1
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Anil S, Lu H, Rotter S, Vlachos A. Repetitive transcranial magnetic stimulation (rTMS) triggers dose-dependent homeostatic rewiring in recurrent neuronal networks. PLoS Comput Biol 2023; 19:e1011027. [PMID: 37956202 PMCID: PMC10681319 DOI: 10.1371/journal.pcbi.1011027] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 11/27/2023] [Accepted: 10/11/2023] [Indexed: 11/15/2023] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique used to induce neuronal plasticity in healthy individuals and patients. Designing effective and reproducible rTMS protocols poses a major challenge in the field as the underlying biomechanisms of long-term effects remain elusive. Current clinical protocol designs are often based on studies reporting rTMS-induced long-term potentiation or depression of synaptic transmission. Herein, we employed computational modeling to explore the effects of rTMS on long-term structural plasticity and changes in network connectivity. We simulated a recurrent neuronal network with homeostatic structural plasticity among excitatory neurons, and demonstrated that this mechanism was sensitive to specific parameters of the stimulation protocol (i.e., frequency, intensity, and duration of stimulation). Particularly, the feedback-inhibition initiated by network stimulation influenced the net stimulation outcome and hindered the rTMS-induced structural reorganization, highlighting the role of inhibitory networks. These findings suggest a novel mechanism for the lasting effects of rTMS, i.e., rTMS-induced homeostatic structural plasticity, and highlight the importance of network inhibition in careful protocol design, standardization, and optimization of stimulation.
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Affiliation(s)
- Swathi Anil
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Han Lu
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
| | - Stefan Rotter
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
| | - Andreas Vlachos
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation (NeuroModulBasics), Faculty of Medicine, University of Freiburg, Freiburg, Germany
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2
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Anil S, Lu H, Rotter S, Vlachos A. Repetitive transcranial magnetic stimulation (rTMS) triggers dose-dependent homeostatic rewiring in recurrent neuronal networks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.20.533396. [PMID: 36993387 PMCID: PMC10055183 DOI: 10.1101/2023.03.20.533396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique used to induce neuronal plasticity in healthy individuals and patients. Designing effective and reproducible rTMS protocols poses a major challenge in the field as the underlying biomechanisms remain elusive. Current clinical protocol designs are often based on studies reporting rTMS-induced long-term potentiation or depression of synaptic transmission. Herein, we employed computational modeling to explore the effects of rTMS on long-term structural plasticity and changes in network connectivity. We simulated a recurrent neuronal network with homeostatic structural plasticity between excitatory neurons, and demonstrated that this mechanism was sensitive to specific parameters of the stimulation protocol (i.e., frequency, intensity, and duration of stimulation). The feedback-inhibition initiated by network stimulation influenced the net stimulation outcome and hindered the rTMS-induced homeostatic structural plasticity, highlighting the role of inhibitory networks. These findings suggest a novel mechanism for the lasting effects of rTMS, i.e., rTMS-induced homeostatic structural plasticity, and highlight the importance of network inhibition in careful protocol design, standardization, and optimization of stimulation.
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Affiliation(s)
- Swathi Anil
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Han Lu
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
| | - Stefan Rotter
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Andreas Vlachos
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- Center BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation (NeuroModulBasics), Faculty of Medicine, University of Freiburg, Freiburg, Germany
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3
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Nayak M, Das D, Pradhan J, Ahmed R, Laureano-Melo R, Dandapat J. Epigenetic signature in neural plasticity: the journey so far and journey ahead. Heliyon 2022; 8:e12292. [PMID: 36590572 PMCID: PMC9798197 DOI: 10.1016/j.heliyon.2022.e12292] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 10/31/2022] [Accepted: 12/05/2022] [Indexed: 12/23/2022] Open
Abstract
Neural plasticity is a remarkable characteristic of the brain which allows neurons to rewire their structure in response to internal and external stimuli. Many external stimuli collectively referred to as 'epigenetic factors' strongly influence structural and functional reorganization of the brain, thereby acting as a potential driver of neural plasticity. DNA methylation and demethylation, histone acetylation, and deacetylation are some of the frontline epigenetic mechanisms behind neural plasticity. Epigenetic signature molecules (mostly proteins) play a pivotal role in epigenetic reprogramming. Though neuro-epigenetics is an incredibly important field of emerging research, the critical role of signature proteins associated with epigenetic alteration and their involvement in neural plasticity needs further attention. This study gives an integrated and systematic overview of the current state of knowledge with a clear idea of types of neural plasticity and the context-dependent role of epigenetic signature molecules and their modulation by some natural bioactive compounds.
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Affiliation(s)
- Madhusmita Nayak
- Post-Graduate Department of Biotechnology, Utkal University, Bhubaneswar 751004, Odisha, India,Centre of Excellence in Integrated Omics and Computational Biology, Utkal University, Bhubaneswar 751004, Odisha, India
| | - Diptimayee Das
- Post-Graduate Department of Biotechnology, Utkal University, Bhubaneswar 751004, Odisha, India,Faculty of Allied Health Science, Chettinad Academy of Research and Education, Chettinad Hospital and Research Institute, Chennai India
| | - Jyotsnarani Pradhan
- Post-Graduate Department of Biotechnology, Utkal University, Bhubaneswar 751004, Odisha, India,Corresponding author.
| | - R.G. Ahmed
- Division of Anatomy and Embryology, Zoology Department, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt
| | - Roberto Laureano-Melo
- Barra Mansa University Center, R. Ver. Pinho de Carvalho, 267, 27330-550, Barra Mansa, Rio de Janeiro, Brazil
| | - Jagneshwar Dandapat
- Post-Graduate Department of Biotechnology, Utkal University, Bhubaneswar 751004, Odisha, India,Centre of Excellence in Integrated Omics and Computational Biology, Utkal University, Bhubaneswar 751004, Odisha, India,Corresponding author.
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4
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Harris KM, Hubbard DD, Kuwajima M, Abraham WC, Bourne JN, Bowden JB, Haessly A, Mendenhall JM, Parker PH, Shi B, Spacek J. Dendritic Spine Density Scales with Microtubule Number in Rat Hippocampal Dendrites. Neuroscience 2022; 489:84-97. [PMID: 35218884 PMCID: PMC9038701 DOI: 10.1016/j.neuroscience.2022.02.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 02/16/2022] [Accepted: 02/18/2022] [Indexed: 12/14/2022]
Abstract
Microtubules deliver essential resources to and from synapses. Three-dimensional reconstructions in rat hippocampus reveal a sampling bias regarding spine density that needs to be controlled for dendrite caliber and resource delivery based on microtubule number. The strength of this relationship varies across dendritic arbors, as illustrated for area CA1 and dentate gyrus. In both regions, proximal dendrites had more microtubules than distal dendrites. For CA1 pyramidal cells, spine density was greater on thicker than thinner dendrites in stratum radiatum, or on the more uniformly thin terminal dendrites in stratum lacunosum moleculare. In contrast, spine density was constant across the cone shaped arbor of tapering dendrites from dentate granule cells. These differences suggest that thicker dendrites supply microtubules to subsequent dendritic branches and local dendritic spines, whereas microtubules in thinner dendrites need only provide resources to local spines. Most microtubules ran parallel to dendrite length and associated with long, presumably stable mitochondria, which occasionally branched into lateral dendritic branches. Short, presumably mobile, mitochondria were tethered to microtubules that bent and appeared to direct them into a thin lateral branch. Prior work showed that dendritic segments with the same number of microtubules had elevated resources in subregions of their dendritic shafts where spine synapses had enlarged, and spine clusters had formed. Thus, additional microtubules were not required for redistribution of resources locally to growing spines or synapses. These results provide new understanding about the potential for microtubules to regulate resource delivery to and from dendritic branches and locally among dendritic spines.
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Affiliation(s)
- Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States.
| | - Dusten D Hubbard
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Masaaki Kuwajima
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Wickliffe C Abraham
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Jennifer N Bourne
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Jared B Bowden
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Andrea Haessly
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - John M Mendenhall
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Patrick H Parker
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Bitao Shi
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Josef Spacek
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
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5
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Vergara P, Pino G, Vera J, Arancibia F, Sanhueza M. Heterogeneous CaMKII-Dependent Synaptic Compensations in CA1 Pyramidal Neurons From Acute Hippocampal Slices. Front Cell Neurosci 2022; 16:821088. [PMID: 35431809 PMCID: PMC9005847 DOI: 10.3389/fncel.2022.821088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Prolonged changes in neural activity trigger homeostatic synaptic plasticity (HSP) allowing neuronal networks to operate within functional ranges. Cell-wide or input-specific adaptations can be induced by pharmacological or genetic manipulations of activity, and by sensory deprivation. Reactive functional changes caused by deafferentation may partially share mechanisms with HSP. Acute hippocampal slices are a suitable model to investigate relatively rapid (hours) modifications occurring after denervation and explore the underlying mechanisms. As during slicing many afferents are cut, we conducted whole-cell recordings of miniature excitatory postsynaptic currents (mEPSCs) in CA1 pyramidal neurons to evaluate changes over the following 12 h. As Schaffer collaterals constitute a major glutamatergic input to these neurons, we also dissected CA3. We observed an average increment in mEPSCs amplitude and a decrease in decay time, suggesting synaptic AMPA receptor upregulation and subunit content modifications. Sorting mEPSC by rise time, a correlate of synapse location along dendrites, revealed amplitude raises at two separate domains. A specific frequency increase was observed in the same domains and was accompanied by a global, unspecific raise. Amplitude and frequency increments were lower at sites initially more active, consistent with local compensatory processes. Transient preincubation with a specific Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor either blocked or occluded amplitude and frequency upregulation in different synapse populations. Results are consistent with the concurrent development of different known CaMKII-dependent HSP processes. Our observations support that deafferentation causes rapid and diverse compensations resembling classical slow forms of adaptation to inactivity. These results may contribute to understand fast-developing homeostatic or pathological events after brain injury.
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6
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Moulin TC, Rayêe D, Schiöth HB. Dendritic spine density changes and homeostatic synaptic scaling: a meta-analysis of animal studies. Neural Regen Res 2022; 17:20-24. [PMID: 34100421 PMCID: PMC8451564 DOI: 10.4103/1673-5374.314283] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Mechanisms of homeostatic plasticity promote compensatory changes of cellular excitability in response to chronic changes in the network activity. This type of plasticity is essential for the maintenance of brain circuits and is involved in the regulation of neural regeneration and the progress of neurodegenerative disorders. One of the most studied homeostatic processes is synaptic scaling, where global synaptic adjustments take place to restore the neuronal firing rate to a physiological range by the modulation of synaptic receptors, neurotransmitters, and morphology. However, despite the comprehensive literature on the electrophysiological properties of homeostatic scaling, less is known about the structural adjustments that occur in the synapses and dendritic tree. In this study, we performed a meta-analysis of articles investigating the effects of chronic network excitation (synaptic downscaling) or inhibition (synaptic upscaling) on the dendritic spine density of neurons. Our results indicate that spine density is consistently reduced after protocols that induce synaptic scaling, independent of the intervention type. Then, we discuss the implication of our findings to the current knowledge on the morphological changes induced by homeostatic plasticity.
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Affiliation(s)
- Thiago C Moulin
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden; Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Danielle Rayêe
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, NY, USA
| | - Helgi B Schiöth
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden; Institute for Translational Medicine and Biotechnology, Sechenov First Moscow State Medical University, Moscow, Russia
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7
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Madadi Asl M, Vahabie AH, Valizadeh A, Tass PA. Spike-Timing-Dependent Plasticity Mediated by Dopamine and its Role in Parkinson's Disease Pathophysiology. FRONTIERS IN NETWORK PHYSIOLOGY 2022; 2:817524. [PMID: 36926058 PMCID: PMC10013044 DOI: 10.3389/fnetp.2022.817524] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/08/2022] [Indexed: 01/05/2023]
Abstract
Parkinson's disease (PD) is a multi-systemic neurodegenerative brain disorder. Motor symptoms of PD are linked to the significant dopamine (DA) loss in substantia nigra pars compacta (SNc) followed by basal ganglia (BG) circuit dysfunction. Increasing experimental and computational evidence indicates that (synaptic) plasticity plays a key role in the emergence of PD-related pathological changes following DA loss. Spike-timing-dependent plasticity (STDP) mediated by DA provides a mechanistic model for synaptic plasticity to modify synaptic connections within the BG according to the neuronal activity. To shed light on how DA-mediated STDP can shape neuronal activity and synaptic connectivity in the PD condition, we reviewed experimental and computational findings addressing the modulatory effect of DA on STDP as well as other plasticity mechanisms and discussed their potential role in PD pathophysiology and related network dynamics and connectivity. In particular, reshaping of STDP profiles together with other plasticity-mediated processes following DA loss may abnormally modify synaptic connections in competing pathways of the BG. The cascade of plasticity-induced maladaptive or compensatory changes can impair the excitation-inhibition balance towards the BG output nuclei, leading to the emergence of pathological activity-connectivity patterns in PD. Pre-clinical, clinical as well as computational studies reviewed here provide an understanding of the impact of synaptic plasticity and other plasticity mechanisms on PD pathophysiology, especially PD-related network activity and connectivity, after DA loss. This review may provide further insights into the abnormal structure-function relationship within the BG contributing to the emergence of pathological states in PD. Specifically, this review is intended to provide detailed information for the development of computational network models for PD, serving as testbeds for the development and optimization of invasive and non-invasive brain stimulation techniques. Computationally derived hypotheses may accelerate the development of therapeutic stimulation techniques and potentially reduce the number of related animal experiments.
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Affiliation(s)
- Mojtaba Madadi Asl
- Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran
| | - Abdol-Hossein Vahabie
- School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.,Department of Psychology, Faculty of Psychology and Education, University of Tehran, Tehran, Iran
| | - Alireza Valizadeh
- Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran
| | - Peter A Tass
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, United States
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8
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Asada-Utsugi M, Uemura K, Kubota M, Noda Y, Tashiro Y, Uemura TM, Yamakado H, Urushitani M, Takahashi R, Hattori S, Miyakawa T, Ageta-Ishihara N, Kobayashi K, Kinoshita M, Kinoshita A. Mice with cleavage-resistant N-cadherin exhibit synapse anomaly in the hippocampus and outperformance in spatial learning tasks. Mol Brain 2021; 14:23. [PMID: 33494786 PMCID: PMC7831172 DOI: 10.1186/s13041-021-00738-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 01/16/2021] [Indexed: 11/30/2022] Open
Abstract
N-cadherin is a homophilic cell adhesion molecule that stabilizes excitatory synapses, by connecting pre- and post-synaptic termini. Upon NMDA receptor (NMDAR) activation by glutamate, membrane-proximal domains of N-cadherin are cleaved serially by a-disintegrin-and-metalloprotease 10 (ADAM10) and then presenilin 1(PS1, catalytic subunit of the γ-secretase complex). To assess the physiological significance of the initial N-cadherin cleavage, we engineer the mouse genome to create a knock-in allele with tandem missense mutations in the mouse N-cadherin/Cadherin-2 gene (Cdh2 R714G, I715D, or GD) that confers resistance on proteolysis by ADAM10 (GD mice). GD mice showed a better performance in the radial maze test, with significantly less revisiting errors after intervals of 30 and 300 s than WT, and a tendency for enhanced freezing in fear conditioning. Interestingly, GD mice reveal higher complexity in the tufts of thorny excrescence in the CA3 region of the hippocampus. Fine morphometry with serial section transmission electron microscopy (ssTEM) and three-dimensional (3D) reconstruction reveals significantly higher synaptic density, significantly smaller PSD area, and normal dendritic spine volume in GD mice. This knock-in mouse has provided in vivo evidence that ADAM10-mediated cleavage is a critical step in N-cadherin shedding and degradation and involved in the structure and function of glutamatergic synapses, which affect the memory function.
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Affiliation(s)
- M. Asada-Utsugi
- School of Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Neurology, Shiga University of Medical Science, Seta-Tsukinowa-Cho Otsu, Shiga, 520-2192 Japan
| | - K. Uemura
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - M. Kubota
- School of Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Y. Noda
- School of Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Y. Tashiro
- School of Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - T. M. Uemura
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - H. Yamakado
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - M. Urushitani
- Department of Neurology, Shiga University of Medical Science, Seta-Tsukinowa-Cho Otsu, Shiga, 520-2192 Japan
| | - R. Takahashi
- Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - S. Hattori
- Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, 470-1192 Japan
| | - T. Miyakawa
- Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, 470-1192 Japan
| | - N. Ageta-Ishihara
- Division of Biological Sciences, Department of Molecular Biology, Nagoya University Graduate School of Science, Nagoya, 464-8602 Japan
| | - K. Kobayashi
- Department of Pharmacology, Graduate School of Medicine, Nippon Medical School, Tokyo, 113-8602 Japan
| | - M. Kinoshita
- Division of Biological Sciences, Department of Molecular Biology, Nagoya University Graduate School of Science, Nagoya, 464-8602 Japan
| | - A. Kinoshita
- School of Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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9
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Affiliation(s)
- Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
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10
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Nishiyama J. Plasticity of dendritic spines: Molecular function and dysfunction in neurodevelopmental disorders. Psychiatry Clin Neurosci 2019; 73:541-550. [PMID: 31215705 DOI: 10.1111/pcn.12899] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 06/04/2019] [Accepted: 06/06/2019] [Indexed: 02/06/2023]
Abstract
Dendritic spines are tiny postsynaptic protrusions from a dendrite that receive most of the excitatory synaptic input in the brain. Functional and structural changes in dendritic spines are critical for synaptic plasticity, a cellular model of learning and memory. Conversely, altered spine morphology and plasticity are common hallmarks of human neurodevelopmental disorders, such as intellectual disability and autism. The advances in molecular and optical techniques have allowed for exploration of dynamic changes in structure and signal transduction at single-spine resolution, providing significant insights into the molecular regulation underlying spine structural plasticity. Here, I review recent findings on: how synaptic stimulation leads to diverse forms of spine structural plasticity; how the associated biochemical signals are initiated and transmitted into neuronal compartments; and how disruption of single genes associated with neurodevelopmental disorders can lead to abnormal spine structure in human and mouse brains. In particular, I discuss the functions of the Ras superfamily of small GTPases in spatiotemporal regulation of the actin cytoskeleton and protein synthesis in dendritic spines. Multiple lines of evidence implicate disrupted Ras signaling pathways in the spine structural abnormalities observed in neurodevelopmental disorders. Both deficient and excessive Ras activities lead to disrupted spine structure and deficits in learning and memory. Dysregulation of spine Ras signaling, therefore, may play a key role in the pathogenesis of multiple neurodevelopmental disorders with distinct etiologies.
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Affiliation(s)
- Jun Nishiyama
- Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Medical School, Singapore
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11
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Trivino-Paredes JS, Nahirney PC, Pinar C, Grandes P, Christie BR. Acute slice preparation for electrophysiology increases spine numbers equivalently in the male and female juvenile hippocampus: a DiI labeling study. J Neurophysiol 2019; 122:958-969. [PMID: 31268808 DOI: 10.1152/jn.00332.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hippocampal slices are widely used for in vitro electrophysiological experiments to study underlying mechanisms for synaptic transmission and plasticity, and there is a growing appreciation for sex differences in synaptic plasticity. To date, several studies have shown that the process of making slices from male animals can induce synaptogenesis in cornu ammonis area 1 (CA1) pyramidal cells, but there is a paucity of data for females and other brain regions. In the current study we use microcrystals of the lipophilic carbocyanine dye DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) to stain individual neurons in the CA1 and dentate gyrus (DG) hippocampal subfields of postnatal day 21 male and female rats. We show that the preparation of sections for electrophysiology produces significant increases in spines in sections obtained from females, similar to that observed in males. We also show that the procedures used for in vitro electrophysiology also result in significant spine increases in the DG and CA1 subfields. These results demonstrate the utility of this refined DiI procedure for staining neuronal dendrites and spines. They also show, for the first time, that in vitro electrophysiology slice preparations enhance spine numbers on hippocampal cells equivalently in both juvenile females and males.NEW & NOTEWORTHY This study introduces a new DiI technique that elucidates differences in spine numbers in juvenile female and male hippocampus, and shows that slice preparations for hippocampal electrophysiology in vitro may mask these differences.
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Affiliation(s)
- J S Trivino-Paredes
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - P C Nahirney
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Island Medical Program, University of British Columbia, Victoria, British Columbia, Canada.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - C Pinar
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - P Grandes
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, Leioa, Vizcaya, Spain.,Achucarro Basque Center for Neuroscience, Science Park of the UPV/EHU, Leioa, Vizcaya, Spain
| | - B R Christie
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Island Medical Program, University of British Columbia, Victoria, British Columbia, Canada.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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12
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Voglewede RL, Vandemark KM, Davidson AM, DeWitt AR, Heffler MD, Trimmer EH, Mostany R. Reduced sensory-evoked structural plasticity in the aging barrel cortex. Neurobiol Aging 2019; 81:222-233. [PMID: 31323444 DOI: 10.1016/j.neurobiolaging.2019.06.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 06/15/2019] [Accepted: 06/15/2019] [Indexed: 10/26/2022]
Abstract
Impairments in synaptic connectivity have been linked to cognitive deficits in age-related neurodegenerative disorders and healthy aging. However, the anatomical and structural bases of these impairments have not been identified yet. A hallmark of neural plasticity in young adults is short-term synaptic rearrangement, yet aged animals already display higher synaptic turnover rates at the baseline. Using two-photon excitation (2PE) microscopy, we explored if this elevated turnover alters the aged brain's response to plasticity. Following a sensory-evoked plasticity protocol involving whisker stimulation, aged mice display reduced spine dynamics (gain, loss, and turnover), decreased spine clustering, and lower spine stability when compared to young adult mice. These results suggest a deficiency of the cortical neurons of aged mice to structurally incorporate new sensory experiences, in the form of clustered, long-lasting synapses, into already existing cortical circuits. This research provides the first evidence linking experience-dependent plasticity with in vivo spine dynamics in the aged brain and supports a model of both reduced synaptic plasticity and reduced synaptic tenacity in the aged somatosensory system.
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Affiliation(s)
- Rebecca L Voglewede
- Neuroscience Program, Tulane University School of Science and Engineering, New Orleans, LA, USA; Tulane Brain Institute, Tulane University, New Orleans, LA, USA; Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Kaeli M Vandemark
- Neuroscience Program, Tulane University School of Science and Engineering, New Orleans, LA, USA; Tulane Brain Institute, Tulane University, New Orleans, LA, USA
| | - Andrew M Davidson
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA; Department of Cell and Molecular Biology, Tulane University School of Science and Engineering, New Orleans, LA, USA
| | - Annie R DeWitt
- Neuroscience Program, Tulane University School of Science and Engineering, New Orleans, LA, USA; Tulane Brain Institute, Tulane University, New Orleans, LA, USA
| | - Marissa D Heffler
- Neuroscience Program, Tulane University School of Science and Engineering, New Orleans, LA, USA; Tulane Brain Institute, Tulane University, New Orleans, LA, USA; Department of Biomedical Engineering, Tulane University School of Science and Engineering, Lindy Boggs Center Suite 500, New Orleans, LA, USA
| | - Emma H Trimmer
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Ricardo Mostany
- Neuroscience Program, Tulane University School of Science and Engineering, New Orleans, LA, USA; Tulane Brain Institute, Tulane University, New Orleans, LA, USA; Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA.
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13
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Hobbiss AF, Ramiro-Cortés Y, Israely I. Homeostatic Plasticity Scales Dendritic Spine Volumes and Changes the Threshold and Specificity of Hebbian Plasticity. iScience 2018; 8:161-174. [PMID: 30317078 PMCID: PMC6187013 DOI: 10.1016/j.isci.2018.09.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 08/03/2018] [Accepted: 09/17/2018] [Indexed: 11/27/2022] Open
Abstract
Information is encoded in neural networks through changes in synaptic weights. Synaptic learning rules involve a combination of rapid Hebbian plasticity and slower homeostatic synaptic plasticity that regulates neuronal activity through global synaptic scaling. Hebbian and homeostatic plasticity have been extensively investigated, whereas much less is known about their interaction. Here we investigated structural and functional consequences of homeostatic plasticity at dendritic spines of mouse hippocampal neurons. We found that prolonged activity blockade induced spine growth, paralleling synaptic strength increases. Following activity blockade, glutamate uncaging-mediated stimulation at single spines led to size-dependent structural potentiation: smaller spines underwent robust growth, whereas larger spines remained unchanged. Moreover, spines near the stimulated spine exhibited volume changes following homeostatic plasticity, indicating that there was a breakdown of input specificity following homeostatic plasticity. Overall, these findings demonstrate that Hebbian and homeostatic plasticity interact to shape neural connectivity through non-uniform structural plasticity at inputs. Chronic activity blockade leads to enlarged hippocampal spines and structural scaling Homeostatic plasticity affects subsequent Hebbian plasticity according to size of spines Neighbors also grow after potentiation of single spines, compromising input specificity
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Affiliation(s)
| | - Yazmin Ramiro-Cortés
- Champalimaud Centre for the Unknown, Lisbon 1400-038, Portugal; Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Circuito exterior s/n, Ciudad de México 04510, México
| | - Inbal Israely
- Champalimaud Centre for the Unknown, Lisbon 1400-038, Portugal; Department of Pathology and Cell Biology in the Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neuroscience, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.
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14
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Ibrahim LA, Huang JJ, Wang SZ, Kim YJ, Zhang LI, Tao HW. Sparse Labeling and Neural Tracing in Brain Circuits by STARS Strategy: Revealing Morphological Development of Type II Spiral Ganglion Neurons. Cereb Cortex 2018; 31:5049854. [PMID: 29982390 DOI: 10.1093/cercor/bhy154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Indexed: 11/12/2022] Open
Abstract
Elucidating axonal and dendritic projection patterns of individual neurons is a key for understanding the cytoarchitecture of neural circuits in the brain. This requires genetic approaches to achieve Golgi-like sparse labeling of desired types of neurons. Here, we explored a novel strategy of stochastic gene activation with regulated sparseness (STARS), in which the stochastic choice between 2 competing Cre-lox recombination events is controlled by varying the lox efficiency and cassette length. In a created STARS transgenic mouse crossed with various Cre driver lines, sparse neuronal labeling with a relatively uniform level of sparseness was achieved across different brain regions and cell types in both central and peripheral nervous systems. Tracing of individual type II peripheral auditory fibers revealed for the first time that they undergo experience-dependent developmental refinement, which is impaired by attenuating external sound input. Our results suggest that STARS strategy can be applied for circuit mapping and sparse gene manipulation.
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Affiliation(s)
- Leena A Ibrahim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - Junxiang J Huang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Medical Biology Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - Sheng-Zhi Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Young J Kim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - L I Zhang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - H W Tao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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15
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Gallinaro JV, Rotter S. Associative properties of structural plasticity based on firing rate homeostasis in recurrent neuronal networks. Sci Rep 2018; 8:3754. [PMID: 29491474 PMCID: PMC5830542 DOI: 10.1038/s41598-018-22077-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 02/16/2018] [Indexed: 11/18/2022] Open
Abstract
Correlation-based Hebbian plasticity is thought to shape neuronal connectivity during development and learning, whereas homeostatic plasticity would stabilize network activity. Here we investigate another, new aspect of this dichotomy: Can Hebbian associative properties also emerge as a network effect from a plasticity rule based on homeostatic principles on the neuronal level? To address this question, we simulated a recurrent network of leaky integrate-and-fire neurons, in which excitatory connections are subject to a structural plasticity rule based on firing rate homeostasis. We show that a subgroup of neurons develop stronger within-group connectivity as a consequence of receiving stronger external stimulation. In an experimentally well-documented scenario we show that feature specific connectivity, similar to what has been observed in rodent visual cortex, can emerge from such a plasticity rule. The experience-dependent structural changes triggered by stimulation are long-lasting and decay only slowly when the neurons are exposed again to unspecific external inputs.
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Affiliation(s)
- Júlia V Gallinaro
- Bernstein Center Freiburg & Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany.
| | - Stefan Rotter
- Bernstein Center Freiburg & Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany
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16
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Styr B, Slutsky I. Imbalance between firing homeostasis and synaptic plasticity drives early-phase Alzheimer's disease. Nat Neurosci 2018; 21:463-473. [PMID: 29403035 DOI: 10.1038/s41593-018-0080-x] [Citation(s) in RCA: 186] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 01/08/2018] [Indexed: 12/18/2022]
Abstract
During recent years, the preclinical stage of Alzheimer's disease (AD) has become a major focus of research. Continued failures in clinical trials and the realization that early intervention may offer better therapeutic outcome triggered a conceptual shift from late-stage AD pathology to early-stage pathophysiology. While much effort has been directed at understanding the factors initiating AD, little is known about the principle basis underlying the disease progression at its early stages. In this Perspective, we suggest a hypothesis to explain the transition from 'silent' signatures of aberrant neural circuit activity to clinically evident memory impairments. Namely, we propose that failures in firing homeostasis and imbalance between firing stability and synaptic plasticity in cortico-hippocampal circuits represent the driving force of early disease progression. We analyze the main types of possible homeostatic failures and provide the essential conceptual framework for examining the causal link between dysregulation of firing homeostasis, aberrant neural circuit activity and memory-related plasticity impairments associated with early AD.
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Affiliation(s)
- Boaz Styr
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Inna Slutsky
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. .,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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17
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Berry KP, Nedivi E. Spine Dynamics: Are They All the Same? Neuron 2017; 96:43-55. [PMID: 28957675 DOI: 10.1016/j.neuron.2017.08.008] [Citation(s) in RCA: 314] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 05/03/2017] [Accepted: 08/04/2017] [Indexed: 11/19/2022]
Abstract
Since Cajal's first drawings of Golgi stained neurons, generations of researchers have been fascinated by the small protrusions, termed spines, studding many neuronal dendrites. Most excitatory synapses in the mammalian CNS are located on dendritic spines, making spines convenient proxies for excitatory synaptic presence. When in vivo imaging revealed that dendritic spines are dynamic structures, their addition and elimination were interpreted as excitatory synapse gain and loss, respectively. Spine imaging has since become a popular assay for excitatory circuit remodeling. In this review, we re-evaluate the validity of using spine dynamics as a straightforward reflection of circuit rewiring. Recent studies tracking both spines and synaptic markers in vivo reveal that 20% of spines lack PSD-95 and are short lived. Although they account for most spine dynamics, their remodeling is unlikely to impact long-term network structure. We discuss distinct roles that spine dynamics can play in circuit remodeling depending on synaptic content.
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Affiliation(s)
- Kalen P Berry
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Elly Nedivi
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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18
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Wrosch JK, Einem VV, Breininger K, Dahlmanns M, Maier A, Kornhuber J, Groemer TW. Rewiring of neuronal networks during synaptic silencing. Sci Rep 2017; 7:11724. [PMID: 28916806 PMCID: PMC5601899 DOI: 10.1038/s41598-017-11729-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 08/29/2017] [Indexed: 12/14/2022] Open
Abstract
Analyzing the connectivity of neuronal networks, based on functional brain imaging data, has yielded new insight into brain circuitry, bringing functional and effective networks into the focus of interest for understanding complex neurological and psychiatric disorders. However, the analysis of network changes, based on the activity of individual neurons, is hindered by the lack of suitable meaningful and reproducible methodologies. Here, we used calcium imaging, statistical spike time analysis and a powerful classification model to reconstruct effective networks of primary rat hippocampal neurons in vitro. This method enables the calculation of network parameters, such as propagation probability, path length, and clustering behavior through the measurement of synaptic activity at the single-cell level, thus providing a fuller understanding of how changes at single synapses translate to an entire population of neurons. We demonstrate that our methodology can detect the known effects of drug-induced neuronal inactivity and can be used to investigate the extensive rewiring processes affecting population-wide connectivity patterns after periods of induced neuronal inactivity.
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Affiliation(s)
- Jana Katharina Wrosch
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen, Germany.
| | - Vicky von Einem
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen, Germany.,Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University of Erlangen-Nürnberg, 91058, Erlangen, Germany
| | - Katharina Breininger
- Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University of Erlangen-Nürnberg, 91058, Erlangen, Germany
| | - Marc Dahlmanns
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen, Germany
| | - Andreas Maier
- Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University of Erlangen-Nürnberg, 91058, Erlangen, Germany
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen, Germany
| | - Teja Wolfgang Groemer
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen, Germany
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19
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Petrosini L, De Bartolo P, Cutuli D, Gelfo F. Perinatal 192 IgG-Saporin as Neuroteratogen. Curr Top Behav Neurosci 2017; 29:111-123. [PMID: 26695170 DOI: 10.1007/7854_2015_418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The immunotoxin 192 IgG-saporin selectively destroys basal forebrain cholinergic neurons that provide cholinergic input to the hippocampus, entire cortical mantle, amygdala, and olfactory bulb. Perinatal immunotoxic lesions by 192 IgG-saporin induce long-lasting cholinergic depletion mimicking a number of developmental disorders reported in humans. The perinatal injection of 192 IgG-saporin induces several brain modifications, which are observed in neocortex and hippocampus at short and long term. These plastic changes involve both structural (alterations in brain volume, neuronal morphology, and neurogenesis) and molecular (modulations of the levels of neurotransmitters and other proteins related to neurodegeneration) levels. Moreover, the perinatal injection of 192 IgG-saporin may interact with the brain plastic capacity to react to other injuries. Perinatal 192 IgG-saporin lesions allowed investigating the role of the basal forebrain cholinergic system in modulating behavioral functions in developing as well as adult rats. After perinatal cholinergic depletion, rats display reduced ultrasonic vocalizations as neonates, learning and exploratory deficits as juveniles, altered discriminative abilities, impulsive and perseverative behaviors, and memory deficits as adults. Overall, these findings underline the importance of cholinergic system integrity for the development of specific structural and functional features.
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Affiliation(s)
- Laura Petrosini
- IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143, Rome, Italy. .,Department of Psychology, University Sapienza of Rome, Via dei Marsi 78, 00185, Rome, Italy.
| | - Paola De Bartolo
- IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143, Rome, Italy.,Department of Sociological and Psychopedagogical Studies, University Guglielmo Marconi of Rome, Via Plinio 44, 00193, Rome, Italy
| | - Debora Cutuli
- IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143, Rome, Italy.,Department of Psychology, University Sapienza of Rome, Via dei Marsi 78, 00185, Rome, Italy
| | - Francesca Gelfo
- IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143, Rome, Italy.,Department of Systemic Medicine, University of Tor Vergata, Via Montpellier 1, 00133, Rome, Italy
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20
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Fauth M, Tetzlaff C. Opposing Effects of Neuronal Activity on Structural Plasticity. Front Neuroanat 2016; 10:75. [PMID: 27445713 PMCID: PMC4923203 DOI: 10.3389/fnana.2016.00075] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 06/16/2016] [Indexed: 12/21/2022] Open
Abstract
The connectivity of the brain is continuously adjusted to new environmental influences by several activity-dependent adaptive processes. The most investigated adaptive mechanism is activity-dependent functional or synaptic plasticity regulating the transmission efficacy of existing synapses. Another important but less prominently discussed adaptive process is structural plasticity, which changes the connectivity by the formation and deletion of synapses. In this review, we show, based on experimental evidence, that structural plasticity can be classified similar to synaptic plasticity into two categories: (i) Hebbian structural plasticity, which leads to an increase (decrease) of the number of synapses during phases of high (low) neuronal activity and (ii) homeostatic structural plasticity, which balances these changes by removing and adding synapses. Furthermore, based on experimental and theoretical insights, we argue that each type of structural plasticity fulfills a different function. While Hebbian structural changes enhance memory lifetime, storage capacity, and memory robustness, homeostatic structural plasticity self-organizes the connectivity of the neural network to assure stability. However, the link between functional synaptic and structural plasticity as well as the detailed interactions between Hebbian and homeostatic structural plasticity are more complex. This implies even richer dynamics requiring further experimental and theoretical investigations.
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Affiliation(s)
- Michael Fauth
- Department of Computational Neuroscience, Third Institute of Physics - Biophysics, Georg-August UniversityGöttingen, Germany; Bernstein Center for Computational NeuroscienceGöttingen, Germany
| | - Christian Tetzlaff
- Bernstein Center for Computational NeuroscienceGöttingen, Germany; Max Planck Institute for Dynamics and Self-OrganizationGöttingen, Germany
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21
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Watson DJ, Ostroff L, Cao G, Parker PH, Smith H, Harris KM. LTP enhances synaptogenesis in the developing hippocampus. Hippocampus 2016; 26:560-76. [PMID: 26418237 PMCID: PMC4811749 DOI: 10.1002/hipo.22536] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2015] [Indexed: 12/27/2022]
Abstract
In adult hippocampus, long-term potentiation (LTP) produces synapse enlargement while preventing the formation of new small dendritic spines. Here, we tested how LTP affects structural synaptic plasticity in hippocampal area CA1 of Long-Evans rats at postnatal day 15 (P15). P15 is an age of robust synaptogenesis when less than 35% of dendritic spines have formed. We hypothesized that LTP might therefore have a different effect on synapse structure than in adults. Theta-burst stimulation (TBS) was used to induce LTP at one site and control stimulation was delivered at an independent site, both within s. radiatum of the same hippocampal slice. Slices were rapidly fixed at 5, 30, and 120 min after TBS, and processed for analysis by three-dimensional reconstruction from serial section electron microscopy (3DEM). All findings were compared to hippocampus that was perfusion-fixed (PF) in vivo at P15. Excitatory and inhibitory synapses on dendritic spines and shafts were distinguished from synaptic precursors, including filopodia and surface specializations. The potentiated response plateaued between 5 and 30 min and remained potentiated prior to fixation. TBS resulted in more small spines relative to PF by 30 min. This TBS-related spine increase lasted 120 min, hence, there were substantially more small spines with LTP than in the control or PF conditions. In contrast, control test pulses resulted in spine loss relative to PF by 120 min, but not earlier. The findings provide accurate new measurements of spine and synapse densities and sizes. The added or lost spines had small synapses, took time to form or disappear, and did not result in elevated potentiation or depression at 120 min. Thus, at P15 the spines formed following TBS, or lost with control stimulation, appear to be functionally silent. With TBS, existing synapses were awakened and then new spines formed as potential substrates for subsequent plasticity.
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Affiliation(s)
- Deborah J. Watson
- Department of Neuroscience, Center for Learning and MemoryInstitute for Neuroscience, University of Texas at AustinAustinTexas78731
| | | | - Guan Cao
- Department of Neuroscience, Center for Learning and MemoryInstitute for Neuroscience, University of Texas at AustinAustinTexas78731
| | - Patrick H. Parker
- Department of Neuroscience, Center for Learning and MemoryInstitute for Neuroscience, University of Texas at AustinAustinTexas78731
| | - Heather Smith
- Department of Neuroscience, Center for Learning and MemoryInstitute for Neuroscience, University of Texas at AustinAustinTexas78731
| | - Kristen M. Harris
- Department of Neuroscience, Center for Learning and MemoryInstitute for Neuroscience, University of Texas at AustinAustinTexas78731
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22
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Raab-Graham KF, Workman ER, Namjoshi S, Niere F. Pushing the threshold: How NMDAR antagonists induce homeostasis through protein synthesis to remedy depression. Brain Res 2016; 1647:94-104. [PMID: 27125595 DOI: 10.1016/j.brainres.2016.04.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 04/04/2016] [Accepted: 04/07/2016] [Indexed: 12/17/2022]
Abstract
Healthy neurons have an optimal operating range, coded globally by the frequency of action potentials or locally by calcium. The maintenance of this range is governed by homeostatic plasticity. Here, we discuss how new approaches to treat depression alter synaptic activity. These approaches induce the neuron to recruit homeostatic mechanisms to relieve depression. Homeostasis generally implies that the direction of activity necessary to restore the neuron's critical operating range is opposite in direction to its current activity pattern. Unconventional antidepressant therapies-deep brain stimulation and NMDAR antagonists-alter the neuron's "depressed" state by pushing the neuron's current activity in the same direction but to the extreme edge. These therapies rally the intrinsic drive of neurons in the opposite direction, thereby allowing the cell to return to baseline activity, form new synapses, and restore proper communication. In this review, we discuss seminal studies on protein synthesis dependent homeostatic plasticity and their contribution to our understanding of molecular mechanisms underlying the effectiveness of NMDAR antagonists as rapid antidepressants. Rapid antidepressant efficacy is likely to require a cascade of mRNA translational regulation. Emerging evidence suggests that changes in synaptic strength or intrinsic excitability converge on the same protein synthesis pathways, relieving depressive symptoms. Thus, we address the question: Are there multiple homeostatic mechanisms that induce the neuron and neuronal circuits to self-correct to regulate mood in vivo? Targeting alternative ways to induce homeostatic protein synthesis may provide, faster, safer, and longer lasting antidepressants. This article is part of a Special Issue entitled SI:RNA Metabolism in Disease.
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Affiliation(s)
- Kimberly F Raab-Graham
- Center for Learning and Memory, Department of Neuroscience, Institute of Neuroscience, University of Texas at Austin, Austin, TX 78712, United States; Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, United States; Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, United States.
| | - Emily R Workman
- Center for Learning and Memory, Department of Neuroscience, Institute of Neuroscience, University of Texas at Austin, Austin, TX 78712, United States; Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, United States
| | - Sanjeev Namjoshi
- Center for Learning and Memory, Department of Neuroscience, Institute of Neuroscience, University of Texas at Austin, Austin, TX 78712, United States; Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, United States
| | - Farr Niere
- Center for Learning and Memory, Department of Neuroscience, Institute of Neuroscience, University of Texas at Austin, Austin, TX 78712, United States; Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, United States
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23
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Sanz-García A, Knafo S, Pereda-Pérez I, Esteban JA, Venero C, Armario A. Administration of the TrkB receptor agonist 7,8-dihydroxyflavone prevents traumatic stress-induced spatial memory deficits and changes in synaptic plasticity. Hippocampus 2016; 26:1179-88. [PMID: 27068341 DOI: 10.1002/hipo.22599] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2016] [Indexed: 01/18/2023]
Abstract
Post-traumatic stress disorder (PTSD) occurs after exposure to traumatic situations and it is characterized by cognitive deficits that include impaired explicit memory. The neurobiological bases of such PTSD-associated memory alterations are yet to be elucidated and no satisfactory treatment for them exists. To address this issue, we first studied whether a single exposure of young adult rats (60 days) to immobilization on boards (IMO), a putative model of PTSD, produces long-term behavioral effects (2-8 days) similar to those found in PTSD patients. Subsequently, we investigated whether the administration of the TrkB agonist 7,8-dihydroxyflavone (DHF) 8 h after stress (therapeutic window) ameliorated the PTSD-like effect of IMO and the associated changes in synaptic plasticity. A single IMO exposure induced a spatial memory impairment similar to that found in other animal models of PTSD or in PTSD patients. IMO also increased spine density and long-term potentiation (LTP) in the CA3-CA1 pathway. Significantly, DHF reverted both spatial memory impairment and the increase in LTP, while it produced no effect in the controls. These data provide novel insights into the possible neurobiological substrate for explicit memory impairment in PTSD patients, supporting the idea that the activation of the BDNF/TrkB pathway fulfils a protective role after severe stress. Administration of DHF in the aftermath of a traumatic experience might be relevant to prevent its long-term consequences. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Ancor Sanz-García
- Unitat De Fisiologia Animal (Facultat De Biociències), Universitat Autònoma De Barcelona, 08193 Bellaterra, Barcelona, Spain.,Institut De Neurociències, Universitat Autonòma De Barcelona, 08193 Bellaterra, Barcelona, Spain.,Red De Trastornos Adictivos (RTA), Instituto De Salud Carlos III, Madrid, Spain
| | - Shira Knafo
- IkerBasque Research Professor, Biophysics Unit (Unidad De Biofísica CSIC-UPV/EHU), Leioa, Bizkaia, Spain
| | | | - José A Esteban
- Deparment of Molecular Neurobiology, Centro De Biología Molecular "Severo Ochoa," Consejo Superior De Investigaciones Científicas (CSIC)/Universidad Autónoma De Madrid, Madrid, Spain
| | - César Venero
- Department of Psychobiology, Universidad Nacional De Educación a Distancia, Juan Del Rosal 10, Madrid, 28040, Spain
| | - Antonio Armario
- Unitat De Fisiologia Animal (Facultat De Biociències), Universitat Autònoma De Barcelona, 08193 Bellaterra, Barcelona, Spain.,Institut De Neurociències, Universitat Autonòma De Barcelona, 08193 Bellaterra, Barcelona, Spain.,Red De Trastornos Adictivos (RTA), Instituto De Salud Carlos III, Madrid, Spain
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24
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Neuronal Atrophy Early in Degenerative Ataxia Is a Compensatory Mechanism to Regulate Membrane Excitability. J Neurosci 2015; 35:11292-307. [PMID: 26269637 DOI: 10.1523/jneurosci.1357-15.2015] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Neuronal atrophy in neurodegenerative diseases is commonly viewed as an early event in a continuum that ultimately results in neuronal loss. In a mouse model of the polyglutamine disorder spinocerebellar ataxia type 1 (SCA1), we tested the hypothesis that cerebellar Purkinje neuron atrophy serves an adaptive role rather than being simply a nonspecific response to injury. In acute cerebellar slices from SCA1 mice, we find that Purkinje neuron pacemaker firing is initially normal but, with the onset of motor dysfunction, becomes disrupted, accompanied by abnormal depolarization. Remarkably, subsequent Purkinje cell atrophy is associated with a restoration of pacemaker firing. The early inability of Purkinje neurons to support repetitive spiking is due to unopposed calcium currents resulting from a reduction in large-conductance calcium-activated potassium (BK) and subthreshold-activated potassium channels. The subsequent restoration of SCA1 Purkinje neuron firing correlates with the recovery of the density of these potassium channels that accompanies cell atrophy. Supporting a critical role for BK channels, viral-mediated increases in BK channel expression in SCA1 Purkinje neurons improves motor dysfunction and partially restores Purkinje neuron morphology. Cerebellar perfusion of flufenamic acid, an agent that restores the depolarized membrane potential of SCA1 Purkinje neurons by activating potassium channels, prevents Purkinje neuron dendritic atrophy. These results suggest that Purkinje neuron dendritic remodeling in ataxia is an adaptive response to increases in intrinsic membrane excitability. Similar adaptive remodeling could apply to other vulnerable neuronal populations in neurodegenerative disease. SIGNIFICANCE STATEMENT In neurodegenerative disease, neuronal atrophy has long been assumed to be an early nonspecific event preceding neuronal loss. However, in a mouse model of spinocerebellar ataxia type 1 (SCA1), we identify a previously unappreciated compensatory role for neuronal shrinkage. Purkinje neuron firing in these mice is initially normal, but is followed by abnormal membrane depolarization resulting from a reduction in potassium channels. Subsequently, these electrophysiological effects are counteracted by cell atrophy, which by restoring normal potassium channel membrane density, re-establishes pacemaker firing. Reversing the initial membrane depolarization improved motor function and Purkinje neuron morphology in the SCA1 mice. These results suggest that Purkinje neuron remodeling in ataxia is an active compensatory response that serves to normalize intrinsic membrane excitability.
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Lesion-induced and activity-dependent structural plasticity of Purkinje cell dendritic spines in cerebellar vermis and hemisphere. Brain Struct Funct 2015; 221:3405-26. [PMID: 26420278 DOI: 10.1007/s00429-015-1109-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 09/09/2015] [Indexed: 10/23/2022]
Abstract
Neuroplasticity allows the brain to encode experience and learn behaviors, and also to re-acquire lost functions after damage. The cerebellum is a suitable structure to address this topic because of its strong involvement in learning processes and compensation of lesion-induced deficits. This study was aimed to characterize the effects of a hemicerebellectomy (HCb) combined or not with the exposition to environmental enrichment (EE) on dendritic spine density and size in Purkinje cell proximal and distal compartments of cerebellar vermian and hemispherical regions. Male Wistar rats were housed in enriched or standard environments from the 21st post-natal day (pnd) onwards. At the 75th pnd, rats were submitted to HCb or sham lesion. Neurological symptoms and spatial performance in the Morris water maze were evaluated. At the end of testing, morphological analyses assessed dendritic spine density, area, length, and head diameter on vermian and hemispherical Purkinje cells. All hemicerebellectomized (HCbed) rats showed motor compensation, but standard-reared HCbed animals exhibited cognitive impairment that was almost completely compensated in enriched HCbed rats. The standard-reared HCbed rats showed decreased density with augmented size of Purkinje cell spines in the vermis, and augmented both density and size in the hemisphere. Enriched HCbed rats almost completely maintained the spine density and size induced by EE. Both lesion-induced and activity-dependent cerebellar plastic changes may be interpreted as "beneficial" brain reactions, aimed to support behavioral performance rescuing.
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Abstract
Many, if not all, questions in biology and psychology today were formulated and considered in depth, though typically in a different language, from the 1700's to the early 1900's. However, because of politics or fashion, some topics fell out of favor or failed to recruit new scientists and hence languished. Despite greatly expanded scholarship in the history of the life sciences in the twentieth century, many such topics have had to be rediscovered in recent years, while much of the wisdom already accrued stays in the older literature and not in active minds. This is particularly true today when scientific advances appear at breakneck speed. It would not be an exaggeration to say that many 'breakthroughs' turn out really to be rediscoveries of forgotten observations. Two areas of particular significance to the interdisciplinary study of behavior are the Norms of Reaction (from Biology) and the concept of Plasticity (from Psychology). These and related fields benefit from the perspective of epigenetics so long as rigorous operational definitions are implemented. It is also important to revive Hogben's admonition that the interaction of hereditary and environment cannot be understood outside of the context of development. Five examples of increasing complexity in phenotypic plasticity in brain and behavior are presented to illustrate this perspective.
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Affiliation(s)
- David Crews
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Seth A Weisberg
- Institute of Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA
| | - Sahotra Sarkar
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
- Departments of Integrative Biology and Philosophy, The University of Texas at Austin, Austin, TX 78712, USA
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Yin J, Yuan Q. Structural homeostasis in the nervous system: a balancing act for wiring plasticity and stability. Front Cell Neurosci 2015; 8:439. [PMID: 25653587 PMCID: PMC4299450 DOI: 10.3389/fncel.2014.00439] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Accepted: 12/05/2014] [Indexed: 01/08/2023] Open
Abstract
Experience-dependent modifications of neural circuits provide the cellular basis for functional adaptation and learning, while presenting significant challenges to the stability of neural networks. The nervous system copes with these perturbations through a variety of compensatory mechanisms with distinct spatial and temporal profiles. Mounting evidence suggests that structural plasticity, through modifications of the number and structure of synapses, or changes in local and long-range connectivity, might contribute to the stabilization of network activity and serve as an important component of the homeostatic regulation of the nervous system. Conceptually similar to the homeostatic regulation of synaptic strength and efficacy, homeostatic structural plasticity has a profound and lasting impact on the intrinsic excitability of the neuron and circuit properties, yet remains largely unexplored. In this review, we examine recent reports describing structural modifications associated with functional compensation in both developing and adult nervous systems, and discuss the potential role for structural homeostasis in maintaining network stability and its implications in physiological and pathological conditions of the nervous systems.
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Affiliation(s)
- Jun Yin
- National Institute of Neurological Disorders and Stroke, National Institutes of Health Bethesda, MD, USA
| | - Quan Yuan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health Bethesda, MD, USA
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Kumar SS, Saraswathi P, Vijayaraghavan R. Effect of bacopa monniera on cold stress induced neurodegeneration in hippocampus of wistar rats: a histomorphometric study. J Clin Diagn Res 2015; 9:AF05-7. [PMID: 25737970 PMCID: PMC4347061 DOI: 10.7860/jcdr/2015/10199.5423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 11/08/2014] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Bacopa monniera/ Brahmi,is used over centuries in Ayurvedic medicine for memory development, learning, concentration and other mental illnesses such as nervousness and poor cognition. The present study aims to evaluate the effect of Bacopa monniera (Brahmi, BM) on cold stress induced histological changes in hippocampus of Wistar rats. MATERIALS AND METHODS Total 24 male rats divided into four groups were used (n=6) for this study. Group I was control in which rats were kept under ideal laboratory conditions, Group II was given 40 mg/kg of BM extract, Group III was cold water swim stress in which rats were forced to swim in the cold water maintained at 18±2(o)C till it started to sink for a period of one month and Group IV in which cold water swim stress given for a month followed by oral administration of BM extracts 40mg/kg treatment for a month. The whole study was carried out for a period of 60 d. The animals were sacrificed next day and their brains dissected out for histomorphometric analysis. The diameter, packing density and total number of neurons were calculated from stained histological section by using micrometry in the CA-1 region of the hippocampus. STATISTICAL ANALYSIS The analysis and plotting of graphs were carried out using Sigma Plot 12 (Systat Software Inc., USA). Values are expressed as Mean ± SEM (n = 6). One way analysis of variance followed by Student-Newman-Keul's multiple comparisons test was used for the comparison of means. A probability of 0.05 and less was taken as statistically significant. RESULTS The results showed that there is no significant difference in the diameter of the cells between the groups but total number of the cells in Group II was statistically significant when compared with the others groups. Student-Newman-Keuls method showed that Group II and Group IV are statistically significant when compared to Group III (p<0.05). CONCLUSION RESULTS indicates that when BM extracts administered orally produce neuroprotective effect in cold stress induced hippocampal neurodegeneration of rats. Hence, the herb BM can possibly be used as an adjuvant to improve memory to combat stress in our day to day life.
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Affiliation(s)
- Saravana S Kumar
- Lecturer, Department of Anatomy, Saveetha Dental College, Chennai, India
| | - P Saraswathi
- Professor, Department of Anatomy, Saveetha University, Chennai, India
| | - R Vijayaraghavan
- Professor, Department of Pharmacology and Research Director, Saveetha University, India
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Bell ME, Bourne JN, Chirillo MA, Mendenhall JM, Kuwajima M, Harris KM. Dynamics of nascent and active zone ultrastructure as synapses enlarge during long-term potentiation in mature hippocampus. J Comp Neurol 2014; 522:3861-84. [PMID: 25043676 PMCID: PMC4167938 DOI: 10.1002/cne.23646] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/23/2014] [Accepted: 06/30/2014] [Indexed: 11/08/2022]
Abstract
Nascent zones and active zones are adjacent synaptic regions that share a postsynaptic density, but nascent zones lack the presynaptic vesicles found at active zones. Here dendritic spine synapses were reconstructed through serial section electron microscopy (3DEM) and EM tomography to investigate nascent zone dynamics during long-term potentiation (LTP) in mature rat hippocampus. LTP was induced with theta-burst stimulation, and comparisons were made with control stimulation in the same hippocampal slices at 5 minutes, 30 minutes, and 2 hours post-induction and to perfusion-fixed hippocampus in vivo. Nascent zones were present at the edges of ∼35% of synapses in perfusion-fixed hippocampus and as many as ∼50% of synapses in some hippocampal slice conditions. By 5 minutes, small dense-core vesicles known to transport active zone proteins moved into more presynaptic boutons. By 30 minutes, nascent zone area decreased, without significant change in synapse area, suggesting that presynaptic vesicles were recruited to preexisting nascent zones. By 2 hours, both nascent and active zones were enlarged. Immunogold labeling revealed glutamate receptors in nascent zones; however, average distances from nascent zones to docked presynaptic vesicles ranged from 170 ± 5 nm in perfusion-fixed hippocampus to 251 ± 4 nm at enlarged synapses by 2 hours during LTP. Prior stochastic modeling suggests that decrease in glutamate concentration reduces the probability of glutamate receptor activation from 0.4 at the center of release to 0.1 just 200 nm away. Thus, conversion of nascent zones to functional active zones likely requires the recruitment of presynaptic vesicles during LTP.
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Affiliation(s)
- Maria Elizabeth Bell
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Jennifer N. Bourne
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Michael A. Chirillo
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
- The University of Texas Medical School, Houston, TX 77030
| | - John M. Mendenhall
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Masaaki Kuwajima
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Kristen M. Harris
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
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Abstract
Units of dendritic branches called dendritic spines represent more than simply decorative appendages of the neuron and actively participate in integrative functions of “spinous” nerve cells thereby contributing to the general phenomenon of synaptic plasticity. In animal models of drug addiction, spines are profoundly affected by treatments with drugs of abuse and represent important sub cellular markers which interfere deeply into the physiology of the neuron thereby providing an example of the burgeoning and rapidly increasing interest in “structural plasticity”. Medium Spiny Neurons (MSNs) of the Nucleus Accumbens (Nacc) show a reduced number of dendritic spines and a decrease in TH-positive terminals upon withdrawal from opiates, cannabinoids and alcohol. The reduction is localized “strictly” to second order dendritic branches where dopamine (DA)-containing terminals, impinging upon spines, make synaptic contacts. In addition, long-thin spines seems preferentially affected raising the possibility that cellular learning of these neurons may be selectively hampered. These findings suggest that dendritic spines are affected by drugs widely abused by humans and provide yet another example of drug-induced aberrant neural plasticity with marked reflections on the physiology of synapses, system structural organization, and neuronal circuitry remodeling.
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Affiliation(s)
- Saturnino Spiga
- Department of Animal Biology and Ecology, University of Cagliari Cagliari, Italy
| | - Giovanna Mulas
- Department of Animal Biology and Ecology, University of Cagliari Cagliari, Italy ; "G.Minardi" Laboratory of Cognitive Neuroscience, Department of Chemistry and Pharmacy, University of Sassari Sassari, Italy
| | - Francesca Piras
- Department of Animal Biology and Ecology, University of Cagliari Cagliari, Italy ; Department of Natural Science and the Territory, University of Sassari Sassari, Italy
| | - Marco Diana
- "G.Minardi" Laboratory of Cognitive Neuroscience, Department of Chemistry and Pharmacy, University of Sassari Sassari, Italy
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Kim A, Zamora-Martinez ER, Edwards S, Mandyam CD. Structural reorganization of pyramidal neurons in the medial prefrontal cortex of alcohol dependent rats is associated with altered glial plasticity. Brain Struct Funct 2014; 220:1705-20. [PMID: 24667898 PMCID: PMC4177030 DOI: 10.1007/s00429-014-0755-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 03/10/2014] [Indexed: 12/22/2022]
Abstract
In rodents, chronic intermittent ethanol vapor exposure (CIE) produces alcohol dependence, alters the activity of pyramidal neurons and decreases the number of glial progenitors in the medial prefrontal cortex (mPFC). Adult male Wistar rats were exposed to CIE and were injected with mitotic markers to label and phenotype proliferating cells to test the hypothesis that CIE produces concurrent alterations in the structure of pyramidal neurons and the cell cycle kinetics and developmental stages of glial progenitors in the mPFC. Medial prefrontal cortical tissue was processed for Golgi-Cox staining, immunohistochemistry and Western blotting analysis. CIE increased dendritic arborization and spine densities within basal and apical dendrites of pyramidal neurons via aberrant reorganization of actin cytoskeleton-associated molecules. CIE concomitantly increased the expression of total NR2B subunits without affecting phosphorylation of NR2B at Tyr-1472 or levels of PSD-95. CIE reduced the length of S-phase of the cell cycle of glial progenitors and reduced proliferation and differentiation of progenitors into bHLH transcription factor Olig2-expressing premyelinating oligodendrocyte progenitor cells (OPCs). CIE also produced a corresponding hyperphosphorylation of Olig2, and reduced expression of myelin basic protein. Our findings demonstrate that CIE-induced alterations in OPCs and myelin-related proteins are associated with profound alterations in the structure of pyramidal neurons. In sum, our results not only provide evidence that alcohol dependence leads to pathological changes in the mPFC, which may in part define a cellular basis for cognitive impairments associated with alcoholism, but also show dependence-associated morphological changes in the PFC at the single neuron level.
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Affiliation(s)
- Airee Kim
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
| | - Eva R. Zamora-Martinez
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
| | - Scott Edwards
- Department of Physiology, Alcohol & Drug Abuse Center of Excellence, LSU Health Sciences Center, New Orleans, LA, USA
| | - Chitra D. Mandyam
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
- Skaggs School of Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
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Abad S, Fole A, del Olmo N, Pubill D, Pallàs M, Junyent F, Camarasa J, Camins A, Escubedo E. MDMA enhances hippocampal-dependent learning and memory under restrictive conditions, and modifies hippocampal spine density. Psychopharmacology (Berl) 2014; 231:863-74. [PMID: 24158501 DOI: 10.1007/s00213-013-3304-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 09/23/2013] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Addictive drugs produce forms of structural plasticity in the nucleus accumbens and prefrontal cortex. The aim of this study was to investigate the impact of chronic MDMA exposure on pyramidal neurons in the CA1 region of hippocampus and drug-related spatial learning and memory changes. METHODS AND RESULTS Adolescent rats were exposed to saline or MDMA in a regime that mimicked chronic administration. One week later, when acquisition or reference memory was evaluated in a standard Morris water maze (MWM), no differences were obtained between groups. However, MDMA-exposed animals performed better when the MWM was implemented under more difficult conditions. Animals of MDMA group were less anxious and were more prepared to take risks, as in the open field test they ventured more frequently into the central area. We have demonstrated that MDMA caused an increase in brain-derived neurotrophic factor (BDNF) expression. When spine density was evaluated, MDMA-treated rats presented a reduced density when compared with saline, but overall, training increased the total number of spines, concluding that in MDMA-group, training prevented a reduction in spine density or induced its recovery. CONCLUSIONS This study provides support for the conclusion that binge administration of MDMA, known to be associated to neurotoxic damage of hippocampal serotonergic terminals, increases BDNF expression and stimulates synaptic plasticity when associated with training. In these conditions, adolescent rats perform better in a more difficult water maze task under restricted conditions of learning and memory. The effect on this task could be modulated by other behavioural changes provoked by MDMA.
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Affiliation(s)
- Sònia Abad
- Department of Pharmacology and Therapeutic Chemistry (Pharmacology Section) and Institute of Biomedicine (IBUB), University of Barcelona, Avda. Joan XXIII s/n, Barcelona, 08028, Spain
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c-Jun N-terminal kinase has a key role in Alzheimer disease synaptic dysfunction in vivo. Cell Death Dis 2014; 5:e1019. [PMID: 24457963 PMCID: PMC4040696 DOI: 10.1038/cddis.2013.559] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 12/16/2013] [Indexed: 12/14/2022]
Abstract
Altered synaptic function is considered one of the first features of Alzheimer disease (AD). Currently, no treatment is available to prevent the dysfunction of excitatory synapses in AD. Identification of the key modulators of synaptopathy is of particular significance in the treatment of AD. We here characterized the pathways leading to synaptopathy in TgCRND8 mice and showed that c-Jun N-terminal kinase (JNK) is activated at the spine prior to the onset of cognitive impairment. The specific inhibition of JNK, with its specific inhibiting peptide D-JNKI1, prevented synaptic dysfunction in TgCRND8 mice. D-JNKI1 avoided both the loss of postsynaptic proteins and glutamate receptors from the postsynaptic density and the reduction in size of excitatory synapses, reverting their dysfunction. This set of data reveals that JNK is a key signaling pathway in AD synaptic injury and that its specific inhibition offers an innovative therapeutic strategy to prevent spine degeneration in AD.
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Ramar S, P S. Histomorphometric study of fructus psoralea on ethanol induced neurodegeneration of hippocampus in rat. J Clin Diagn Res 2013; 7:1561-4. [PMID: 24086839 DOI: 10.7860/jcdr/2013/6596.3217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 07/09/2013] [Indexed: 11/24/2022]
Abstract
AIM The histomophometric study of Fructus Psoralea (FP) on ethanol induced neurodegeneration of hippocampus was investigated in a rat by using micrometry. MATERIAL AND METHODS The study was conducted on thirty healthy female adult wistar albino rats with regular 4-day estrus cycles. The experiment was carried out for a period of 2-4 months. The rats were divided into- SHAM operated control group (Group I) and experimental groups - overiectomised vehicle control rat ((Group II), OVX and orally treated with FP(Group III) OVX and induced with ethanol (Group IV), OVX rats induced with ethnaol and orally treated with FP (Group V). ANOVA tool was used to test the mean positive behavioural activity of all the groups. The diameter, packing density and the total number of neurons were calculated from toluidine blue stained histological section by using micrometry. The statistical package SPSS (17.0 VERSION) was used. Statistical significance was defined as p < 0.05. Data was expressed as mean ± SEM. DISCUSSION In animal studies, ethanol was found to significantly inhibit neuronal activity in the CA1 and CA3 pyramidal cell layers of the hippocampus. FP increase the number of cholinergic neurons in the basal forebrain which in turn leads to increased function of hippocampus, a structure heavily implicated in behavioural activity and memory consolidation. CONCLUSION People with extensive hippocampal damage may experience amnesia, learning and memory disabilities. Hence the herb FP may be used as an adjuvant to treat the above neurological disorders.
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Affiliation(s)
- Sivanandan Ramar
- Assistant Professor, Department of Anatomy, Madha Medical College and Research Institute , Chennai-600 122, India
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Beauparlant J, van den Brand R, Barraud Q, Friedli L, Musienko P, Dietz V, Courtine G. Undirected compensatory plasticity contributes to neuronal dysfunction after severe spinal cord injury. ACTA ACUST UNITED AC 2013; 136:3347-61. [PMID: 24080153 DOI: 10.1093/brain/awt204] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Severe spinal cord injury in humans leads to a progressive neuronal dysfunction in the chronic stage of the injury. This dysfunction is characterized by premature exhaustion of muscle activity during assisted locomotion, which is associated with the emergence of abnormal reflex responses. Here, we hypothesize that undirected compensatory plasticity within neural systems caudal to a severe spinal cord injury contributes to the development of neuronal dysfunction in the chronic stage of the injury. We evaluated alterations in functional, electrophysiological and neuromorphological properties of lumbosacral circuitries in adult rats with a staggered thoracic hemisection injury. In the chronic stage of the injury, rats exhibited significant neuronal dysfunction, which was characterized by co-activation of antagonistic muscles, exhaustion of locomotor muscle activity, and deterioration of electrochemically-enabled gait patterns. As observed in humans, neuronal dysfunction was associated with the emergence of abnormal, long-latency reflex responses in leg muscles. Analyses of circuit, fibre and synapse density in segments caudal to the spinal cord injury revealed an extensive, lamina-specific remodelling of neuronal networks in response to the interruption of supraspinal input. These plastic changes restored a near-normal level of synaptic input within denervated spinal segments in the chronic stage of injury. Syndromic analysis uncovered significant correlations between the development of neuronal dysfunction, emergence of abnormal reflexes, and anatomical remodelling of lumbosacral circuitries. Together, these results suggest that spinal neurons deprived of supraspinal input strive to re-establish their synaptic environment. However, this undirected compensatory plasticity forms aberrant neuronal circuits, which may engage inappropriate combinations of sensorimotor networks during gait execution.
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Lai KO, Ip NY. Structural plasticity of dendritic spines: the underlying mechanisms and its dysregulation in brain disorders. Biochim Biophys Acta Mol Basis Dis 2013; 1832:2257-63. [PMID: 24012719 DOI: 10.1016/j.bbadis.2013.08.012] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 08/13/2013] [Accepted: 08/28/2013] [Indexed: 12/17/2022]
Abstract
Dendritic spines are specialized structures on neuronal processes where the majority of excitatory synapses are localized. Spines are highly dynamic, and their stabilization and morphology are influenced by synaptic activity. This extrinsic regulation of spine morphogenesis underlies experience-dependent brain development and information storage within the brain circuitry. In this review, we summarize recent findings that demonstrate the phenomenon of activity-dependent structural plasticity and the molecular mechanisms by which synaptic activity sculpt neuronal connections. Impaired structural plasticity is associated with perturbed brain function in neurodevelopmental disorders such as autism. Information from the mechanistic studies therefore provides important insights into the design of therapeutic strategies for these brain disorders.
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Affiliation(s)
- Kwok-On Lai
- Division of Life Science, Molecular Neuroscience Center and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong
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Coulon M, Wellman CL, Marjara IS, Janczak AM, Zanella AJ. Early adverse experience alters dendritic spine density and gene expression in prefrontal cortex and hippocampus in lambs. Psychoneuroendocrinology 2013; 38:1112-21. [PMID: 23265310 DOI: 10.1016/j.psyneuen.2012.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/22/2012] [Accepted: 10/22/2012] [Indexed: 02/06/2023]
Abstract
In the laboratory, prenatal stress produces alterations in the structure and function of corticolimbic neurons. Here we report changes in gene expression and corticolimbic dendritic spine morphology in the offspring of pregnant ewes subjected to aversive interactions with human handlers during the last five weeks of pregnancy (AVS) compared to control dams that received gentle handling (GEN). AVS lambs had higher spine density on pyramidal neurons in area CA1 of the hippocampus and in medial prefrontal cortex compared to GEN lambs, as well as a lower ratio of mushroom spines to stubby and thin spines in area CA1. Expression of genes involved in brain development and spine morphogenesis was decreased in hippocampus and prefrontal cortex in AVS compared to GEN lambs. This study is the first demonstration that an ecologically relevant aversive experience in a field setting alters neuronal structure similarly to previous reports from laboratory settings and that even for animals domesticated over 12,000 years ago, an apparently mild stressor, resulting from human-animal interactions, can have similarly profound impacts on corticolimbic morphology.
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Affiliation(s)
- Marjorie Coulon
- Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, Oslo, Norway.
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Morley BJ, Mervis RF. Dendritic spine alterations in the hippocampus and parietal cortex of alpha7 nicotinic acetylcholine receptor knockout mice. Neuroscience 2012; 233:54-63. [PMID: 23270857 DOI: 10.1016/j.neuroscience.2012.12.025] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 12/10/2012] [Accepted: 12/12/2012] [Indexed: 12/19/2022]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is involved in higher cognitive and memory functions, and is associated with the etiology of neurological diseases involving cognitive decline, including Alzheimer's disease (AD). We hypothesized that spine changes in the α7 knockout might help to explain the behavioral deficits observed in α7 knockout mice and prodromal hippocampal changes in AD. We quantified several measures of dendritic morphology in the CA1 region of the mouse hippocampus in Golgi-stained material from wildtype and α7 knockout mice at P24. The most significant difference was a 64% increase in thin (L-type) dendritic spines on the CA1 basilar tree in knockout mice (p<.05). There were small decreases in the number of in N-type (-15%), M-type (-14%) and D-type (-4%) spine densities. The CA1 basilar dendritic tree of knockout mice had significantly less branching in the regions near the soma in comparison with wildtype animals (p<.01), but not in the more distal branching. Changes in the configuration of CA1 basilar dendritic spines have been observed in a number of experimental paradigms, suggesting that basilar dendritic spines are highly plastic. One component of cognitive dysfunction may be through α7-modulated GABAergic interneurons synapsing on CA1 basal dendrites.
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Affiliation(s)
- B J Morley
- Boys Town National Research Hospital, 555 North 30th Street, Omaha, NE 68131, USA.
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Orlowski D, Elfving B, Müller HK, Wegener G, Bjarkam CR. Wistar rats subjected to chronic restraint stress display increased hippocampal spine density paralleled by increased expression levels of synaptic scaffolding proteins. Stress 2012; 15:514-23. [PMID: 22128856 DOI: 10.3109/10253890.2011.643516] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The aim of this study was to investigate whether the previously reported effect of chronic restraint stress (CRS) on hippocampal neuron morphology and spine density is paralleled by a similar change in the expression levels of synaptic scaffolding proteins. Adult male Wistar rats were subjected either to CRS (6 h/day) for 21 days or to control conditions. The resulting brains were divided and one hemisphere was impregnated with Golgi-Cox before coronal sectioning and autometallographic development. Neurons from CA1, CA3b, CA3c, and dentate gyrus (DG) area were reconstructed and subjected to Sholl analysis and spine density estimation. The contralateral hippocampus was used for quantitative real-time polymerase chain reaction and protein analysis of genes associated with spine density and morphology (the synaptic scaffolding proteins: Spinophilin, Homer1-3, and Shank1-3). In the CA3c area, CRS decreased the number of apical dendrites and their total length, whereas CA1 and DG spine density were significantly increased. Analysis of the contralateral hippocampal homogenate displayed an increased gene expression of Spinophilin, Homer1, Shank1, and Shank2 and increased protein expression of Spinophilin and Homer1 in the CRS animals. In conclusion, CRS influences hippocampal neuroplasticity by modulation of dendrite branching pattern and spine density paralleled by increased expression levels of synaptic scaffolding proteins.
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Affiliation(s)
- D Orlowski
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus C, Denmark.
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40
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Orlowski D, Bjarkam CR. A simple reproducible and time saving method of semi-automatic dendrite spine density estimation compared to manual spine counting. J Neurosci Methods 2012; 208:128-33. [DOI: 10.1016/j.jneumeth.2012.05.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 04/27/2012] [Accepted: 05/08/2012] [Indexed: 10/28/2022]
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41
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Bidirectional control of mRNA translation and synaptic plasticity by the cytoplasmic polyadenylation complex. Mol Cell 2012; 47:253-66. [PMID: 22727665 DOI: 10.1016/j.molcel.2012.05.016] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 01/18/2012] [Accepted: 05/03/2012] [Indexed: 11/22/2022]
Abstract
Translational control of mRNAs in dendrites is essential for certain forms of synaptic plasticity and learning and memory. CPEB is an RNA-binding protein that regulates local translation in dendrites. Here, we identify poly(A) polymerase Gld2, deadenylase PARN, and translation inhibitory factor neuroguidin (Ngd) as components of a dendritic CPEB-associated polyadenylation apparatus. Synaptic stimulation induces phosphorylation of CPEB, PARN expulsion from the ribonucleoprotein complex, and polyadenylation in dendrites. A screen for mRNAs whose polyadenylation is altered by Gld2 depletion identified >100 transcripts including one encoding NR2A, an NMDA receptor subunit. shRNA depletion studies demonstrate that Gld2 promotes and Ngd inhibits dendritic NR2A expression. Finally, shRNA-mediated depletion of Gld2 in vivo attenuates protein synthesis-dependent long-term potentiation (LTP) at hippocampal dentate gyrus synapses; conversely, Ngd depletion enhances LTP. These results identify a pivotal role for polyadenylation and the opposing effects of Gld2 and Ngd in hippocampal synaptic plasticity.
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42
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Aramuni G, Griesbeck O. Chronic calcium imaging in neuronal development and disease. Exp Neurol 2012; 242:50-6. [PMID: 22374357 DOI: 10.1016/j.expneurol.2012.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 12/05/2011] [Accepted: 02/13/2012] [Indexed: 12/12/2022]
Abstract
Neuronal circuits develop, adjust to experience and degenerate in response to injury or disease in the course of weeks and months. Available recording techniques, however, typically sample physiological properties of identified neurons on the time scale of minutes and hours. Thus, in order to obtain a full understanding of a long term physiological process data need to be extrapolated from numerous experimental sessions and animals, often collected blindly and under variable conditions. The generation and ongoing engineering of genetically encoded calcium indicators creates an opportunity to repeatedly record activity from the same individual neurons in vivo over weeks, months and potentially the entire lifetime of a model organism. Chronic calcium imaging with genetically encoded indicators thus may allow to establish functional biographies of identified neuronal cell types in the brain and to reveal the physiological relevance of structural changes as they occur under natural and pathological conditions.
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Affiliation(s)
- Gayane Aramuni
- Max-Planck-Institut für Neurobiologie, Am Klopferspitz 18, 82152 Martinsried, Germany
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43
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Abstract
Synaptic plasticity is the experience-dependent change in connectivity between neurons that is believed to underlie learning and memory. Here, we discuss the cellular and molecular processes that are altered when a neuron responds to external stimuli, and how these alterations lead to an increase or decrease in synaptic connectivity. Modification of synaptic components and changes in gene expression are necessary for many forms of plasticity. We focus on excitatory neurons in the mammalian hippocampus, one of the best-studied model systems of learning-related plasticity.
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Affiliation(s)
- Victoria M Ho
- Interdepartmental Program in Neurosciences, University of California-Los Angeles (UCLA), BSRB 390B, 615 Charles E. Young Drive South, Los Angeles, CA 90095-1737, USA
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44
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Bourne JN, Harris KM. Coordination of size and number of excitatory and inhibitory synapses results in a balanced structural plasticity along mature hippocampal CA1 dendrites during LTP. Hippocampus 2011; 21:354-73. [PMID: 20101601 DOI: 10.1002/hipo.20768] [Citation(s) in RCA: 217] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Enlargement of dendritic spines and synapses correlates with enhanced synaptic strength during long-term potentiation (LTP), especially in immature hippocampal neurons. Less clear is the nature of this structural synaptic plasticity on mature hippocampal neurons, and nothing is known about the structural plasticity of inhibitory synapses during LTP. Here the timing and extent of structural synaptic plasticity and changes in local protein synthesis evidenced by polyribosomes were systematically evaluated at both excitatory and inhibitory synapses on CA1 dendrites from mature rats following induction of LTP with theta-burst stimulation (TBS). Recent work suggests dendritic segments can act as functional units of plasticity. To test whether structural synaptic plasticity is similarly coordinated, we reconstructed from serial section transmission electron microscopy all of the spines and synapses along representative dendritic segments receiving control stimulation or TBS-LTP. At 5 min after TBS, polyribosomes were elevated in large spines suggesting an initial burst of local protein synthesis, and by 2 h only those spines with further enlarged synapses contained polyribosomes. Rapid induction of synaptogenesis was evidenced by an elevation in asymmetric shaft synapses and stubby spines at 5 min and more nonsynaptic filopodia at 30 min. By 2 h, the smallest synaptic spines were markedly reduced in number. This synapse loss was perfectly counterbalanced by enlargement of the remaining excitatory synapses such that the summed synaptic surface area per length of dendritic segment was constant across time and conditions. Remarkably, the inhibitory synapses showed a parallel synaptic plasticity, also demonstrating a decrease in number perfectly counterbalanced by an increase in synaptic surface area. Thus, TBS-LTP triggered spinogenesis followed by loss of small excitatory and inhibitory synapses and a subsequent enlargement of the remaining synapses by 2 h. These data suggest that dendritic segments coordinate structural plasticity across multiple synapses and maintain a homeostatic balance of excitatory and inhibitory inputs through local protein-synthesis and selective capture or redistribution of dendritic resources.
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Affiliation(s)
- Jennifer N Bourne
- Center for Learning and Memory, Section of Neurobiology, Institute for Neuroscience, University of Texas, Austin, Texas 78712, USA
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45
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Bourjaily MA, Miller P. Excitatory, inhibitory, and structural plasticity produce correlated connectivity in random networks trained to solve paired-stimulus tasks. Front Comput Neurosci 2011; 5:37. [PMID: 21991253 PMCID: PMC3170885 DOI: 10.3389/fncom.2011.00037] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 08/02/2011] [Indexed: 11/26/2022] Open
Abstract
The pattern of connections among cortical excitatory cells with overlapping arbors is non-random. In particular, correlations among connections produce clustering – cells in cliques connect to each other with high probability, but with lower probability to cells in other spatially intertwined cliques. In this study, we model initially randomly connected sparse recurrent networks of spiking neurons with random, overlapping inputs, to investigate what functional and structural synaptic plasticity mechanisms sculpt network connections into the patterns measured in vitro. Our Hebbian implementation of structural plasticity causes a removal of connections between uncorrelated excitatory cells, followed by their random replacement. To model a biconditional discrimination task, we stimulate the network via pairs (A + B, C + D, A + D, and C + B) of four inputs (A, B, C, and D). We find networks that produce neurons most responsive to specific paired inputs – a building block of computation and essential role for cortex – contain the excessive clustering of excitatory synaptic connections observed in cortical slices. The same networks produce the best performance in a behavioral readout of the networks’ ability to complete the task. A plasticity mechanism operating on inhibitory connections, long-term potentiation of inhibition, when combined with structural plasticity, indirectly enhances clustering of excitatory cells via excitatory connections. A rate-dependent (triplet) form of spike-timing-dependent plasticity (STDP) between excitatory cells is less effective and basic STDP is detrimental. Clustering also arises in networks stimulated with single stimuli and in networks undergoing raised levels of spontaneous activity when structural plasticity is combined with functional plasticity. In conclusion, spatially intertwined clusters or cliques of connected excitatory cells can arise via a Hebbian form of structural plasticity operating in initially randomly connected networks.
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Goold CP, Nicoll RA. Single-cell optogenetic excitation drives homeostatic synaptic depression. Neuron 2010; 68:512-28. [PMID: 21040851 DOI: 10.1016/j.neuron.2010.09.020] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/16/2010] [Indexed: 11/30/2022]
Abstract
Homeostatic processes have been proposed to explain the discrepancy between the dynamics of synaptic plasticity and the stability of brain function. Forms of synaptic plasticity such as long-term potentiation alter synaptic activity in a synapse- and cell-specific fashion. Although network-wide excitation triggers compensatory homeostatic changes, it is unknown whether neurons initiate homeostatic synaptic changes in response to cell-autonomous increases in excitation. Here we employ optogenetic tools to cell-autonomously excite CA1 pyramidal neurons and find that a compensatory postsynaptic depression of both AMPAR and NMDAR function results. Elevated calcium influx through L-type calcium channels leads to activation of a pathway involving CaM kinase kinase and CaM kinase 4 that induces synaptic depression of AMPAR and NMDAR responses. The synaptic depression of AMPARs but not of NMDARs requires protein synthesis and the GluA2 AMPAR subunit, indicating that downstream of CaM kinase activation divergent pathways regulate homeostatic AMPAR and NMDAR depression.
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Affiliation(s)
- Carleton P Goold
- Departments of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
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47
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Tetzlaff C, Okujeni S, Egert U, Wörgötter F, Butz M. Self-organized criticality in developing neuronal networks. PLoS Comput Biol 2010; 6:e1001013. [PMID: 21152008 PMCID: PMC2996321 DOI: 10.1371/journal.pcbi.1001013] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2010] [Accepted: 10/27/2010] [Indexed: 01/20/2023] Open
Abstract
Recently evidence has accumulated that many neural networks exhibit self-organized criticality. In this state, activity is similar across temporal scales and this is beneficial with respect to information flow. If subcritical, activity can die out, if supercritical epileptiform patterns may occur. Little is known about how developing networks will reach and stabilize criticality. Here we monitor the development between 13 and 95 days in vitro (DIV) of cortical cell cultures (n = 20) and find four different phases, related to their morphological maturation: An initial low-activity state (≈19 DIV) is followed by a supercritical (≈20 DIV) and then a subcritical one (≈36 DIV) until the network finally reaches stable criticality (≈58 DIV). Using network modeling and mathematical analysis we describe the dynamics of the emergent connectivity in such developing systems. Based on physiological observations, the synaptic development in the model is determined by the drive of the neurons to adjust their connectivity for reaching on average firing rate homeostasis. We predict a specific time course for the maturation of inhibition, with strong onset and delayed pruning, and that total synaptic connectivity should be strongly linked to the relative levels of excitation and inhibition. These results demonstrate that the interplay between activity and connectivity guides developing networks into criticality suggesting that this may be a generic and stable state of many networks in vivo and in vitro.
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Affiliation(s)
- Christian Tetzlaff
- Bernstein Center for Computational Neuroscience, Institute of Physics III - Biophysics, Georg-August Universität, Göttingen, Germany.
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48
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González‐Burgos I, García‐Martínez S, Velázquez‐Zamora D, Ponce‐Rolón R. Cytoarchitectural impairments in the medium spiny neurons of the
Nucleus Accumbens
core of hyperactive juvenile rats. Int J Dev Neurosci 2010; 28:475-80. [DOI: 10.1016/j.ijdevneu.2010.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/14/2010] [Accepted: 06/15/2010] [Indexed: 12/01/2022] Open
Affiliation(s)
- I. González‐Burgos
- División de NeurocienciasCentro de Investigación Biomédica de Occidente, IMSS.GuadalajaraJalMexico
- Departamento de Biología Celular y MolecularCUCBA, Universidad de GuadalajaraGuadalajaraJalMexico
| | - S. García‐Martínez
- División de NeurocienciasCentro de Investigación Biomédica de Occidente, IMSS.GuadalajaraJalMexico
| | - D.A. Velázquez‐Zamora
- División de NeurocienciasCentro de Investigación Biomédica de Occidente, IMSS.GuadalajaraJalMexico
- Departamento de Biología Celular y MolecularCUCBA, Universidad de GuadalajaraGuadalajaraJalMexico
| | - R. Ponce‐Rolón
- División de NeurocienciasCentro de Investigación Biomédica de Occidente, IMSS.GuadalajaraJalMexico
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Loss of GluN2B-containing NMDA receptors in CA1 hippocampus and cortex impairs long-term depression, reduces dendritic spine density, and disrupts learning. J Neurosci 2010; 30:4590-600. [PMID: 20357110 DOI: 10.1523/jneurosci.0640-10.2010] [Citation(s) in RCA: 261] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
NMDA receptors (NMDARs) are key mediators of certain forms of synaptic plasticity and learning. NMDAR complexes are heteromers composed of an obligatory GluN1 subunit and one or more GluN2 (GluN2A-GluN2D) subunits. Different subunits confer distinct physiological and molecular properties to NMDARs, but their contribution to synaptic plasticity and learning in the adult brain remains uncertain. Here, we generated mice lacking GluN2B in pyramidal neurons of cortex and CA1 subregion of hippocampus. We found that hippocampal principal neurons of adult GluN2B mutants had faster decaying NMDAR-mediated EPSCs than nonmutant controls and were insensitive to GluN2B but not NMDAR antagonism. A subsaturating form of hippocampal long-term potentiation (LTP) was impaired in the mutants, whereas a saturating form of LTP was intact. An NMDAR-dependent form of long-term depression (LTD) produced by low-frequency stimulation combined with glutamate transporter inhibition was abolished in the mutants. Additionally, mutants exhibited decreased dendritic spine density in CA1 hippocampal neurons compared with controls. On multiple assays for corticohippocampal-mediated learning and memory (hidden platform Morris water maze, T-maze spontaneous alternation, and pavlovian trace fear conditioning), mutants were impaired. These data further demonstrate the importance of GluN2B for synaptic plasticity in the adult hippocampus and suggest a particularly critical role in LTD, at least the form studied here. The finding that loss of GluN2B was sufficient to cause learning deficits illustrates the contribution of GluN2B-mediated forms of plasticity to memory formation, with implications for elucidating NMDAR-related dysfunction in disease-related cognitive impairment.
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50
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Brown CE, Boyd JD, Murphy TH. Longitudinal in vivo imaging reveals balanced and branch-specific remodeling of mature cortical pyramidal dendritic arbors after stroke. J Cereb Blood Flow Metab 2010; 30:783-91. [PMID: 19920846 PMCID: PMC2949167 DOI: 10.1038/jcbfm.2009.241] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The manner in which fully mature peri-infarct cortical dendritic arbors remodel after stroke, and thus may possibly contribute to stroke-induced changes in cortical receptive fields, is unknown. In this study, we used longitudinal in vivo two-photon imaging to investigate the extent to which brain ischemia can trigger dendritic remodeling of pyramidal neurons in the adult mouse somatosensory cortex, and to determine the nature by which remodeling proceeds over time and space. Before the induction of stroke, dendritic arbors were relatively stable over several weeks. However, after stroke, apical dendritic arbor remodeling increased significantly (dendritic tip growth and retraction), particularly within the first 2 weeks after stroke. Despite a threefold increase in structural remodeling, the net length of arbors did not change significantly over time because dendrite extensions away from the stroke were balanced by the shortening of tips near the infarct. Therefore, fully mature cortical pyramidal neurons retain the capacity for extensive structural plasticity and remodel in a balanced and branch-specific manner.
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Affiliation(s)
- Craig E Brown
- Department of Psychiatry, University of British Columbia, Vancouver, British Columbia, Canada.
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