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Neural Networks : the Official Journal... Jul 2020It was recently found that dendrites are not just a passive channel. They can perform mixed computation of analog and digital signals, and therefore can be abstracted as...
It was recently found that dendrites are not just a passive channel. They can perform mixed computation of analog and digital signals, and therefore can be abstracted as information processors. Moreover, dendrites possess a feedback mechanism. Motivated by these computational and feedback characteristics, this article proposes a new variant of neural-like P systems, dendrite P (DeP) systems, where neurons simulate the computational function of dendrites and perform a firing-storing process instead of the storing-firing process in spiking neural P (SNP) systems. Moreover, the behavior of the neurons is characterized by dendrite rules that are abstracted by two characteristics of dendrites. Different from the usual firing rules in SNP systems, the firing of a dendrite rule is controlled by the states of the corresponding source neurons. Therefore, DeP systems can provide a collaborative control capability for neurons. We discuss the computational power of DeP systems. In particular, it is proven that DeP systems are Turing-universal number generating/accepting devices. Moreover, we construct a small universal DeP system consisting of 115 neurons for computing functions.
Topics: Action Potentials; Dendrites; Humans; Models, Neurological; Neural Networks, Computer; Neurons; Synapses
PubMed: 32339806
DOI: 10.1016/j.neunet.2020.04.014 -
Scientific Reports Apr 2023With Hebbian learning 'who fires together wires together', well-known problems arise. Hebbian plasticity can cause unstable network dynamics and overwrite stored...
With Hebbian learning 'who fires together wires together', well-known problems arise. Hebbian plasticity can cause unstable network dynamics and overwrite stored memories. Because the known homeostatic plasticity mechanisms tend to be too slow to combat unstable dynamics, it has been proposed that plasticity must be highly gated and synaptic strengths limited. While solving the issue of stability, gating and limiting plasticity does not solve the stability-plasticity dilemma. We propose that dendrites enable both stable network dynamics and considerable synaptic changes, as they allow the gating of plasticity in a compartment-specific manner. We investigate how gating plasticity influences network stability in plastic balanced spiking networks of neurons with dendrites. We compare how different ways to gate plasticity, namely via modulating excitability, learning rate, and inhibition increase stability. We investigate how dendritic versus perisomatic gating allows for different amounts of weight changes in stable networks. We suggest that the compartmentalisation of pyramidal cells enables dendritic synaptic changes while maintaining stability. We show that the coupling between dendrite and soma is critical for the plasticity-stability trade-off. Finally, we show that spatially restricted plasticity additionally improves stability.
Topics: Dendrites; Neuronal Plasticity; Learning; Pyramidal Cells; Homeostasis; Action Potentials
PubMed: 37085642
DOI: 10.1038/s41598-023-32410-0 -
Seminars in Cell & Developmental Biology Sep 2022Precise neural networks, composed of axons and dendrites, are the structural basis for information processing in the brain. Therefore, the correct formation of neurites... (Review)
Review
Precise neural networks, composed of axons and dendrites, are the structural basis for information processing in the brain. Therefore, the correct formation of neurites is critical for accurate neural function. In particular, the three-dimensional structures of dendrites vary greatly among neuron types, and the unique shape of each dendrite is tightly linked to specific synaptic connections with innervating axons and is correlated with its information processing. Although many systems are involved in neurite formation, the developmental mechanisms that control the orientation, size, and arborization pattern of neurites definitively defines their three-dimensional structure in tissues. In this review, we summarize these regulatory mechanisms that establish proper spatial configurations of neurites, especially dendrites, in invertebrates and vertebrates.
Topics: Animals; Axons; Dendrites; Neurites; Neurogenesis; Neurons
PubMed: 35248463
DOI: 10.1016/j.semcdb.2022.02.015 -
Acta Neuropathologica Feb 2021Intellectual disability (ID) corresponds to several neurodevelopmental disorders of heterogeneous origin in which cognitive deficits are commonly associated with... (Review)
Review
Intellectual disability (ID) corresponds to several neurodevelopmental disorders of heterogeneous origin in which cognitive deficits are commonly associated with abnormalities of dendrites and dendritic spines. These histological changes in the brain serve as a proxy for underlying deficits in neuronal network connectivity, mostly a result of genetic factors. Historically, chromosomal abnormalities have been reported by conventional karyotyping, targeted fluorescence in situ hybridization (FISH), and chromosomal microarray analysis. More recently, cytogenomic mapping, whole-exome sequencing, and bioinformatic mining have led to the identification of novel candidate genes, including genes involved in neuritogenesis, dendrite maintenance, and synaptic plasticity. Greater understanding of the roles of these putative ID genes and their functional interactions might boost investigations into determining the plausible link between cellular and behavioral alterations as well as the mechanisms contributing to the cognitive impairment observed in ID. Genetic data combined with histological abnormalities, clinical presentation, and transgenic animal models provide support for the primacy of dysregulation in dendrite structure and function as the basis for the cognitive deficits observed in ID. In this review, we highlight the importance of dendrite pathophysiology in the etiologies of four prototypical ID syndromes, namely Down Syndrome (DS), Rett Syndrome (RTT), Digeorge Syndrome (DGS) and Fragile X Syndrome (FXS). Clinical characteristics of ID have also been reported in individuals with deletions in the long arm of chromosome 10 (the q26.2/q26.3), a region containing the gene for the collapsin response mediator protein 3 (CRMP3), also known as dihydropyrimidinase-related protein-4 (DRP-4, DPYSL4), which is involved in dendritogenesis. Following a discussion of clinical and genetic findings in these syndromes and their preclinical animal models, we lionize CRMP3/DPYSL4 as a novel candidate gene for ID that may be ripe for therapeutic intervention.
Topics: Animals; Child, Preschool; Chromosome Aberrations; Dendrites; Humans; Intellectual Disability; Nerve Tissue Proteins
PubMed: 33226471
DOI: 10.1007/s00401-020-02244-5 -
Current Opinion in Neurobiology Aug 2021Dendrite and axon arbors form scaffolds that connect a neuron to its partners; they are patterned to support the specific connectivity and computational requirements of... (Review)
Review
Dendrite and axon arbors form scaffolds that connect a neuron to its partners; they are patterned to support the specific connectivity and computational requirements of each neuron subtype. Transcription factor networks control the specification of neuron subtypes, and the consequent diversification of their stereotyped arbor patterns during differentiation. We outline how the differentiation trajectories of stereotyped arbors are shaped by hierarchical deployment of precursor cell and postmitotic transcription factors. These transcription factors exert modular control over the dendrite and axon features of a single neuron, create spatial and functional compartmentalization of an arbor, instruct implementation of developmental patterning rules, and exert operational control over the cell biological processes that construct an arbor.
Topics: Axons; Cell Differentiation; Dendrites; Neurons; Transcription Factors
PubMed: 33895620
DOI: 10.1016/j.conb.2021.03.013 -
The Journal of Neuroscience : the... Mar 2022Dendrite and axon arbor sizes are critical to neuronal function and vary widely between different neuron types. The relative dendrite and axon sizes of synaptic partners...
Dendrite and axon arbor sizes are critical to neuronal function and vary widely between different neuron types. The relative dendrite and axon sizes of synaptic partners control signal convergence and divergence in neural circuits. The developmental mechanisms that determine cell-type-specific dendrite and axon size and match synaptic partners' arbor territories remain obscure. Here, we discover that retinal horizontal cells express the leucine-rich repeat domain cell adhesion molecule AMIGO1. Horizontal cells provide pathway-specific feedback to photoreceptors-horizontal cell axons to rods and horizontal cell dendrites to cones. AMIGO1 selectively expands the size of horizontal cell axons. When is deleted in all or individual horizontal cells of either sex, their axon arbors shrink. By contrast, horizontal cell dendrites and synapse formation of horizontal cell axons and dendrites are unaffected by AMIGO1 removal. The dendrites of rod bipolar cells, which do not express AMIGO1, shrink in parallel with horizontal cell axons in () mice. This territory matching maintains the function of the rod bipolar pathway, preserving bipolar cell responses and retinal output signals in mice. We previously identified AMIGO2 as a scaling factor that constrains retinal neurite arbors. Our current results identify AMIGO1 as a scaling factor that expands retinal neurite arbors and reveal territory matching as a novel homeostatic mechanism. Territory matching interacts with other homeostatic mechanisms to stabilize the development of the rod bipolar pathway, which mediates vision near the threshold. Neurons send and receive signals through branched axonal and dendritic arbors. The size of these arbors is critical to the function of a neuron. Axons and dendrites grow during development and are stable at maturity. The mechanisms that determine axon and dendrite size are not well understood. Here, we identify a cell surface protein, AMIGO1, that selectively promotes axon growth of horizontal cells, a retinal interneuron. Removal of AMIGO1 reduces the size of horizontal cell axons without affecting the size of their dendrites or the ability of both arbors to form connections. The changes in horizontal cell axons are matched by changes in synaptic partner dendrites to stabilize retinal function. This identifies territory matching as a novel homeostatic plasticity mechanism.
Topics: Animals; Axons; Dendrites; Mice; Retina; Retinal Bipolar Cells; Retinal Cone Photoreceptor Cells
PubMed: 35169021
DOI: 10.1523/JNEUROSCI.1164-21.2022 -
Neuron May 2020Dendrite arbor pattern determines the functional characteristics of a neuron. It is founded on primary branch structure, defined through cell intrinsic and...
Dendrite arbor pattern determines the functional characteristics of a neuron. It is founded on primary branch structure, defined through cell intrinsic and transcription-factor-encoded mechanisms. Developing arbors have extensive acentrosomal microtubule dynamics, and here, we report an unexpected role for the atypical actin motor Myo6 in creating primary branch structure by specifying the position, polarity, and targeting of these events. We carried out in vivo time-lapse imaging of Drosophila adult sensory neuron differentiation, integrating machine-learning-based quantification of arbor patterning with molecular-level tracking of cytoskeletal remodeling. This revealed that Myo6 and the transcription factor Knot regulate transient surges of microtubule polymerization at dendrite tips; they drive retrograde extension of an actin filament array that specifies anterograde microtubule polymerization and guides these microtubules to subdivide the tip into multiple branches. Primary branches delineate functional compartments; this tunable branching mechanism is key to define and diversify dendrite arbor compartmentalization.
Topics: Animals; Cell Line; Cells, Cultured; Dendrites; Drosophila Proteins; Drosophila melanogaster; Microtubules; Myosin Heavy Chains; Neurogenesis; Transcription Factors
PubMed: 32155441
DOI: 10.1016/j.neuron.2020.02.002 -
Developmental Biology Aug 2022Axon regeneration in response to injury has been documented in many animals over several hundred years. In contrast, how neurons respond to dendrite injury has been...
Axon regeneration in response to injury has been documented in many animals over several hundred years. In contrast, how neurons respond to dendrite injury has been examined only in the last decade. So far, dendrite regeneration after injury has been documented in invertebrate model systems, but has not been assayed in a vertebrate. In this study, we use zebrafish motor neurons to track neurons after dendrite injury. We address two major gaps in our knowledge of dendrite regeneration: 1) whether post-synaptic dendrites can regenerate and 2) whether vertebrate dendrites can regenerate. We find that motor neurons survive laser microsurgery to remove one or all dendrites. Outgrowth of new dendrites typically initiated one to three days after injury, and a new, stable dendrite arbor was in place by five days after injury. We conclude that zebrafish motor neurons have the capacity to regenerate a new dendrite arbor.
Topics: Animals; Axons; Dendrites; Motor Neurons; Nerve Regeneration; Spinal Cord; Spinal Cord Regeneration; Zebrafish
PubMed: 35644253
DOI: 10.1016/j.ydbio.2022.05.014 -
Neuroscience May 2022Much of our understanding of dendritic and synaptic physiology comes from in vitro experimentation, where the afforded mechanical stability and convenience of applying... (Review)
Review
Much of our understanding of dendritic and synaptic physiology comes from in vitro experimentation, where the afforded mechanical stability and convenience of applying drugs allowed patch-clamping based recording techniques to investigate ion channel distributions, their gating kinetics, and to uncover dendritic integrative and synaptic plasticity rules. However, with current efforts to study these questions in vivo, there is a great need to translate existing knowledge between in vitro and in vivo experimental conditions. In this review, we identify discrepancies between in vitro and in vivo ionic composition of extracellular media and discuss how changes in ionic composition alter dendritic excitability and plasticity induction. Here, we argue that under physiological in vivo ionic conditions, dendrites are expected to be more excitable and the threshold for synaptic plasticity induction to be lowered. Consequently, the plasticity rules described in vitro vary significantly from those implemented in vivo.
Topics: Action Potentials; Dendrites; Ion Channels; Neuronal Plasticity; Synapses
PubMed: 34998890
DOI: 10.1016/j.neuroscience.2021.12.039 -
Cell Reports Apr 2022Neuronal morphologies provide the foundation for the electrical behavior of neurons, the connectomes they form, and the dynamical properties of the brain. Comprehensive...
Neuronal morphologies provide the foundation for the electrical behavior of neurons, the connectomes they form, and the dynamical properties of the brain. Comprehensive neuron models are essential for defining cell types, discerning their functional roles, and investigating brain-disease-related dendritic alterations. However, a lack of understanding of the principles underlying neuron morphologies has hindered attempts to computationally synthesize morphologies for decades. We introduce a synthesis algorithm based on a topological descriptor of neurons, which enables the rapid digital reconstruction of entire brain regions from few reference cells. This topology-guided synthesis generates dendrites that are statistically similar to biological reconstructions in terms of morpho-electrical and connectivity properties and offers a significant opportunity to investigate the links between neuronal morphology and brain function across different spatiotemporal scales. Synthesized cortical networks based on structurally altered dendrites associated with diverse brain pathologies revealed principles linking branching properties to the structure of large-scale networks.
Topics: Algorithms; Brain; Connectome; Dendrites; Neurons
PubMed: 35385736
DOI: 10.1016/j.celrep.2022.110586