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نتیجه جستجو - Neuronal networks

تعداد مقالات یافته شده: 8
ردیف عنوان نوع
1 Graph-theoretical derivation of brain structural connectivity
استخراج نمودار نظری از اتصال ساختاری مغز-2020
Brain connectivity at the single neuron level can provide fundamental insights into how information is integrated and propagated within and between brain regions. However, it is almost impossible to adequately study this problem experimentally and, despite intense ef- forts in the field, no mathematical description has been obtained so far. Here, we present a mathematical framework based on a graph-theoretical approach that, starting from exper- imental data obtained from a few small subsets of neurons, can quantitatively explain and predict the corresponding full network properties. This model also changes the paradigm with which large-scale model networks can be built, from using probabilistic/empiric con- nections or limited data, to a process that can algorithmically generate neuronal networks connected as in the real system.
Keywords: Connectome | Neuronal networks | Random graphs
مقاله انگلیسی
2 Short-term neuronal effects of Fumonisin B1 on neuronal activity in rodents
اثرات عصبی کوتاه مدت Fumonisin B1 بر فعالیت عصبی در جوندگان-2020
Fumonisin B1 (FB1) is a mycotoxin produced by microscopic fungi (mostly Fusarium species), which may infect our major crops. The toxin inhibits the development of these plants and may also have harmful effects on animals and humans consuming the infected crops. FB1 inhibits sphingolipid biosynthesis which leads to altered membrane characteristics and consequently, altered cellular functions. There are some indications that the toxin has inhibitory effects on neuronal activity in case of repeated consumption, presumably due to sphingolipid depletion. However, according to new literature data, FB1 may have acute excitatory neural effects, too, via different mechanisms of action. Therefore, in the present study, we addressed the neuronal network effects of FB1 following acute treatment, using different electrophysiological techniques in vitro and in vivo. Acute treatments with FB1 (10-100 μM) were carried out on brain slices, tissue cultures and live animals. After direct treatment of samples, electrically evoked or spontaneous field potentials were examined in the hippocampus and the neocortex of rat brain slices and in hippocampal cell cultures. In the hippocampus, a short-term increase in the excitability of neuronal networks and individual cells was observed in response to FB1 treatment. In some cases, the initially enhanced excitation was reversed presumably due to overactivation of neuronal networks. Normal spontaneous activity was found to be stimulated in hippocampal cell cultures. Seizure susceptibility was not affected in the neocortex of brain slices. For the verification of the results caused by direct treatment, effects of systemic administration of FB1 (7.5 mg/kg, i.p.) were also examined. Evoked field potentials recorded in vivo from the somatosensory cortex and cell activation measured by the c-fos technique in hippocampus and somatosensory cortex were analyzed. However, the hippocampal and cortical stimulatory effect detected in vitro could not be demonstrated by these in vivo assays. Altogether, the toxin enhanced the basic excitability of neurons and neuronal networks after direct treatment but there were no effects on the given brain areas after systemic treatment in vivo. Based on the observed in vitro FB1 effects and the lack of data on the penetration of FB1 across the blood-brain barrier, we assume that in vivo consequences of FB1 administration can be more prominent in case of perturbed blood-brain barrier functions.
Keywords: neurotoxicity | electrophysiology | c-Fos, mycotoxin | field potential | brain slice | tissue culture
مقاله انگلیسی
3 Effects of electromagnetic induction on vibrational resonance in single neurons and neuronal networks
اثرات القایی الکترومغناطیسی بر تشدید ارتعاش در سلولهای عصبی تنها و شبکه های عصبی-2020
In this paper, Vibrational Resonance (VR), in which the response of some dynamical systems to a weak, low frequency signal can be enhanced by the optimal amplitude of high frequency signal, is investigated under the effects of electromagnetic induction in both single neurons and small-world networks. We find that the occurrence of VR in single neurons requires less energy in the presence of electromagnetic induction, although the resonant peak of the response reduces. Besides, VR can be obtained in small-world networks both with and without electromagnetic induction. In small-world neuronal networks, the highest resonance peak of VR enhances with an increase in the probability of adding link in case of without electromagnetic induction. On the other hand, with the increasing of the probability of adding link, VR disappears in the presence of relatively strong electromagnetic induction, while it enhances in the presence of relatively weak electromagnetic induction
Keywords: Electromagnetic induction | Vibrational resonance | Hodgkin–Huxley neuron
مقاله انگلیسی
4 Sparsity through evolutionary pruning prevents neuronal networks from overfitting
Sparsity از طریق هرس تکاملی شبکه های عصبی جلوگیری می از Over-fitting-2020
Modern Machine learning techniques take advantage of the exponentially rising calculation power in new generation processor units. Thus, the number of parameters which are trained to solve complex tasks was highly increased over the last decades. However, still the networks fail – in contrast to our brain – to develop general intelligence in the sense of being able to solve several complex tasks with only one network architecture. This could be the case because the brain is not a randomly initialized neural network, which has to be trained from scratch by simply investing a lot of calculation power, but has from birth some fixed hierarchical structure. To make progress in decoding the structural basis of biological neural networks we here chose a bottom-up approach, where we evolutionarily trained small neural networks in performing a maze task. This simple maze task requires dynamic decision making with delayed rewards. We were able to show that during the evolutionary optimization random severance of connections leads to better generalization performance of the networks compared to fully connected networks. We conclude that sparsity is a cent
Keywords: Evolution | Artificial neural networks | Maze task | Evolutionary algorithm | Overfitting | Biological plausibility
مقاله انگلیسی
5 Time delayed chemical synapses and synchronization in multilayer neuronal networks with ephaptic inter-layer coupling
تأخیر زمان در سیناپسهای شیمیایی و هماهنگ سازی در شبکه های عصبی چند لایه با اتصال بین لایه ای ephaptic -2020
In this paper, a three-layer neuronal network is studied to consider different com plex con- nections between the neurons. In the nervous system, the communication between the neurons is mostly based on the electrical and chemical synapses. However, extracellular electric fields can induce a magnetic flux which can lead to indirect neural communica- tions, by means of electromagnetic induction. This mode of coupling is called ephaptic coupling, which here is used between the layer. To describe the coupling within the lay- ers, the electrical and chemical synapses are defined. We also take into account the par- tial time delays, to reflect the required time for information transmission through chem- ical synapses. Particularly, we consider partial and full time delays, as well as strong and weak coupling strengths. It is shown that three layers typically have opposite synchroniza- tion properties in the strong and weak coupling regimes. Specifically, when the coupling is strong, the top and bottom layers are synchronous, while the middle layer is desyn- chronous. But when the coupling is weak, the middle layer is synchronous, while the top and bottom layers are desynchronous. In overall, the most synchrony is obtained when the weak coupling is accompanied with partial time delays in chemical communications. Our research sheds new light on the complex interplay between the time delay, the ephaptic coupling, and the synchronization in neuronal networks.
Keywords: Multilayer network | Ephaptic coupling | Time delay | Synchronization
مقاله انگلیسی
6 Long-Range Optogenetic Control of Axon Guidance Overcomes Developmental Boundaries and Defects
کنترل بینایی زاویه دار راهنمایی آکسون بر مرزها و نقص های توسعه غلبه می کند-2020
Axons connect neurons together, establishing the wiring architecture of neuronal networks. Axonal connectivity is largely built during embryonic development through highly constrained processes of axon guidance, which have been extensively studied. However, the inability to control axon guidance, and thus neuronal network architecture, has limited investigation of how axonal connections influence subsequent development and function of neuronal networks. Here, weuse zebrafish motor neurons expressing a photoactivatable Rac1 to co-opt endogenous growth cone guidance machinery to precisely and non-invasively direct axon growth using light. Axons can be guided over large distances, within complex environments of living organisms, overriding competing endogenous signals and redirecting axons across potent repulsive barriers to construct novel circuitry. Notably, genetic axon guidance defects can be rescued, restoring functional connectivity. These data demonstrate that intrinsic growth cone guidance machinery can be co-opted to non-invasively build new connectivity, allowing investigation of neural network dynamics in intact living organisms.
مقاله انگلیسی
7 Distinct Pathogenic Genes Causing Intellectual Disability and Autism Exhibit a Common Neuronal Network Hyperactivity Phenotype
ژنهای پاتوژن مشخص متمایز کننده ناتوانی ذهنی و اوتیسم از فنوتیپ بیش فعالی شبکه عصبی مشترک-2020
Pathogenic mutations in either one of the epigenetic modifiers EHMT1, MBD5, MLL3, or SMARCB1 have been identified to be causative for Kleefstra syndrome spectrum (KSS), a neurodevelopmental disorder with clinical features of both intellectual disability (ID) and autism spectrum disorder (ASD). To understand how these variants lead to the phenotypic convergence in KSS, we employ a loss-of-function approach to assess neuronal network development at the molecular, single-cell, and network activity level. KSS-gene-deficient neuronal networks all develop into hyperactive networks with altered network organization and excitatory-inhibitory balance. Interestingly, even though transcriptional data reveal distinct regulatory mechanisms, KSS target genes share similar functions in regulating neuronal excitability and synaptic function, several of which are associated with ID and ASD. Our results show that KSS genes mainly converge at the level of neuronal network communication, providing insights into the pathophysiology of KSS and phenotypically congruent disorders.
مقاله انگلیسی
8 m:3243A > G-Induced Mitochondrial Dysfunction Impairs Human Neuronal Development and Reduces Neuronal Network Activity and Synchronicity
m:3243A > G-Induced Mitochondrial Dysfunction Impairs Human Neuronal Development and Reduces Neuronal Network Activity and Synchronicity-2020
Epilepsy, intellectual and cortical sensory deficits, and psychiatric manifestations are the most frequent manifestations of mitochondrial diseases. How mitochondrial dysfunction affects neural structure and function remains elusive, mostly because of a lack of proper in vitro neuronal model systems with mitochondrial dysfunction. Leveraging induced pluripotent stem cell technology, we differentiated excitatory cortical neurons (iNeurons) with normal (low heteroplasmy) and impaired (high heteroplasmy) mitochondrial function on an isogenic nuclear DNA background from patients with the common pathogenic m.3243A > G variant of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). iNeurons with high heteroplasmy exhibited mitochondrial dysfunction, delayed neural maturation, reduced dendritic complexity, and fewer excitatory synapses. Micro-electrode array recordings of neuronal networks displayed reduced network activity and decreased synchronous network bursting. Impaired neuronal energy metabolism and compromised structural and functional integrity of neurons and neural networks could be the primary drivers of increased susceptibility to neuropsychiatric manifestations of mitochondrial disease.
مقاله انگلیسی
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