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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 |
Self-reorganization of neuronal activation patterns in the cortexunder brain-machine interface and neural operant conditioning
خود سازماندهی مجدد الگوهای فعال سازی عصبی در رابط دستگاه مغز قشر مغز و تهویه عمل عصبی-2020 In this review, we describe recent experimental observations and model simulations in the research sub-ject of brain-machine interface (BMI). Studies of BMIs have applied decoding models to extract functionalcharacteristics of the recorded neurons, and some of these have more focused on adaptation based onneural operant conditioning. Under a closed loop feedback with the environment through BMIs, neuronalactivities are forced to interact directly with the environment. These studies have shown that the neuronensembles self-reorganized their activity patterns and completed a transition to adaptive state within ashort time scale. Based on these observations, we discuss how the brain could identify the target neu-rons directly interacting with the environment and determine in which direction the activities of thoseneurons should be changed for adaptation. For adaptation over a short time scale, the changes of neuronensemble activities seem to be restricted by the intrinsic correlation structure of the neuronal network(intrinsic manifold). On the other hand, for adaptation over a long time scale, modifications to the synapticconnections enable the neuronal network to generate a novel activation pattern required by BMI (exten-sion of the intrinsic manifold). Understanding of the intrinsic constraints in adaptive changes of neuronalactivities will provide the basic principles of learning mechanisms in the brain and methodological cluesfor better performance in engineering and clinical applications of BMI. Keywords:Oscillology | Brain-machine Interface | Neural operant conditioning | BMI | Intrinsic manifold |
مقاله انگلیسی |
4 |
Spontaneous T. gondii neuronal encystment induces structural neuritic network impairment associated with changes of tyrosine hydroxilase expression
رمزگذاری عصبی T. gondii خودبخودی باعث اختلال در ساختار شبکه عصبی ناشی از تغییرات بیان هیدروکسیلاز تیروزین-2020 Two billion people are chronically infected with Toxoplasma gondii worldwide with unknown consequences.
Important neurological diseases have been associated to the brain infection, making essential to understand the
neurophysiological changes associated with the neuronal encystment. T. gondii may subvert neuronal functions
modifying neurotransmitter concentration in chronically infected mice but the molecular mechanisms involved
are still unclear. Parasites were observed inside neuronal cells in cultures from 24−192 hs. The rate of infection
increased with time. Neurite density decreased affecting network functionality. Neuronal survival was affected
and we detected the presence of cysts inside neuronal bodies and dilated portions of neurites in association with
a relative increase of TH-positive neuritic area without noticeable changes in DA immunofluorescence pattern.
These results advance our knowledge of the interaction between T. gondii and the neuronal network of the host. Keywords: Toxoplasma gondii | Cystogenesis | Tyrosine hydroxylase | Dopamine | Primary neuron culture | Superior cervical ganglion |
مقاله انگلیسی |
5 |
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 |
6 |
Nutritional control of puberty in the bovine female: prenatal and early postnatal regulation of the neuroendocrine system
کنترل تغذیه ای بلوغ در گاو های ماده : تنظیم پیش از تولد و زودرس پس از زایمان سیستم عصبی و غدد درونریز-2020 Puberty is a complex biological event that requires maturation of the reproductive
neuroendocrine axis and subsequent initiation of high-frequency, episodic release of GnRH
and LH. Nutrition is a critical factor affecting the neuroendocrine control of puberty.
Although nutrient restriction during juvenile development delays puberty, elevated rates
of body weight gain during this period facilitate pubertal maturation by programming
hypothalamic centers that underlie the pubertal process. Recent findings suggest that
maternal nutrition during gestation can also modulate the development of the fetal
neuroendocrine axis, thus influencing puberty and subsequent reproductive function.
Among the several metabolic signals, leptin plays a critical role in conveying metabolic
information to the brain and, consequently, controlling puberty. The effects of leptin on
GnRH secretion are mediated via an upstream neuronal network because GnRH neurons
do not express the leptin receptor. Two neuronal populations located in the arcuate nucleus
that express the orexigenic peptide neuropeptide Y (NPY), and the anorexigenic
peptide alpha melanocyte-stimulating hormone (aMSH), are key components of the
neurocircuitry that conveys inhibitory (NPY) and excitatory (aMSH) inputs to GnRH neurons.
In addition, neurons in the arcuate nucleus that coexpress kisspeptin, neurokinin B,
and dynorphin (termed KNDy neurons) are also involved in the metabolic control of puberty.
Our studies in the bovine female demonstrate that increased planes of nutrition
during juvenile development lead to organizational and functional changes in hypothalamic
pathways comprising NPY, proopiomelanocortin (POMC, the precursor of aMSH),
and kisspeptin neurons. Changes include alterations in the abundance of NPY, POMC, and
Kiss1 mRNA and in plasticity of the neuronal projections to GnRH neurons. Our studies also
indicate that epigenetic mechanisms, such as modifications in the DNA methylation
pattern, are involved in this process. Finally, our most recent data demonstrate that
maternal nutrition during gestation can also induce morphological and functional changes
in the hypothalamic NPY system in the heifer offspring that are likely to persist long after
birth. These organizational changes occurring during fetal development have the potential
to not only impact puberty but also influence reproductive performance throughout
adulthood in the bovine female. Keywords: Heifers | Hypothalamus | Leptin | Nutrition | Puberty |
مقاله انگلیسی |
7 |
Cuneate spiking neural network learning to classify naturalistic texture stimuli under varying sensing conditions
یادگیری شبکه عصبی اسپایک کانیت برای طبقه بندی محرکهای بافت طبیعی در شرایط مختلف سنجش-2020 We implemented a functional neuronal network that was able to learn and discriminate haptic features
from biomimetic tactile sensor inputs using a two-layer spiking neuron model and homeostatic
synaptic learning mechanism. The first order neuron model was used to emulate biological tactile
afferents and the second order neuron model was used to emulate biological cuneate neurons. We have
evaluated 10 naturalistic textures using a passive touch protocol, under varying sensing conditions.
Tactile sensor data acquired with five textures under five sensing conditions were used for a synaptic
learning process, to tune the synaptic weights between tactile afferents and cuneate neurons. Using
post-learning synaptic weights, we evaluated the individual and population cuneate neuron responses
by decoding across 10 stimuli, under varying sensing conditions. This resulted in a high decoding
performance. We further validated the decoding performance across stimuli, irrespective of sensing
velocities using a set of 25 cuneate neuron responses. This resulted in a median decoding performance
of 96% across the set of cuneate neurons. Being able to learn and perform generalized discrimination
across tactile stimuli, makes this functional spiking tactile system effective and suitable for further
robotic applications. Keywords: Spiking neural network | Neurorobotics | Cuneate neurons | Primary afferents | Tactile sensing | Synaptic weight learning |
مقاله انگلیسی |
8 |
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 |
9 |
Chimeras in an adaptive neuronal network with burst-timing-dependent plasticity
Chimeras در یک شبکه عصبی سازگار با انعطاف پذیری وابسته به زمان-2020 The synchronized behavior of neurons depends on the structure and function of the synaptic connec- tions between them. One of the activity-dependent synaptic modifications is the burst-timing-dependent plasticity, which relies on the latencies of the presynaptic and postsynaptic bursts. In this paper, we, therefore, study the collective behavior of a neuronal network with burst-timing-dependent plasticity, in particular, focusing on the emergence of chimera states. We consider separately non-local and global couplings, which have substantial effects on the collective dynamics. We show that the considered burst- timing-dependent plasticity leads to different behavior from static networks. The histogram of the synap- tic strengths, in particular, reveals a different evolution of the chimera states in comparison to the devel- opment of synchronous and asynchronous states. Keywords: Chimera state | Neuronal network | Adaptive coupling | Burst-timing-dependent plasticity |
مقاله انگلیسی |
10 |
A self-assembled layer-by-layer surface modification to fabricate the neuron-rich model from neural stem/precursor cells
اصلاح سطح لایه به لایه خود مونتاژ برای ساخت مدل غنی از نورون از سلولهای بنیادی / پیش ساز عصبی-2020 Background/Purpose: In vitro neural cell-based models have been widely used to mimic the
in vivo neural tissue environments and quantitatively understand the effects of pharmaceutical
molecules on neural diseases. Recently, several biomimetic neural tissue models have
been widely developed by using biomaterials or surface modification. However, the complex
protocols of material synthesis or surface modification lack an easy execution to fabricate
the neuron favorite environment.
Methods: In this study, we utilized a layer-by-layer technique as a surface modification method
for regulating the behaviors of neural stem/precursor cells (NSPCs) on material surfaces. Polyelectrolyte
multilayers (PEMs) via alternate deposition of poly (allylamine hydrochloride) (PAH)
and poly (sodium-4-styrenesulfonate) (PSS) were used to culture NSPCs. After incubation for 7
days, the neuronal differentiation of NSPCs and synapse function of differentiated neurons
were identified by immunocytochemistry for lineage specific markers.
Results: Compared with the only PAH film, the PSS-ending film (neuron-rich model) was
shown to significantly promote differentiation of NSPCs into neurons (more than 50%), form
a neuronal network structure; and differentiated neurons exhibiting functional synaptic
activity. KEYWORDS : Polyelectrolyte multilayer (PEM) | Neural stem/ precursor cells | (NSPCs) | Neuronal | differentiation | Neurite outgrowth |
مقاله انگلیسی |