variability across different brain areas and layers in different species. Moreover, in response to a somatic step current, these cells display a range of firing behaviors, the most common being (1) repetitive action potentials (Regular Spiking-RS), and (2) an initial cluster of 2-5 action potentials with short interspike interval (ISIs) followed by single spikes (Intrinsic Bursting-IB). A correlation between firing behavior and dendritic morphology has recently been reported. In this work we use computational modeling to investigate quantitatively the effects of the basal dendritic tree morphology on the firing behavior of 112 three-dimensional reconstructions of layer V PFC rat pyramidal cells. Particularly, we focus on how different morphological (diameter, total length, volume, and branch number) and passive [Mean Electrotonic Path length (MEP)] features of basal dendritic trees shape somatic firing when the spatial distribution of ionic mechanisms in the basal dendritic trees is uniform or non-uniform. Our results suggest that total length, volume and branch number are the best morphological parameters to discriminate the cells as RS or IB, regardless of the distribution of ionic mechanisms in basal trees. The discriminatory power of total length, volume, and branch number remains high in the presence of different apical dendrites. These results suggest that morphological variations in the basal dendritic trees of layer V pyramidal neurons in the PFC influence their firing patterns in a predictive manner and may in turn influence the information processing capabilities of these neurons.
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Affiliation(s)
- Maria Psarrou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece ; Centre for Computer Science and Informatics Research, Science and Technology Institute, University of Hertfordshire Hatfield, UK ; School of Computer Science, University of Hertfordshire Hatfield, UK
| | - Stefanos S Stefanou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece ; Department of Biology, University of Crete Heraklion, Greece
| | - Athanasia Papoutsi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece
| | - Alexandra Tzilivaki
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece ; Department of Biology, University of Crete Heraklion, Greece
| | - Vassilis Cutsuridis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas Heraklion, Greece
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79
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Kim H, Jones KE, Heckman CJ. Asymmetry in signal propagation between the soma and dendrites plays a key role in determining dendritic excitability in motoneurons. PLoS One 2014; 9:e95454. [PMID: 25083794 PMCID: PMC4118843 DOI: 10.1371/journal.pone.0095454] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Accepted: 03/27/2014] [Indexed: 12/31/2022] Open
Abstract
It is widely recognized that propagation of electrophysiological signals between the soma and dendrites of neurons differs depending on direction, i.e. it is asymmetric. How this asymmetry influences the activation of voltage-gated dendritic channels, and consequent neuronal behavior, remains unclear. Based on the analysis of asymmetry in several types of motoneurons, we extended our previous methodology for reducing a fully reconstructed motoneuron model to a two-compartment representation that preserved asymmetric signal propagation. The reduced models accurately replicated the dendritic excitability and the dynamics of the anatomical model involving a persistent inward current (PIC) dispersed over the dendrites. The relationship between asymmetric signal propagation and dendritic excitability was investigated using the reduced models while varying the asymmetry in signal propagation between the soma and the dendrite with PIC density constant. We found that increases in signal attenuation from soma to dendrites increased the activation threshold of a PIC (hypo-excitability), whereas increases in signal attenuation from dendrites to soma decreased the activation threshold of a PIC (hyper-excitability). These effects were so strong that reversing the asymmetry in the soma-to-dendrite vs. dendrite-to-soma attenuation, reversed the correlation between PIC threshold and distance of this current source from the soma. We propose the tight relation of the asymmetric signal propagation to the input resistance in the dendrites as a mechanism underlying the influence of the asymmetric signal propagation on the dendritic excitability. All these results emphasize the importance of maintaining the physiological asymmetry in dendritic signaling not only for normal function of the cells but also for biophysically realistic simulations of dendritic excitability.
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Affiliation(s)
- Hojeong Kim
- Division of Robotics Research, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, United States of America
- * E-mail:
| | - Kelvin E. Jones
- Centre for Neuroscience and Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Canada
| | - C. J. Heckman
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, United States of America
- Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, United States of America
- Department of Physical Therapy and Human Movement Science, Northwestern University Feinberg School of Medicine, Chicago, United States of America
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80
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Antidepressant-like effects of cortical deep brain stimulation coincide with pro-neuroplastic adaptations of serotonin systems. Biol Psychiatry 2014; 76:203-12. [PMID: 24503468 PMCID: PMC4072754 DOI: 10.1016/j.biopsych.2013.12.009] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 11/27/2013] [Accepted: 12/16/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND Cortical deep brain stimulation (DBS) is a promising therapeutic option for treatment-refractory depression, but its mode of action remains enigmatic. Serotonin (5-HT) systems are engaged indirectly by ventromedial prefrontal cortex (vmPFC) DBS. Resulting neuroplastic changes in 5-HT systems could thus coincide with the long-term therapeutic activity of vmPFC DBS. METHODS We tested this hypothesis by evaluating the antidepressant-like activity of vmPFC DBS in the chronic social defeat stress (CSDS) model of depression (n = 8-13 mice/group). Circuit-wide activation induced by vmPFC DBS was mapped with c-Fos immunolabeling. The effects of chronic vmPFC DBS on the physiology and morphology of genetically identified 5-HT cells from the dorsal raphe nucleus (DRN) were examined with whole-cell recording, somatodendritic three-dimensional reconstructions and morphometric analyses of presynaptic boutons along 5-HT axons. RESULTS Acute DBS drove c-Fos expression locally in the vmPFC and in several distal monosynaptically connected regions, including the DRN. Chronic DBS reversed CSDS-induced social avoidance, restored the disrupted balance of excitatory/inhibitory inputs onto 5-HT neurons, and reversed 5-HT hypoexcitability observed after CSDS. Furthermore, vmPFC DBS reversed CSDS-induced arborization of 5-HT dendrites in the DRN and increased the size and density of 5-HT presynaptic terminals in the dentate gyrus and vmPFC. CONCLUSIONS We validate a new preclinical paradigm to examine cellular mechanisms underlying the antidepressant-like activity of vmPFC DBS and identify dramatic circuit-mediated cellular adaptations that coincide with this treatment. These neuroplastic changes of 5-HT neurons might contribute to the progressive mood improvements reported in patients treated with chronic courses of cortical DBS.
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81
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Haile Y, Fu W, Shi B, Westaway D, Baker G, Jhamandas J, Giuliani F. Characterization of the NT2-derived neuronal and astrocytic cell lines as alternative in vitro models for primary human neurons and astrocytes. J Neurosci Res 2014; 92:1187-98. [PMID: 24801011 DOI: 10.1002/jnr.23399] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 03/01/2014] [Accepted: 03/30/2014] [Indexed: 12/22/2022]
Abstract
Primary human fetal neurons and astrocytes (HFNs and HFAs, respectively) provide relevant cell types with which to study in vitro the mechanisms involved in various human neurological diseases, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease. However, the limited availability of human fetal cells poses a significant problem for the study of these diseases when a human cell model system is required. Thus, generating a readily available alternative cell source with the essential features of human neurons and astrocytes is necessary. The human teratoma-derived NTera2/D1 (NT2) cell line is a promising tool from which both neuronal and glial cells can be generated. Nevertheless, a direct comparison of NT2 neurons and primary HFNs in terms of their morphology physiological and chemical properties is still missing. This study directly compares NT2-derived neurons and primary HFNs using immunocytochemistry, confocal calcium imaging, high-performance liquid chromatography, and high-content analysis techniques. We investigated the morphological similarities and differences, levels of relevant amino acids, and internal calcium fluctuations in response to certain neurotransmitters/stimuli. We also compared NT2-derived astrocytes and HFAs. In most of the parameters tested, both neuronal and astrocytic cell types exhibited similarities to primary human fetal neurons and astrocytes. NT2-derived neurons and astrocytes are reliable in vitro tools and a renewable cell source that can serve as a valid alternative to HFNs/HFAs for mechanistic studies of neurological diseases.
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Affiliation(s)
- Yohannes Haile
- Division of Neurology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
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82
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Groen MR, Paulsen O, Pérez-Garci E, Nevian T, Wortel J, Dekker MP, Mansvelder HD, van Ooyen A, Meredith RM. Development of dendritic tonic GABAergic inhibition regulates excitability and plasticity in CA1 pyramidal neurons. J Neurophysiol 2014; 112:287-99. [PMID: 24760781 DOI: 10.1152/jn.00066.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Synaptic plasticity rules change during development: while hippocampal synapses can be potentiated by a single action potential pairing protocol in young neurons, mature neurons require burst firing to induce synaptic potentiation. An essential component for spike timing-dependent plasticity is the backpropagating action potential (BAP). BAP along the dendrites can be modulated by morphology and ion channel composition, both of which change during late postnatal development. However, it is unclear whether these dendritic changes can explain the developmental changes in synaptic plasticity induction rules. Here, we show that tonic GABAergic inhibition regulates dendritic action potential backpropagation in adolescent, but not preadolescent, CA1 pyramidal neurons. These developmental changes in tonic inhibition also altered the induction threshold for spike timing-dependent plasticity in adolescent neurons. This GABAergic regulatory effect on backpropagation is restricted to distal regions of apical dendrites (>200 μm) and mediated by α5-containing GABA(A) receptors. Direct dendritic recordings demonstrate α5-mediated tonic GABA(A) currents in adolescent neurons which can modulate BAPs. These developmental modulations in dendritic excitability could not be explained by concurrent changes in dendritic morphology. To explain our data, model simulations propose a distally increasing or localized distal expression of dendritic α5 tonic inhibition in mature neurons. Overall, our results demonstrate that dendritic integration and plasticity in more mature dendrites are significantly altered by tonic α5 inhibition in a dendritic region-specific and developmentally regulated manner.
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Affiliation(s)
- Martine R Groen
- Center for Neurogenomics & Cognitive Research, Department of Integrative Neurophysiology, VU University Amsterdam, Amsterdam, The Netherlands
| | - Ole Paulsen
- Department of Physiology, Development and Neuroscience, Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | | | - Thomas Nevian
- Department of Physiology, University of Berne, Berne, Switzerland; and
| | - J Wortel
- Center for Neurogenomics & Cognitive Research, Department of Functional Genomics, VU University Amsterdam, Amsterdam, The Netherlands
| | - Marinus P Dekker
- Center for Neurogenomics & Cognitive Research, Department of Functional Genomics, VU University Amsterdam, Amsterdam, The Netherlands
| | - Huibert D Mansvelder
- Center for Neurogenomics & Cognitive Research, Department of Integrative Neurophysiology, VU University Amsterdam, Amsterdam, The Netherlands
| | - Arjen van Ooyen
- Center for Neurogenomics & Cognitive Research, Department of Integrative Neurophysiology, VU University Amsterdam, Amsterdam, The Netherlands
| | - Rhiannon M Meredith
- Center for Neurogenomics & Cognitive Research, Department of Integrative Neurophysiology, VU University Amsterdam, Amsterdam, The Netherlands;
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83
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The role of coupling strength and internal delay between compartments in shaping the bursting behavior of cortical neuron. Neurol Sci 2014; 35:883-9. [DOI: 10.1007/s10072-013-1619-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 12/19/2013] [Indexed: 11/30/2022]
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84
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Papoutsi A, Kastellakis G, Psarrou M, Anastasakis S, Poirazi P. Coding and decoding with dendrites. ACTA ACUST UNITED AC 2013; 108:18-27. [PMID: 23727338 DOI: 10.1016/j.jphysparis.2013.05.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 03/26/2013] [Accepted: 05/21/2013] [Indexed: 01/19/2023]
Abstract
Since the discovery of complex, voltage dependent mechanisms in the dendrites of multiple neuron types, great effort has been devoted in search of a direct link between dendritic properties and specific neuronal functions. Over the last few years, new experimental techniques have allowed the visualization and probing of dendritic anatomy, plasticity and integrative schemes with unprecedented detail. This vast amount of information has caused a paradigm shift in the study of memory, one of the most important pursuits in Neuroscience, and calls for the development of novel theories and models that will unify the available data according to some basic principles. Traditional models of memory considered neural cells as the fundamental processing units in the brain. Recent studies however are proposing new theories in which memory is not only formed by modifying the synaptic connections between neurons, but also by modifications of intrinsic and anatomical dendritic properties as well as fine tuning of the wiring diagram. In this review paper we present previous studies along with recent findings from our group that support a key role of dendrites in information processing, including the encoding and decoding of new memories, both at the single cell and the network level.
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Affiliation(s)
- Athanasia Papoutsi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology-Hellas (FORTH), Heraklion, Crete, Greece; Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - George Kastellakis
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology-Hellas (FORTH), Heraklion, Crete, Greece; Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - Maria Psarrou
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology-Hellas (FORTH), Heraklion, Crete, Greece
| | - Stelios Anastasakis
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology-Hellas (FORTH), Heraklion, Crete, Greece
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology-Hellas (FORTH), Heraklion, Crete, Greece.
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85
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Nowacki J, Osinga HM, Tsaneva-Atanasova KT. Continuation-Based Numerical Detection of After-Depolarization and Spike-Adding Thresholds. Neural Comput 2013; 25:877-900. [DOI: 10.1162/neco_a_00425] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The changes in neuronal firing pattern are signatures of brain function, and it is of interest to understand how such changes evolve as a function of neuronal biophysical properties. We address this important problem by the analysis and numerical investigation of a class of mechanistic mathematical models. We focus on a hippocampal pyramidal neuron model and study the occurrence of bursting related to the after-depolarization (ADP) that follows a brief current injection. This type of burst is a transient phenomenon that is not amenable to the classical bifurcation analysis done, for example, for periodic bursting oscillators. In this letter, we show how to formulate such transient behavior as a two-point boundary value problem (2PBVP), which can be solved using well-known continuation methods. The 2PBVP is formulated such that the transient response is represented by a finite orbit segment for which onsets of ADP and additional spikes in a burst can be detected as bifurcations during a one-parameter continuation. This in turn provides us with a direct method to approximate the boundaries of regions in a two-parameter plane where certain model behavior of interest occurs. More precisely, we use two-parameter continuation of the detected onset points to identify the boundaries between regions with and without ADP and bursts with different numbers of spikes. Our 2PBVP formulation is a novel approach to parameter sensitivity analysis that can be applied to a wide range of problems.
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Affiliation(s)
| | - Hinke M. Osinga
- Department of Mathematics, University of Auckland, Auckland 1142, New Zealand
| | - Krasimira T. Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol BS8 1TR, U.K
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86
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Hay E, Schürmann F, Markram H, Segev I. Preserving axosomatic spiking features despite diverse dendritic morphology. J Neurophysiol 2013; 109:2972-81. [PMID: 23536715 DOI: 10.1152/jn.00048.2013] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Throughout the nervous system, cells belonging to a certain electrical class (e-class)-sharing high similarity in firing response properties-may nevertheless have widely variable dendritic morphologies. To quantify the effect of this morphological variability on the firing of layer 5 thick-tufted pyramidal cells (TTCs), a detailed conductance-based model was constructed for a three-dimensional reconstructed exemplar TTC. The model exhibited spike initiation in the axon and reproduced the characteristic features of individual spikes, as well as of the firing properties at the soma, as recorded in a population of TTCs in young Wistar rats. When using these model parameters over the population of 28 three-dimensional reconstructed TTCs, both axonal and somatic ion channel densities had to be scaled linearly with the conductance load imposed on each of these compartments. Otherwise, the firing of model cells deviated, sometimes very significantly, from the experimental variability of the TTC e-class. The study provides experimentally testable predictions regarding the coregulation of axosomatic membrane ion channels density for cells with different dendritic conductance load, together with a simple and systematic method for generating reliable conductance-based models for the whole population of modeled neurons belonging to a particular e-class, with variable morphology as found experimentally.
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Affiliation(s)
- Etay Hay
- Interdisciplinary Center for Neural Computation and Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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87
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Influence of highly distinctive structural properties on the excitability of pyramidal neurons in monkey visual and prefrontal cortices. J Neurosci 2013; 32:13644-60. [PMID: 23035077 DOI: 10.1523/jneurosci.2581-12.2012] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Whole-cell patch-clamp recordings and high-resolution 3D morphometric analyses of layer 3 pyramidal neurons in in vitro slices of monkey primary visual cortex (V1) and dorsolateral granular prefrontal cortex (dlPFC) revealed that neurons in these two brain areas possess highly distinctive structural and functional properties. Area V1 pyramidal neurons are much smaller than dlPFC neurons, with significantly less extensive dendritic arbors and far fewer dendritic spines. Relative to dlPFC neurons, V1 neurons have a significantly higher input resistance, depolarized resting membrane potential, and higher action potential (AP) firing rates. Most V1 neurons exhibit both phasic and regular-spiking tonic AP firing patterns, while dlPFC neurons exhibit only tonic firing. Spontaneous postsynaptic currents are lower in amplitude and have faster kinetics in V1 than in dlPFC neurons, but are no different in frequency. Three-dimensional reconstructions of V1 and dlPFC neurons were incorporated into computational models containing Hodgkin-Huxley and AMPA receptor and GABA(A) receptor gated channels. Morphology alone largely accounted for observed passive physiological properties, but led to AP firing rates that differed more than observed empirically, and to synaptic responses that opposed empirical results. Accordingly, modeling predicts that active channel conductances differ between V1 and dlPFC neurons. The unique features of V1 and dlPFC neurons are likely fundamental determinants of area-specific network behavior. The compact electrotonic arbor and increased excitability of V1 neurons support the rapid signal integration required for early processing of visual information. The greater connectivity and dendritic complexity of dlPFC neurons likely support higher level cognitive functions including working memory and planning.
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88
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Abstract
Quantifying dendrite morphology is a method for determining the effect of biochemical pathways and extracellular agents on neuronal development and differentiation. Quantification can be performed using Sholl analysis, dendrite counting, and length quantification. These procedures can be performed on dendrite-forming cell lines or primary neurons grown in culture. In this protocol, we describe the use of a set of computer programs to assist in quantifying many aspects of dendrite morphology, including changes in total and localized arbor complexity.
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89
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El-Laithy K, Knorr M, Käs J, Bogdan M. Digital detection and analysis of branching and cell contacts in neural cell cultures. J Neurosci Methods 2012; 210:206-19. [DOI: 10.1016/j.jneumeth.2012.07.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 07/09/2012] [Accepted: 07/11/2012] [Indexed: 12/15/2022]
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90
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Tejada J, Arisi GM, García-Cairasco N, Roque AC. Morphological alterations in newly born dentate gyrus granule cells that emerge after status epilepticus contribute to make them less excitable. PLoS One 2012; 7:e40726. [PMID: 22811762 PMCID: PMC3394725 DOI: 10.1371/journal.pone.0040726] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 06/13/2012] [Indexed: 11/18/2022] Open
Abstract
Computer simulations of external current stimulations of dentate gyrus granule cells of rats with Status Epilepticus induced by pilocarpine and control rats were used to evaluate whether morphological differences alone between these cells have an impact on their electrophysiological behavior. The cell models were constructed using morphological information from tridimensional reconstructions with Neurolucida software. To evaluate the effect of morphology differences alone, ion channel conductances, densities and distributions over the dendritic trees of dentate gyrus granule cells were the same for all models. External simulated currents were injected in randomly chosen dendrites belonging to one of three different areas of dentate gyrus granule cell molecular layer: inner molecular layer, medial molecular layer and outer molecular layer. Somatic membrane potentials were recorded to determine firing frequencies and inter-spike intervals. The results show that morphologically altered granule cells from pilocarpine-induced epileptic rats are less excitable than control cells, especially when they are stimulated in the inner molecular layer, which is the target area for mossy fibers that sprout after pilocarpine-induced cell degeneration. This suggests that morphological alterations may act as a protective mechanism to allow dentate gyrus granule cells to cope with the increase of stimulation caused by mossy fiber sprouting.
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Affiliation(s)
- Julián Tejada
- Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil
| | - Gabriel M. Arisi
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil
| | - Norberto García-Cairasco
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (AR); (NG-C)
| | - Antonio C. Roque
- Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (AR); (NG-C)
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91
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van der Velden L, van Hooft JA, Chameau P. Altered dendritic complexity affects firing properties of cortical layer 2/3 pyramidal neurons in mice lacking the 5-HT3A receptor. J Neurophysiol 2012; 108:1521-8. [PMID: 22696545 DOI: 10.1152/jn.00829.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously shown that the serotonergic input on Cajal-Retzius cells, mediated by 5-HT(3) receptors, plays an important role in the early postnatal maturation of the apical dendritic trees of layer 2/3 pyramidal neurons. We reported that knockout mice lacking the 5-HT(3A) receptor showed exuberant apical dendrites of these cortical pyramidal neurons. Because model studies have shown the role of dendritic morphology on neuronal firing pattern, we used the 5-HT(3A) knockout mouse to explore the impact of dendritic hypercomplexity on the electrophysiological properties of this specific class of neurons. Our experimental results show that hypercomplexity of the apical dendritic tuft of layer 2/3 pyramidal neurons affects neuronal excitability by reducing the amount of spike frequency adaptation. This difference in firing pattern, related to a higher dendritic complexity, was accompanied by an altered development of the afterhyperpolarization slope with successive action potentials. Our abstract and realistic neuronal models, which allowed manipulation of the dendritic complexity, showed similar effects on neuronal excitability and confirmed the impact of apical dendritic complexity. Alterations of dendritic complexity, as observed in several pathological conditions such as neurodegenerative diseases or neurodevelopmental disorders, may thus not only affect the input to layer 2/3 pyramidal neurons but also shape their firing pattern and consequently alter the information processing in the cortex.
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Affiliation(s)
- Luuk van der Velden
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
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92
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Nowacki J, Osinga HM, Tsaneva-Atanasova K. Dynamical systems analysis of spike-adding mechanisms in transient bursts. JOURNAL OF MATHEMATICAL NEUROSCIENCE 2012; 2:7. [PMID: 22655748 PMCID: PMC3497719 DOI: 10.1186/2190-8567-2-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 02/13/2012] [Indexed: 05/03/2023]
Abstract
Transient bursting behaviour of excitable cells, such as neurons, is a common feature observed experimentally, but theoretically, it is not well understood. We analyse a five-dimensional simplified model of after-depolarisation that exhibits transient bursting behaviour when perturbed with a short current injection. Using one-parameter continuation of the perturbed orbit segment formulated as a well-posed boundary value problem, we show that the spike-adding mechanism is a canard-like transition that has a different character from known mechanisms for periodic burst solutions. The biophysical basis of the model gives a natural time-scale separation, which allows us to explain the spike-adding mechanism using geometric singular perturbation theory, but it does not involve actual bifurcations as for periodic bursts. We show that unstable sheets of the critical manifold, formed by saddle equilibria of the system that only exist in a singular limit, are responsible for the spike-adding transition; the transition is organised by the slow flow on the critical manifold near folds of this manifold. Our analysis shows that the orbit segment during the spike-adding transition includes a fast transition between two unstable sheets of the slow manifold that are of saddle type. We also discuss a different parameter regime where the presence of additional saddle equilibria of the full system alters the spike-adding mechanism.
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Affiliation(s)
- Jakub Nowacki
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Queen’s Building, University Walk, Bristol, BS8 1TR, United Kingdom
| | - Hinke M Osinga
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Krasimira Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Queen’s Building, University Walk, Bristol, BS8 1TR, United Kingdom
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93
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Myatt DR, Hadlington T, Ascoli GA, Nasuto SJ. Neuromantic - from semi-manual to semi-automatic reconstruction of neuron morphology. Front Neuroinform 2012; 6:4. [PMID: 22438842 PMCID: PMC3305991 DOI: 10.3389/fninf.2012.00004] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 02/20/2012] [Indexed: 02/05/2023] Open
Abstract
The ability to create accurate geometric models of neuronal morphology is important for understanding the role of shape in information processing. Despite a significant amount of research on automating neuron reconstructions from image stacks obtained via microscopy, in practice most data are still collected manually. This paper describes Neuromantic, an open source system for three dimensional digital tracing of neurites. Neuromantic reconstructions are comparable in quality to those of existing commercial and freeware systems while balancing speed and accuracy of manual reconstruction. The combination of semi-automatic tracing, intuitive editing, and ability of visualizing large image stacks on standard computing platforms provides a versatile tool that can help address the reconstructions availability bottleneck. Practical considerations for reducing the computational time and space requirements of the extended algorithm are also discussed.
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Affiliation(s)
- Darren R Myatt
- School of Systems Engineering, University of Reading Reading, UK
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94
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Ferri SL, Flanagan-Cato LM. Oxytocin and dendrite remodeling in the hypothalamus. Horm Behav 2012; 61:251-8. [PMID: 22326383 PMCID: PMC3312999 DOI: 10.1016/j.yhbeh.2012.01.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 01/13/2012] [Accepted: 01/14/2012] [Indexed: 10/14/2022]
Abstract
For most people, their quality of life depends on their successful interdependence with others, which requires sophisticated social cognition, communication, and emotional bonds. Across the lifespan, new bonds must be forged and maintained, and conspecific menaces must be managed. The dynamic nature of the human social landscape suggests ongoing specific alterations in neural circuitry across several brain systems to subserve social behavior. To discover the biological mechanisms that contribute to normal social activities, animal models of social behavior have been developed. One valuable model system has been female rat sexual behavior, which is governed by cyclic variation of ovarian hormones. This behavior is modulated by the neuropeptide oxytocin (OT) through its actions in the hypothalamic ventromedial nucleus (VMH). The fluctuation of this behavior is associated with dendrite remodeling, like several other examples of behavioral plasticity. This review compares hormone-induced plasticity in the VMH with other examples of dendrite plasticity across the mammalian nervous system, namely the neurobehavioral paradigms of environmental enrichment, chronic stress, and incentive sensitization, which affect the neocortex, hippocampal formation, and ventral striatum, respectively. This comparison suggests that the effects of ovarian hormones on VMH neurons in rats, given the simple dendritic arbor and short time course for dendrite remodeling, provide a dual opportunity for mechanistic and functional studies that will shed light on i) the neural actions of OT that regulate social behavior and, ii) behaviorally relevant dendrite regulation in a variety of brain structures. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.
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Affiliation(s)
- Sarah L Ferri
- Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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95
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Kurian M, Crook SM, Jung R. Motoneuron model of self-sustained firing after spinal cord injury. J Comput Neurosci 2011; 31:625-45. [PMID: 21526348 PMCID: PMC5036975 DOI: 10.1007/s10827-011-0324-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 12/31/2010] [Accepted: 03/20/2011] [Indexed: 11/25/2022]
Abstract
Under many conditions spinal motoneurons produce plateau potentials, resulting in self-sustained firing and providing a mechanism for translating short-lasting synaptic inputs into long-lasting motor output. During the acute-stage of spinal cord injury (SCI), the endogenous ability to generate plateaus is lost; however, during the chronic-stage of SCI, plateau potentials reappear with prolonged self-sustained firing that has been implicated in the development of spasticity. In this work, we extend previous modeling studies to systematically investigate the mechanisms underlying the generation of plateau potentials in motoneurons, including the influences of specific ionic currents, the morphological characteristics of the soma and dendrite, and the interactions between persistent inward currents and synaptic input. In particular, the goal of these computational studies is to explore the possible interactions between morphological and electrophysiological changes that occur after incomplete SCI. Model results predict that some of the morphological changes generally associated with the chronic-stage for some types of spinal cord injuries can cause a decrease in self-sustained firing. This and other computational results presented here suggest that the observed increases in self-sustained firing following some types of SCI may occur mainly due to changes in membrane conductances and changes in synaptic activity, particularly changes in the strength and timing of inhibition.
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Affiliation(s)
- Mini Kurian
- School of Mathematical and Statistical Sciences, Center for Adaptive Neural Systems, Arizona State University, Tempe, AZ 85287, USA
| | - Sharon M. Crook
- School of Mathematical and Statistical Sciences, Center for Adaptive Neural Systems, Arizona State University, Tempe, AZ 85287, USA; School of Life Sciences, Center for Adaptive Neural Systems, Arizona State University, Tempe, AZ 85287, USA
| | - Ranu Jung
- School of Biological and Health Systems Engineering, Center for Adaptive Neural Systems, Arizona State University, Tempe, AZ 85287, USA
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96
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Burst firing transitions in two-compartment pyramidal neuron induced by the perturbation of membrane capacitance. Neurol Sci 2011; 33:595-604. [PMID: 22037696 DOI: 10.1007/s10072-011-0819-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 10/06/2011] [Indexed: 10/15/2022]
Abstract
Neuronal membrane capacitance C (m) is one of the prominent factors in action potential initiation and propagation and then influences the firing patterns of neurons. Exploring the roles that C (m) plays in different firing patterns can facilitate the understanding of how different factors might influence neuronal firing behaviors. However, the impacts of variations in C (m) on neuronal firing patterns have been only partly explored until now. In this study, the influence of C (m) on burst firing behaviors of a two-compartment pyramidal neuron (including somatic compartment and dendritic compartment) was investigated by means of computer simulation, the value of C (m) in each compartment was denoted as C (m,s) and C (m,d), respectively. Two cases were considered, in the first case, we let C (m,s) =C (m,d), and then changed them simultaneously. While in the second case, we assumed C (m,s) ≠C (m,d), and then changed them, respectively. From the simulation results obtained from these two cases, it was found that the variation of C (m) in the somatic compartment and the dendritic compartment show much difference, simulated results obtained from the variation of C (m,d) have much more similarities than that of C (m,s) when comparing with the results obtained in the first case under which C (m,s) =C (m,d). These different effects of C (m,s) and C (m,d) on neuronal firing behaviors may result from the different topology and functional roles of soma and dendrites. Numerical results demonstrated in this paper may give us some inspiration in understanding the possible roles of C (m) in burst firing patterns, especially their transitions in compartmental neurons.
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97
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Conserved properties of dendritic trees in four cortical interneuron subtypes. Sci Rep 2011; 1:89. [PMID: 22355608 PMCID: PMC3216575 DOI: 10.1038/srep00089] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 08/22/2011] [Indexed: 11/26/2022] Open
Abstract
Dendritic trees influence synaptic integration and neuronal excitability, yet appear to develop in rather arbitrary patterns. Using electron microscopy and serial reconstructions, we analyzed the dendritic trees of four morphologically distinct neocortical interneuron subtypes to reveal two underlying organizational principles common to all. First, cross-sectional areas at any given point within a dendrite were proportional to the summed length of all dendritic segments distal to that point. Consistent with this observation, total cross-sectional area was almost perfectly conserved at bifurcation points. Second, dendritic cross-sections became progressively more elliptical at more proximal, larger diameter, dendritic locations. Finally, computer simulations revealed that these conserved morphological features limit distance dependent filtering of somatic EPSPs and facilitate distribution of somatic depolarization into all dendritic compartments. Because these features were shared by all interneurons studied, they may represent common organizational principles underlying the otherwise diverse morphology of dendritic trees.
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98
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Kasevich RS, LaBerge D. Theory of electric resonance in the neocortical apical dendrite. PLoS One 2011; 6:e23412. [PMID: 21853129 PMCID: PMC3154468 DOI: 10.1371/journal.pone.0023412] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 07/16/2011] [Indexed: 11/18/2022] Open
Abstract
Pyramidal neurons of the neocortex display a wide range of synchronous EEG rhythms, which arise from electric activity along the apical dendrites of neocortical pyramidal neurons. Here we present a theoretical description of oscillation frequency profiles along apical dendrites which exhibit resonance frequencies in the range of 10 to 100 Hz. The apical dendrite is modeled as a leaky coaxial cable coated with a dielectric, in which a series of compartments act as coupled electric circuits that gradually narrow the resonance profile. The tuning of the peak frequency is assumed to be controlled by the average amplitude of voltage-gated outward currents, which in turn are regulated by the subthreshold noise in the thousands of synaptic spines that are continuously bombarded by local circuits. The results of simulations confirmed the ability of the model both to tune the peak frequency in the 10–100 Hz range and to gradually narrow the resonance profile. Considerable additional narrowing of the resonance profile is provided by repeated looping through the apical dendrite via the corticothalamocortical circuit, which reduced the width of each resonance curve (at half-maximum) to approximately 1 Hz. Synaptic noise in the neural circuit is discussed in relation to the ways it can influence the narrowing process.
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Affiliation(s)
- Ray S. Kasevich
- Stanley Laboratory of Electrical Physics, Great Barrington, Massachusetts, United States of America
| | - David LaBerge
- Department of Cognitive Sciences, University of California Irvine, Irvine, California, United States of America
- * E-mail:
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99
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van Elburg RAJ. Stochastic continuous time neurite branching models with tree and segment dependent rates. J Theor Biol 2011; 276:159-73. [PMID: 21295594 DOI: 10.1016/j.jtbi.2011.01.039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/11/2011] [Accepted: 01/26/2011] [Indexed: 11/26/2022]
Abstract
In this paper we introduce a continuous time stochastic neurite branching model closely related to the discrete time stochastic BES-model. The discrete time BES-model is underlying current attempts to simulate cortical development, but is difficult to analyze. The new continuous time formulation facilitates analytical treatment thus allowing us to examine the structure of the model more closely. We derive explicit expressions for the time dependent probabilities p(γ,t) for finding a tree γ at time t, valid for arbitrary continuous time branching models with tree and segment dependent branching rates. We show, for the specific case of the continuous time BES-model, that as expected from our model formulation, the sums needed to evaluate expectation values of functions of the terminal segment number μ(f(n),t) do not depend on the distribution of the total branching probability over the terminal segments. In addition, we derive a system of differential equations for the probabilities p(n,t) of finding n terminal segments at time t. For the continuous BES-model, this system of differential equations gives direct numerical access to functions only depending on the number of terminal segments, and we use this to evaluate the development of the mean and standard deviation of the number of terminal segments at a time t. For comparison we discuss two cases where mean and variance of the number of terminal segments are exactly solvable. Then we discuss the numerical evaluation of the S-dependence of the solutions for the continuous time BES-model. The numerical results show clearly that higher S values, i.e. values such that more proximal terminal segments have higher branching rates than more distal terminal segments, lead to more symmetrical trees as measured by three tree symmetry indicators.
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Affiliation(s)
- Ronald A J van Elburg
- Department of Artificial Intelligence, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, The Netherlands.
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100
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Reimers-Kipping S, Hevers W, Pääbo S, Enard W. Humanized Foxp2 specifically affects cortico-basal ganglia circuits. Neuroscience 2010; 175:75-84. [PMID: 21111790 DOI: 10.1016/j.neuroscience.2010.11.042] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 11/18/2010] [Accepted: 11/19/2010] [Indexed: 01/06/2023]
Abstract
It has been proposed that two amino acid substitutions in the transcription factor FOXP2 have been positively selected during human evolution and influence aspects of speech and language. Recently it was shown that when these substitutions are introduced into the endogenous Foxp2 gene of mice, they increase dendrite length and long-term depression (LTD) in medium spiny neurons of the striatum. Here we investigated if these effects are found in other brain regions. We found that neurons in the cerebral cortex, the thalamus and the striatum have increased dendrite lengths in the humanized mice whereas neurons in the amygdala and the cerebellum do not. In agreement with previous work we found increased LTD in medium spiny neurons, but did not detect alterations of synaptic plasticity in Purkinje cells. We conclude that although Foxp2 is expressed in many brain regions and has multiple roles during mammalian development, the evolutionary changes that occurred in the protein in human ancestors specifically affect brain regions that are connected via cortico-basal ganglia circuits.
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Affiliation(s)
- S Reimers-Kipping
- Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6,D-04103 Leipzig, Germany
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