Littérature scientifique sur le sujet « Neuroni corticali »
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Articles de revues sur le sujet "Neuroni corticali"
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Masuda, Naoki, et Kazuyuki Aihara. « Spatiotemporal Spike Encoding of a Continuous External Signal ». Neural Computation 14, no 7 (1 juillet 2002) : 1599–628. http://dx.doi.org/10.1162/08997660260028638.
Texte intégralRésumé :
Interspike intervals of spikes emitted from an integrator neuron model of sensory neurons can encode input information represented as a continuous signal from a deterministic system. If a real brain uses spike timing as a means of information processing, other neurons receiving spatiotemporal spikes from such sensory neurons must also be capable of treating information included in deterministic interspike intervals. In this article, we examine functions of neurons modeling cortical neurons receiving spatiotemporal spikes from many sensory neurons. We show that such neuron models can encode stimulus information passed from the sensory model neurons in the form of interspike intervals. Each sensory neuron connected to the cortical neuron contributes equally to the information collection by the cortical neuron. Although the incident spike train to the cortical neuron is a superimposition of spike trains from many sensory neurons, it need not be decomposed into spike trains according to the input neurons. These results are also preserved for generalizations of sensory neurons such as a small amount of leak, noise, inhomogeneity in firing rates, or biases introduced in the phase distributions.
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Zhou, Xiaoming, et Philip H. S. Jen. « Corticofugal Modulation of Multi-Parametric Auditory Selectivity in the Midbrain of the Big Brown Bat ». Journal of Neurophysiology 98, no 5 (novembre 2007) : 2509–16. http://dx.doi.org/10.1152/jn.00613.2007.
Texte intégralRésumé :
Corticofugal modulation of sub-cortical auditory selectivity has been shown previously in mammals for frequency, amplitude, time, and direction domains in separate studies. As such, these studies do not show if multi-parametric corticofugal modulation can be mediated through the same sub-cortical neuron. Here we specifically studied corticofugal modulation of best frequency (BF), best amplitude (BA), and best azimuth (BAZ) at the same neuron in the inferior colliculus of the big brown bat, Eptesicus fuscus, using focal electrical stimulation in the auditory cortex. Among 53 corticofugally inhibited collicular neurons examined, cortical electrical stimulation produced a shift of all three measurements (i.e., BF, BA, and BAZ) toward the value of stimulated cortical neuron in 13 (24.5%) neurons, two measurements (i.e., BF and BAZ or BA and BAZ) in 19 (36%) neurons, and one measurement in 16 (30%) neurons. Cortical electrical stimulation did not shift any of these measurements in the remaining five (9.5%) neurons. Corticofugally induced collicular BF shift was symmetrical, whereas the shift in collicular BA or BAZ was asymmetrical. The amount of shift in each measurement was significantly correlated with each measurement difference between recorded collicular and stimulated cortical neurons. However, shifts of three measurements were not correlated with each other. Furthermore, average measurement difference between collicular and cortical neurons was larger for collicular neurons with measurement shifts than for those without shifts. These data indicate that multi-parametric corticofugal modulation can be mediated through the same subcortical neuron based on the difference in auditory selectivity between subcortical and cortical neurons.
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Wright, Nathaniel C., Mahmood S. Hoseini, Tansel Baran Yasar et Ralf Wessel. « Coupling of synaptic inputs to local cortical activity differs among neurons and adapts after stimulus onset ». Journal of Neurophysiology 118, no 6 (1 décembre 2017) : 3345–59. http://dx.doi.org/10.1152/jn.00398.2017.
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Cortical activity contributes significantly to the high variability of sensory responses of interconnected pyramidal neurons, which has crucial implications for sensory coding. Yet, largely because of technical limitations of in vivo intracellular recordings, the coupling of a pyramidal neuron’s synaptic inputs to the local cortical activity has evaded full understanding. Here we obtained excitatory synaptic conductance ( g) measurements from putative pyramidal neurons and local field potential (LFP) recordings from adjacent cortical circuits during visual processing in the turtle whole brain ex vivo preparation. We found a range of g-LFP coupling across neurons. Importantly, for a given neuron, g-LFP coupling increased at stimulus onset and then relaxed toward intermediate values during continued visual stimulation. A model network with clustered connectivity and synaptic depression reproduced both the diversity and the dynamics of g-LFP coupling. In conclusion, these results establish a rich dependence of single-neuron responses on anatomical, synaptic, and emergent network properties. NEW & NOTEWORTHY Cortical neurons are strongly influenced by the networks in which they are embedded. To understand sensory processing, we must identify the nature of this influence and its underlying mechanisms. Here we investigate synaptic inputs to cortical neurons, and the nearby local field potential, during visual processing. We find a range of neuron-to-network coupling across cortical neurons. This coupling is dynamically modulated during visual processing via biophysical and emergent network properties.
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Alloway, K. D., M. J. Johnson et M. B. Wallace. « Thalamocortical interactions in the somatosensory system : interpretations of latency and cross-correlation analyses ». Journal of Neurophysiology 70, no 3 (1 septembre 1993) : 892–908. http://dx.doi.org/10.1152/jn.1993.70.3.892.
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1. Isolated extracellular neuronal responses to cutaneous stimulation were simultaneously recorded from corresponding peripheral representations in the ventrobasal nucleus and primary somatosensory cortex of intact, halothane-anesthetized rats. Thalamic and cortical neurons representing hairy skin on the forelimb were activated by hair movements produced by a series of 50 or 100 discrete air jets. A corresponding set of neurons representing the glabrous pads of the hind paw were activated by a similar number of punctate mechanical displacements. 2. Cortical electrode penetrations were histologically reconstructed, and 118 neurons in the glabrous skin representation exhibited cutaneous responses that were categorized into supragranular, granular, or infragranular groups according to their laminar position. Minimum latencies of cortical neurons responding to glabrous skin displacement were analyzed, and significant differences were found in the distribution of minimum latencies for the different cortical layers. Mean values for minimum latencies in the infragranular and granular layers were 15.8 and 16.3 ms, respectively, whereas supragranular neurons were characterized by minimum latencies having a mean of 20 ms. The differences between these groups suggests that stimulus-induced afferent activity reaches infragranular and granular layers before contacting supragranular neurons. Average latencies were also calculated on responses occurring during the 1st 20 trials, but the cortical distributions of these values overlapped considerably, and differences between the laminar groups were not statistically significant. 3. In several recording sites, two cortical neurons were recorded simultaneously, and the response latencies of these matched pairs were often substantially different despite the similarity in laminar position. This result indicates that laminar location is not the only determinant of response latency and that serially organized circuits are distributed within, as well as between, cortical layers. 4. From a sample of 302 neurons exhibiting cutaneous responses within histologically identified regions of thalamus or cortex, a set of 143 pairs of neurons recorded simultaneously from both regions was available for cross-correlation analysis. Significant thalamocortical interactions were found in 38 neurons pairs. Analysis of these significant interactions revealed that thalamocortical connection strength, as measured by neuronal efficacy, was two to four times larger for neuron pairs having the cortical cell in granular layer IV than for neuron pairs having an extragranular layer cortical neuron. There was no difference in thalamocortical connection strength between neuron pairs containing supra- or infragranular cortical neurons. 5. Summed peristimulus time histograms revealed stimulus-locked inhibition of spontaneous activity in 4% (8/195) or cortical and 18% (20/107) of thalamic neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Yamamoto, T., N. Yuyama, T. Kato et Y. Kawamura. « Gustatory responses of cortical neurons in rats. II. Information processing of taste quality ». Journal of Neurophysiology 53, no 6 (1 juin 1985) : 1356–69. http://dx.doi.org/10.1152/jn.1985.53.6.1356.
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The present report was designed to investigate neural coding of taste information in the cerebral cortical taste area of rats. The magnitude and/or type (excitatory, inhibitory, or no-response) of responses of 111 cortical neurons evoked by single concentrations of the four basic taste stimuli (sucrose, NaCl, HCl, and quinine HCl) were subjected to four types of analyses in the context of the four proposed hypotheses of taste-quality coding: across-neuron response-pattern, labeled-line, matrix-pattern, and across-region response-pattern notions (88 histologically located neurons). An across-neuron response-pattern notion assumes that taste quality is coded by differential magnitudes of response across many neurons. This theory utilizes across-neuron correlation coefficients as a metric for the evaluation of taste quality coding. Across-neuron correlations between magnitudes of responses to any pairs of the four basic taste stimuli across 111 cortical neurons were very high and were similar. However, calculations made with net responses (spontaneous rate subtracted) resulted in less positive correlations but still similar values among the various pairs of taste stimuli. This finding suggests that across-neuron response patterns of cortical neurons become less discriminating among taste qualities compared with those of the lower-order neurons. A labeled-line notion assumes that there are identifiable groups of neurons and that taste quality is coded by activity in these particular sets of neurons. Some investigators have classified taste-responsive neurons into best-stimulus categories, depending on their best sensitivity to any one of the four basic stimuli, such as sucrose-best, NaCl-best, HCl-best, and quinine-best neurons; they have suggested that taste can be classified along four qualitative dimensions that correspond to these four neuron types (i.e., four labeled lines). The present study shows that responsiveness of each of the four best-stimulus neurons had similar profiles between peripheral and cortical levels. That is, when the stimuli were arranged along the abscissa in the order of sucrose, NaCl, HCl, and quinine, there is a peak response in one place, and the responses decreased gradually from the peak. However, such response characteristics do not favor the labeled-line theory, since they can be explained in the context of the across-neuron pattern theory. A matrix-pattern notion assumes that taste quality is coded by a spatially arranged matrix pattern of activated neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Shinomoto, Shigeru, Keisetsu Shima et Jun Tanji. « Differences in Spiking Patterns Among Cortical Neurons ». Neural Computation 15, no 12 (1 décembre 2003) : 2823–42. http://dx.doi.org/10.1162/089976603322518759.
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Spike sequences recorded from four cortical areas of an awake behaving monkey were examined to explore characteristics that vary among neurons. We found that a measure of the local variation of interspike intervals, LV, is nearly the same for every spike sequence for any given neuron, while it varies significantly among neurons. The distributions of LV values for neuron ensembles in three of the four areas were found to be distinctly bimodal. Two groups of neurons classified according to the spiking irregularity exhibit different responses to the same stimulus. This suggests that neurons in each area can be classified into different groups possessing unique spiking statistics and corresponding functional properties.
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Unda, Brianna K., Vickie Kwan et Karun K. Singh. « Neuregulin-1 Regulates Cortical Inhibitory Neuron Dendrite and Synapse Growth through DISC1 ». Neural Plasticity 2016 (2016) : 1–15. http://dx.doi.org/10.1155/2016/7694385.
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Cortical inhibitory neurons play crucial roles in regulating excitatory synaptic networks and cognitive function and aberrant development of these cells have been linked to neurodevelopmental disorders. The secreted neurotrophic factor Neuregulin-1 (NRG1) and its receptor ErbB4 are established regulators of inhibitory neuron connectivity, but the developmental signalling mechanisms regulating this process remain poorly understood. Here, we provide evidence that NRG1-ErbB4 signalling functions through the multifunctional scaffold protein, Disrupted in Schizophrenia 1 (DISC1), to regulate the development of cortical inhibitory interneuron dendrite and synaptic growth. We found that NRG1 increases inhibitory neuron dendrite complexity and glutamatergic synapse formation onto inhibitory neurons and that this effect is blocked by expression of a dominant negative DISC1 mutant, or DISC1 knockdown. We also discovered that NRG1 treatment increases DISC1 expression and its localization to glutamatergic synapses being made onto cortical inhibitory neurons. Mechanistically, we determined that DISC1 binds ErbB4 within cortical inhibitory neurons. Collectively, these data suggest that a NRG1-ErbB4-DISC1 signalling pathway regulates the development of cortical inhibitory neuron dendrite and synaptic growth. Given that NRG1, ErbB4, and DISC1 are schizophrenia-linked genes, these findings shed light on how independent risk factors may signal in a common developmental pathway that contributes to neural connectivity defects and disease pathogenesis.
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Doll, C. J., P. W. Hochachka et P. B. Reiner. « Effects of anoxia and metabolic arrest on turtle and rat cortical neurons ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 260, no 4 (1 avril 1991) : R747—R755. http://dx.doi.org/10.1152/ajpregu.1991.260.4.r747.
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The responses of turtle and rat cortical pyramidal neurons to various pharmacological treatments were measured using intracellular recordings. Turtle neurons survived both anoxia and pharmacological anoxia for 180 min with no noticeable effect. Rat pyramidal neurons responded with a loss in membrane resistance, followed by a transient hyperpolarization, and a subsequent depolarization to a zero membrane potential (41.3 +/- 6.5 min, anoxia; 25.8 +/- 12.6 min, pharmacological anoxia). Metabolic arrest caused a rapid loss in membrane resistance, transient hyperpolarization, and a rapid depolarization in both turtle (4.6 +/- 1.1 min) and rat (3.1 +/- 0.5 min) neurons. Iodoacetate alone had a similar effect on the rat as metabolic arrest (6.5 +/- 0.8 min), but the turtle exhibited more prolonged survival (53.5 +/- 4.6 min). Ouabain caused a rapid depolarization in the rat cortical neuron (8.6 +/- 1.1 min), but no initial loss in membrane resistance or a hyperpolarization. These results demonstrate that the turtle neuron, which survives anoxia, is no better at surviving total metabolic inhibition than the rat neuron. In addition, anoxia takes 13 times longer to depolarize a rat cortical neuron than metabolic arrest, and neither of these treatments is totally mimicked by ouabain alone.
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Collins, Christine E., Emily C. Turner, Eva Kille Sawyer, Jamie L. Reed, Nicole A. Young, David K. Flaherty et Jon H. Kaas. « Cortical cell and neuron density estimates in one chimpanzee hemisphere ». Proceedings of the National Academy of Sciences 113, no 3 (4 janvier 2016) : 740–45. http://dx.doi.org/10.1073/pnas.1524208113.
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The density of cells and neurons in the neocortex of many mammals varies across cortical areas and regions. This variability is, perhaps, most pronounced in primates. Nonuniformity in the composition of cortex suggests regions of the cortex have different specializations. Specifically, regions with densely packed neurons contain smaller neurons that are activated by relatively few inputs, thereby preserving information, whereas regions that are less densely packed have larger neurons that have more integrative functions. Here we present the numbers of cells and neurons for 742 discrete locations across the neocortex in a chimpanzee. Using isotropic fractionation and flow fractionation methods for cell and neuron counts, we estimate that neocortex of one hemisphere contains 9.5 billion cells and 3.7 billion neurons. Primary visual cortex occupies 35 cm2 of surface, 10% of the total, and contains 737 million densely packed neurons, 20% of the total neurons contained within the hemisphere. Other areas of high neuron packing include secondary visual areas, somatosensory cortex, and prefrontal granular cortex. Areas of low levels of neuron packing density include motor and premotor cortex. These values reflect those obtained from more limited samples of cortex in humans and other primates.
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Murray, Peter D., et Asaf Keller. « Somatosensory response properties of excitatory and inhibitory neurons in rat motor cortex ». Journal of Neurophysiology 106, no 3 (septembre 2011) : 1355–62. http://dx.doi.org/10.1152/jn.01089.2010.
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In sensory cortical networks, peripheral inputs differentially activate excitatory and inhibitory neurons. Inhibitory neurons typically have larger responses and broader receptive field tuning compared with excitatory neurons. These differences are thought to underlie the powerful feedforward inhibition that occurs in response to sensory input. In the motor cortex, as in the somatosensory cortex, cutaneous and proprioceptive somatosensory inputs, generated before and during movement, strongly and dynamically modulate the activity of motor neurons involved in a movement and ultimately shape cortical command. Human studies suggest that somatosensory inputs modulate motor cortical activity in a center excitation, surround inhibition manner such that input from the activated muscle excites motor cortical neurons that project to it, whereas somatosensory input from nearby, nonactivated muscles inhibit these neurons. A key prediction of this hypothesis is that inhibitory and excitatory motor cortical neurons respond differently to somatosensory inputs. We tested this prediction with the use of multisite extracellular recordings in anesthetized rats. We found that fast-spiking (presumably inhibitory) neurons respond to tactile and proprioceptive inputs at shorter latencies and larger response magnitudes compared with regular-spiking (presumably excitatory) neurons. In contrast, we found no differences in the receptive field size of these neuronal populations. Strikingly, all fast-spiking neuron pairs analyzed with cross-correlation analysis displayed common excitation, which was significantly more prevalent than common excitation for regular-spiking neuron pairs. These findings suggest that somatosensory inputs preferentially evoke feedforward inhibition in the motor cortex. We suggest that this provides a mechanism for dynamic selection of motor cortical modules during voluntary movements.
Thèses sur le sujet "Neuroni corticali"
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CURCIO, LIVIA. « Effetti degli amminoacidi a catena ramificata (BCAA) sull’eccitabilità di neuroni corticali in coltura primaria e confronto con il modello murino di sclerosi laterale amiotrofica, G93A ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1181.
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Recenti studi epidemiologici hanno accertato che, rispetto all’intera popolazione italiana, la categoria dei calciatori presenta una maggiore incidenza di casi di Sclerosi Laterale Amiotrofica (SLA). Una delle principali ipotesi relativa a questo dato è l’eccessivo utilizzo di integratori dietetici e farmaci che servono ad aumentare la performance sportiva ed a diminuire la sensazione di fatica. In particolare, è stato riscontrato che Valina, Leucina e Isoleucina (Branched Chain AminoAcids: BCAA) sono tra i supplementi maggiormente utilizzati tra gli atleti.
Per studiare i possibili effetti dei BCAA sulle proprietà elettriche neuronali sono stati effettuati esperimenti elettrofisiologici sui neuroni corticali primari provenienti da topi di controllo trattati con 200 µM di BCAA, ed i risultati ottenuti sono stati confrontati con quanto osservato nei neuroni di controllo non trattati.
Questi esperimenti hanno dimostrato che il trattamento induce un significativo aumento nell’eccitabilità neuronale in maniera dose e tempo–dipendente, rispetto ai neuroni di controllo non trattati. Inoltre, altri amminoacidi dotati di una catena laterale non ramificata, come per esempio l’Alanina e la Fenilalanina, non causano alcuna alterazione come quella riscontrata in seguito all’esposizione ai BCAA.
Studi condotti in modalità voltage-clamp hanno inoltre dimostrato che i neuroni trattati con i BCAA possiedono correnti voltaggio-dipendenti del Sodio persistente e del Calcio maggiori di quelle dei neuroni di controllo. Ciò indica che le modifiche delle proprietà biofisiche dei potenziali d’azione sono probabilmente dovute all’aumento nella densità in membrana dei canali specifici per queste specie ioniche.
La riscontrata ipereccitabilità e le alterazioni di funzionalità dei canali ionici di Sodio persistente e di Calcio indotte dai BCAA in cellule di controllo sono paragonabili a quelle riscontrate nei neuroni ottenuti da un modello murino di SLA, il topo G93A, evidenziando un’importante correlazione tra le due condizioni sperimentali.
Inoltre, è stato dimostrato che la Rapamicina, farmaco in grado di bloccare il complesso mTOR, favorisce il ripristino di una frequenza di scarica confrontabile con i valori di controllo, sia in cellule trattate con i BCAA che in neuroni G93A. Ciò potrebbe indicare che il complesso mTOR è coinvolto nelle alterazioni indotte dai BCAA e nella patogenesi della SLA.
La comprensione di come i BCAA influiscano sulle proprietà fisiologiche e funzionali dei neuroni corticali può permettere di stabilire un loro possibile coinvolgimento nell’eziopatogenesi della SLA contribuendo alla comprensione del probabile meccanismo d’azione interessato, al fine di individuare nuovi trattamenti terapeutici.Some epidemiological studies have recently ascertained that, Italian soccer players present a higher risk factor for Amyotrophic Lateral Sclerosis (ALS), compared to general population. One of the main hypotheses is related to the abuse of dietary supplements and drugs to enhance sporting performance and to reduce the feeling of fatigue. In particular, it has been reported that Valine, Leucine and Isoleucine (Branched-chain Amino Acids: BCAAs) are widely used among athletes. To study the possible effect of BCAAs on neuronal electrical properties, electrophysiological experiments have been performed on primary cortical neurons treated with 200 µM of BCAA and cultured from control embryos. All data have been compared to control values. The experiments have demonstrated that the treatment induces a significant increase of neuronal excitability dose- and time-dependent respect to control. Moreover, the treatment with other aminoacids, such as Alanine and Phenilalanine, doesn’t cause any alteration. Voltage clamp experiments show that, after a long exposition to BCAA, neurons present an increase of the Sodium and Calcium voltage-dependent channel densities. So, those biophysical changes could explain the increase of action potential frequencies observed after BCAA exposure. Both hyperexcitability and the higher Sodium and Calcium densities, induced by BCAA in control cells, were comparable to those obtained in the G93A neurons underlining an important correlation between two experimental conditions. Moreover, a treatment with Rapamycin, an inhibitor of the complex mTOR, was able to revert both the BCAA-induced and the G93A hyperexcitability to control values. These findings strongly indicates that in both cases, the mTOR signalling could be activated. In this way, the understanding of the effect mediated by BCAA on the functionality of primary cortical neurons and the mechanism of action will allow us to learn better the ethiopathogenesis of ALS, thus opening up new strategies for the treatment of this pathology.
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Markov, Nikola. « Exploration of the inter-areal cortico-cortical network of the macaque monkey ». Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00863803.
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The cortex can be viewed as a network of functional areas. A cortical area, composed ofneurons forming local connections, interacts with other areas via long distance connections.Each neuron receives multiple inputs and has to integrate the incoming signals. This integrativecapacity is the basis of the computational power of the brain. Our work concentrates onunderstanding the principles that govern the structure of the cortical network i.e. the allocationof neural resources as well as the anatomical segregation between processing steams. Usingretrograde tracer injections we extract two quantitative parameters: (i) the proportion ofSupragranular Labelled Neurons (SLN) identifies the feedforward (FF) or feedback (FB)operation between the source and target area; (ii) the Fraction of Labelled Neurons (FLN)identifies the magnitude of a connection pathway.We have made repeat injections in V1, V2, V4 to investigate the consistency of corticalpathways. This showed that (i) connection weights are consistent between animals; (ii) the listof areas projecting to each injection site is highly reproducible. We find that there are fixedFLN values for each pair of interconnected areas. The FLN values of all the afferent pathwaysto a given target span over a factor of 6 levels of log and although there is some overdispersiontheir variability is not larger than one single level of log meaning that there is a specificconnectivity profile for each area. Futermore the FLN follow a lognormal distribution. Inlognormals the mode is lower than the median and the mean i.e. the majority of pathways haveFLN weaker than the average FLN, meaning that strong projections are rare. If instead thedistribution of FLN was to follow a power law, then high FLN values would have been evenrarer. We found, a regularity in that the strongest input is invariably from within the injectedarea, second strongest are the inputs from areas sharing common borders with the target area.Sub-cortical inputs have a weak FLN, even when they are associated with an importantfunctional role such as the LGN → V1 pathway. We found that projection distance is inverselyrelated to the FLN value and an exponential distance rule operates that constrains short distanceprojections to high FLN and long distance projections to low FLN.We injected a total of 26 cortical areas homogenously distributed across the cortex. Thisrevealed 1232 projection pathways. Roughly 30% of pathways that we reveal have notpreviously been reported in the literature. Our ability to find new connections is due to theimproved tracing and brain segmentation techniques. We scan the whole brain at up to 80μmintervals to detect projection neurons, and this, as discussed in the text, is a major advantage toexisting studies. The weak long distance connections were shown to contract the characteristicpath-length of the graph (number of hops needed to go between any two areas).Our analysis of the graph showed that contrary to current belief the cortical inter-areal networkis dense (i.e. 58% of the connection that could exist do exist). At such a density, models basedon binary features such as small world cannot capture the specificity of the graph. Hence thecortex does not correspond small-world network, with sparse clustered graph possessingempowered by few critical projecitons that ensure short characteristic path-lengths. Furtheranalysis of pathway efficiency showed that the short distance connections of high magnitudeprovide large bandwidth for local connectivity and form a backbone of clustered functionallyrelated areas. This backbone is embedded in a sea of weak connections providing direct linksbetween cortical areas. We refer to this architecture as a tribal-network. We speculate that thesmall scale and high density that characterize the cortico-cortical network is facilitating theemergence of synchrony between cortical areas.
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Ponce, Alvarez Adrián. « Probabilistic models for studying variability in single-neuron and neuronal ensemble activity ». Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX20706.
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Une des caractéristiques les plus singulières de l’activité corticale est son degré élevé de variabilité. Ma thèse dedoctorat s’est focalisée sur l’étude de (i) l’irrégularité des intervalles entre potentiels d’action (PAs)successivement émis par un neurone, et (ii) la variabilité dans l’évolution temporelle de l’activité d’un ensemblede neurones. Premièrement, j’ai étudié l’irrégularité des neurones enregistrés dans le cortex moteur de singesmacaques performant une tâche d’estimation du temps et de préparation à l’action. J’ai montré que l’irrégularitén’est pas un paramètre libre de l’activité neuronale, contrairement au taux de PAs, mais est déterminée par lescontraintes structurelles des réseaux neuronaux. Deuxièmement, j’ai utilisé le modèle de Markov caché (MMC)pour analyser l’activité d’ensembles de neurones enregistrés dans plusieurs aires corticales, sensorielles etmotrices, de singes exécutant une tâche de discrimination tactile. J’ai montré que les processus sensoriels etdécisionnels sont distribués dans plusieurs aires corticales. Les résultats suggèrent que l’action et la décision surlaquelle elle est basée sont reliées par une cascade d’évènements non stationnaires et stochastiques. Finalement,j’ai utilisé le MMC pour caractériser l’activité spontanée d’un ensemble de neurones du cortex préfrontal d’unrat. Les résultats montrèrent que l’alternance entre les états UP et DOWN est un processus stochastique etdynamique. La variabilité apparaît donc aussi bien pendant l’activité spontanée que pendant le comportementactif et semble être contrainte par des facteurs structurels qui, à leur tour, contraignent le mode d’opération desréseaux neuronauxA hallmark of cortical activity is its high degree of variability. The present work focused on (i) the variability ofintervals between spikes that single neurons emit, called spike time irregularity (STI), and (ii) the variability inthe temporal evolution of the collective neuronal activity. First, I studied the STI of macaque motor corticalneurons during time estimation and movement preparation. I found that although the firing rate of the neuronstransmitted information about these processes, the STI of a neuron is not flexible and is determined by thebalance of excitatory and inhibitory inputs. These results were obtained by means of an irregularity measure thatI compared to other existing measures. Second, I analyzed the neuronal ensemble activity of severalsomatosensory and motor cortical areas of macaques during tactile discrimination. I showed that ensembleactivity can be effectively described by the Hidden Markov Model (HMM). Both sensory and decision-makingprocesses were distributed across many areas. Moreover, I showed that decision-related changes in neuronalactivity rely on a noise-driven mechanism and that the maintenance of the decision relies on transient dynamics,subtending the conversion of a decision into an action. Third, I characterized the statistics of spontaneous UP andDOWN states in the prefrontal cortex of a rat, using the HMM. I showed that state alternation is stochastic andthe activity during UP states is dynamic. Hence, variability is prominent both during active behavior andspontaneous activity and is determined by structural factors, thus rending it inherent to cortical organization andshaping the function of neural networks
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Grehl, Stephanie. « Stimulation-specific effects of low intensity repetitive magnetic stimulation on cortical neurons and neural circuit repair in vitro (studying the impact of pulsed magnetic fields on neural tissue) ». Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066706/document.
Texte intégralRésumé :
Les champs électromagnétiques sont couramment utilisés pour stimuler de manière non-invasive le cerveau humain soit à des fins thérapeutiques ou dans un contexte de recherche. Les effets de la stimulation magnétique varient en fonction de la fréquence et de l'intensité du champ magnétique. Les mécanismes mis en jeu restent inconnus, d'autant plus lors de stimulations à faible intensité. Dans cette thèse, nous avons évalué les effets de stimulations magnétiques répétées à différentes fréquences appliqués à faible intensité (10-13 mT ; Low Intensity Repetitive Magnetic Stimulation : LI-rMS) in vitro, sur des cultures corticales primaires et sur des modèles de réparation neuronale. De plus, nous décrivons une méthodologie pour la construction d'un dispositif instrumental fait sur mesure pour stimuler des cultures cellulaires.Les résultats montrent des effets dépendant de la fréquence sur la libération du calcium des stocks intracellulaires, sur la mort cellulaire, sur la croissance des neurites, sur la réparation neuronale, sur l'activation des neurones et sur l'expression de gènes impliqués. En conclusion, nous avons montré pour la première fois un nouveau mécanisme d'activation cellulaire par les champs magnétiques à faible intensité. Cette activation se fait en l'absence d'induction de potentiels d'action. Les résultats soulignent l'importance biologique de la LI-rMS par elle-même mais aussi en association avec les effets de la rTMS à haute intensité. Une meilleure compréhension des effets fondamentaux de la LI-rMS sur les tissus biologiques est nécessaire afin de mettre au point des applications thérapeutiques efficaces pour le traitement des conditions neurologiquesElectromagnetic fields are widely used to non-invasively stimulate the human brain in clinical treatment and research. This thesis investigates the effects of different low intensity (mT) repetitive magnetic stimulation (LI-rMS) parameters on single neurons and neural networks and describes key aspects of custom tailored LI-rMS delivery in vitro. Our results show stimulation specific effects of LI-rMS on cell survival, neuronal morphology, neural circuit repair and gene expression. We show novel mechanisms underlying cellular responses to stimulation below neuronal firing threshold, extending our understanding of the fundamental effects of LI-rMS on biological tissue which is essential to better tailor therapeutic applications
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BACIGALUPPI, SUSANNA. « Ruolo e potenziale delle cellule progenitrici endoteliali nel vasospamo cerebrale ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/27113.
Texte intégralRésumé :
Title: Role and potential of endothelial progenitor cells in cerebral vasospasm Abstract: Background and aim:
Despite many treatment approaches, cerebral vasospasm and delayed ischemic neuronal damage (DIND) still represent a serious threat to patients with subarachnoid haemorrhage (SAH). Endothelial progenitor cells (EPC) have been involved as prognostic indicators in several vascular diseases and mesenchymal stem cells already have shown some benefits in ischemic injury.
Aim of this study was to investigate the therapeutic potential of endothelial progenitor cells (EPC) and mesenchymal stem cells (MSC) in attenuating or preventing vasospasm and DIND in patients with SAH.
Methods:
Given the emergent role of DIND as a result of multifactorial hypoperfusion stress in the outcome of SAH patients, the efficacy of EPC and MSC in reducing neuronal damage has been evaluated in an in vitro model of ischemia, namely the oxygen glucose deprivation (OGD), on primary rat cortical neuronal cultures.
Further, we tested in a clinical observational study SAH patients with and without vasospasm for different recruitment patterns of circulating EPC. To this purpose arterial blood samples were collected at various timepoints from admission to discharge of the patients. On these samples real-time quantitative PCR (RT-qPCR) was performed to detect gene expression relative to EPCs, since cytofluorimetric analysis appeared not sensitive enough to detect this rare cell population.
Results:
Though present results need further confirmation, in vitro it was observed that both MSC and EPC treatment through conditioned medium or co-culture in transwell- although with some differences - mediate a survival advantage for OGD stressed neurons. Furthermore stem cell mediated treatment showed efficacy even when applied 24 hours after OGD stress induction.
RT-qPCR results from a small sample of SAH patients might indicate an early mobilization of EPC related gene expression in subjects that do not develop vasospasm with a peak around day 4, whereas the expression of these genes remain invariably low in patients that develop vasospasm as in controls not affected by SAH.
Conclusions:
MSCs and EPCs seem to have an important potential role in preventing DIND in vitro as well as EPC recruitment might associate with lack of vasospasm in SAH patients.
Further studies are needed to confirm these results and to prove a causal relationship between EPCs and vasospasm protection.
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Verzeaux, Laurie. « Etude de l'interaction du TIMP-1 avec ses récepteurs ». Thesis, Reims, 2015. http://www.theses.fr/2015REIMS040/document.
Texte intégralRésumé :
Le TIMP-1, inhibiteur naturel des métalloprotéinases matricielles, exerce des effets pléïotropes indépendants de l'inhibition des MMPs et participe au développement de certains cancers et maladies neurodégénératives. Ces effets cytokiniques du TIMP-1 impliquent sa liaison à des récepteurs membranaires dont certains sont caractérisés, la glycoprotéine CD63/intégrine beta 1 et le complexe pro MMP-9/CD44. Cependant les acides aminés ou les domaines du TIMP-1 se liant à ces récepteurs ne sont pas identifiés. Les travaux réalisés au cours de cette thèse mettent en évidence un nouveau récepteur du TIMP-1, la protéine LRP-1. Dans les neurones corticaux murins, le TIMP-1 se fixe aux domaines DII et DIV de LRP-1, est endocyté et induit une réduction de la taille des neurites ainsi qu'une augmentation du volume des cônes de croissance. Afin de caractériser cette interaction, nous avons utilisé une approche originale de modélisation moléculaire associant les analyses de modes normaux et la dynamique moléculaire. Ces analyses in silico ont permis d'identifier un mouvement de pince entre les domaines N et C-terminaux du TIMP-1. Nous avons muté trois résidus (F12, K47 et W105) localisés dans une région essentielle d'un point vue énergétique à l'exécution de ce mouvement. Ces trois mutants n'ont pas d'effet sur la longueur du réseau neuritique et ne sont pas endocytés par LRP-1. En revanche, ils interagissent avec les 2 autres récepteurs (CD63 et proMMP-9) et reproduisent les effets du TIMP-1 sauvage. De plus, nous avons identifié une séquence de 6 acides aminés localisée dans le domaine extracellulaire I de CD63 et essentielle à la liaison avec le TIMP-1. L'ensemble de ces travaux a permis l'identification de régions impliquées dans l'interaction du TIMP-1 avec ses différents récepteurs et pourrait permettre le développement de nouveaux outils pharmacologiques ciblant les activités cytokiniques du TIMP-1TIMP-1, a natural inhibitor of matrix metalloproteinases, exerts pleiotropic effects independent of MMP inhibition and thus participates to the development of some cancers and neurodegenerative disorders. These cytokine-like activities require TIMP-1 binding to membrane receptors. Up to date two receptors, CD63/integrin beta 1 and proMMP-9/CD44, have been characterized. Nevertheless, TIMP-1 residues or regions binding these receptors remain unknown. In this work, we have identified the protein LRP-1 as a new receptor for TIMP 1. In mouse cortical neurons, TIMP-1 preferentially binds DII and DIV domains of LRP-1, is internalized via a LRP-1-dependent endocytosis, reduces neurite length and increases growth cone volume. To go deeper into TIMP-1/LRP-1 interaction, we used an original molecular modeling approach which combined normal mode analysis and molecular dynamic. These in silico studies allow us to point out a clamp movement between the N- and C-terminal domains of TIMP-1. Three residues localized in a region that seems essential for the movement have been mutated (F12, K47 and W105) and single mutants have been produced. These mutants do not reduce neurite outgrowth and are not internalized by LRP-1. In contrast, they interact with the two others receptors proMMP-9 and CD63 and induce associated biological effects. Furthermore, we have identified a sequence of six residues localized in the CD63 extracellular domain I and essential for TIMP 1 binding. The set of our data highlighted new regions of TIMP-1 interacting with its receptors and could lead to design novel therapeutic agents targeting the TIMP-1 cytokine like activities
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Dobbins, Allan C. (Allan Charles). « Difference models of visual cortical neurons ». Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39539.
Texte intégralRésumé :
Difference operations are ubiquitous in the visual cortex. The central hypothesis in this thesis is that a nonlinear difference model can account for the functional properties of three different classes of visual cortical neurons. Abstractly each of the different neurons can be understood in terms of the same difference model although the computations they perform can be entirely different.Endstopped neurons respond to short or highly curved oriented patterns. Their behaviour results from the difference in activation of their classical receptive field and inhibitory endzones. Two models of endstopped neurons are evaluated mathematically and by computer simulation. It is concluded that a model with displaced complex cell-like endzones is both more computationally robust and more consistent with the physiological evidence.
Other visual cortical neurons have inhibitory zones which are displaced normally rather than tangentially with respect to the neuron's receptive field orientation. These sidestopped cells are selective for narrow patterns. In other visual cortical neurons the side inhibition is derived from a different eye than the classical receptive field. Because of the geometry of projection these are referred to as binocular Near and Far cells. A difference model of sidestopped and Near and Far neurons is developed which captures their principal features.
Neurons in visual cortical area MT of primates have been shown to exhibit a velocity-specific antagonism between the receptive field and a surrounding region. It is argued that center-surround antagonism is an attempt to resolve competing constraints. Signal reliability increases with spatial averaging, but the variation of the flow field invariably increases with area. A unifying perspective is that difference models provide a means of estimating the range over which a visual quantity is constant or linear. Varieties of these models exist with a more refined property--selectivity for sign of contour curvature or, under certain circumstances, the sign of convexity of the surface generating a binocular disparity or motion field.
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Qin, Yan. « Studies of Zinc Transport and Its Contribution to Zinc Homeostasis in Cultured Cortical Neurons ». View abstract, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3339515.
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Lackmy, Alexandra. « Stimulation magnétique transcrânienne et inhibition intra-corticale : variabilité liée au recrutement des motoneurones spinaux et des neurones corticaux ». Paris 6, 2010. http://www.theses.fr/2010PA066060.
Texte intégralRésumé :
L’activation "transynaptique" des neurones pyramidaux du cortex moteur primaire par stimulation magnétique transcrânienne (TMS) induit des volées corticospinales (CSP) transmises aux motoneurones spinaux. Leur activation entraîne une contraction traduite par un potentiel (PEM) dans l’activité électromyographique du muscle cible. L’amplitude du PEM en mV sert à évaluer l’état d’excitabilité des neurones de la voie CSP. Si une TMS conditionnante précède de 2 à 5 ms une TMS test, le PEM évoqué par le double choc de TMS est plus petit que le PEM induit par la TMS test seule. Cette inhibition, la SICI, vient de l’activation d’interneurones inhibiteurs qui modifient la réponse des neurones pyramidaux à la TMS test. La variabilité des résultats remet en cause la fiabilité de cette méthode. Plusieurs paramètres ont été testés, mais jamais les propriétés des neurones corticaux et spinaux n’ont été suspectées. L’objectif du projet doctoral était de vérifier si les propriétés de ces neurones influencent l’évaluation de la SICI chez l’Homme. Le PEM test a été exprimé en % de la réponse motrice maximale (Mmax), plutôt qu’en mV, pour évaluer la fraction de MNs recrutés par la TMS test. Des unités motrices isolées ont été testées pour explorer les réponses des neurones corticaux à la TMS. Les résultats ont révélé que i) la sommation des volées CSP au niveau des MNs n’est pas linéaire ce qui influence l’évaluation de la SICI, ii) l’intégration des entrées synaptiques inhibitrices au niveau des réseaux corticaux afférents aux cellules pyramidales n’est pas linéaire. Ce travail a permis de proposer une nouvelle méthode d’évaluation des mécanismes corticaux révélés avec la TMS.
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Zhou, Yi-Xiong. « Responses to envelope patterns in visual cortical neurons ». Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41806.
Texte intégralRésumé :
Mammalian striate and circumstriate cortical neurons have long been understood as coding spatially localized retinal luminance variations, providing a basis for computing motion, stereopsis, and contours from the retinal image. However, such perceptual attributes do not always correspond to the retinal luminance variations in natural vision. Recordings from area 17 and 18 neurons revealed a specialized nonlinear processing stream that responded to stimulus attributes having no corresponding luminance variations. This nonlinear stream acts in parallel to the conventional luminance processing of single cortical neurons. The two streams were consistent in their preference for orientation and direction of motion, but distinct in processing spatial variations of the stimulus attributes. The ensemble of these neurons provides a combination of stimulus attributes with and without corresponding luminance variations.
Livres sur le sujet "Neuroni corticali"
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N, Cooper Leon, dir. Theory of cortical plasticity. New Jersey : World Scientific, 2004.
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Neuronal Topography in a Cortical Circuit for Innate Odor Valence. [New York, N.Y.?] : [publisher not identified], 2020.
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Sam, Fazeli, et Collingridge G. L, dir. Cortical plasticity : LTP and LTD. Oxford : Bios Scientific, 1996.
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Ghai, Himesh S. Anoxia reduces whole cell permeability in cortical neurons of the anoxia tolerant turtle, Chrysemys picta belli. Ottawa : National Library of Canada, 1999.
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Coordinated activity in the brain : Measurements and relevance to brain function and behavior. Dordrecht : Springer, 2009.
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P, Rauschecker Josef, et Marler Peter, dir. Imprinting and cortical plasticity : Comparative aspects of sensitive periods. New York : Wiley, 1987.
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Sattler, Rita. Effects of moderate and profound hypothermia on excitatory amino-acid-induced neuronal injury in cortical cell cultures. Ottawa : National Library of Canada, 1996.
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Żochowski, Michał. Synchrony in biological and physical systems : An experimental and theoretical study. Warszawa : Polska Akademia Nauk, Instytut Biocybernetyki i Inżynierii Biomedycznej, 2000.
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Gutnick, Michael J., et Istvan Mody, dir. The Cortical Neuron. Oxford University Press, 1995. http://dx.doi.org/10.1093/acprof:oso/9780195083309.001.0001.
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J, Gutnick M., et Mody Istvan 1957-, dir. The cortical neuron. New York : Oxford University Press, 1995.
Trouver le texte intégralChapitres de livres sur le sujet "Neuroni corticali"
1
Stetter, Martin. « Neurons and Neuronal Signal Propagation ». Dans Exploration of Cortical Function, 5–22. Dordrecht : Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0430-5_2.
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White, Edward L. « Functional Properties of Cortical Neurons ». Dans Cortical Circuits, 109–31. Boston, MA : Birkhäuser Boston, 1989. http://dx.doi.org/10.1007/978-1-4684-8721-3_4.
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Kawaguchi, Yasuo. « Hierarchical Organization of Neocortical Neuron Types ». Dans Cortical Development, 181–202. Tokyo : Springer Japan, 2013. http://dx.doi.org/10.1007/978-4-431-54496-8_8.
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Storm-Mathisen, Jon, et Ole Petter Ottersen. « Anatomy of Putative Glutamatergic Neurons ». Dans Neurotransmitters and Cortical Function, 39–70. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0925-3_4.
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Renaud, Leo P. « Electrophysiology of a Peptidergic Neuron ». Dans Neurotransmitters and Cortical Function, 495–515. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0925-3_32.
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Tian, Guohong, et Xinghuai Sun. « Cortical Blindness ». Dans Neuro-Ophthalmology, 367–85. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-4668-4_14.
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Chrétien, M., R. A. Sikstrom, C. Lazure et N. G. Seidah. « Neuronal and Endocrine Peptides ». Dans Neurotransmitters and Cortical Function, 517–26. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0925-3_33.
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Braitenberg, Valentino, et Almut Schüz. « Classification of Cortical Neurons ». Dans Anatomy of the Cortex, 75–86. Berlin, Heidelberg : Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-662-02728-8_15.
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Braitenberg, Valentino, et Almut Schüz. « Classification of Cortical Neurons ». Dans Cortex : Statistics and Geometry of Neuronal Connectivity, 67–77. Berlin, Heidelberg : Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03733-1_15.
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Arecchi, Fortunato Tito. « Chaotic Neuron Dynamics, Synchronization, and Feature Binding ». Dans Computational Neuroscience : Cortical Dynamics, 90–108. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-27862-7_5.
Texte intégralActes de conférences sur le sujet "Neuroni corticali"
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Gao, Jianbo, Yi Zheng et Jing Hu. « Long-Range Temporal Correlations, Multifractality, and the Causal Relation Between Neural Inputs and Movements ». Dans ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-6081.
Texte intégralRésumé :
Understanding the causal relation between neural inputs and movements is very important for the success of brain machine interfaces (BMIs). In this study, we perform systematic statistical and information theoretical analysis of neuronal firings of 104 neurons, and employ three different types of fractal and multifractal techniques (including Fano factor analysis, multifractal detrended fluctuation analysis (MF-DFA), and wavelet multifractal analysis) to examine whether neuronal firings related to movements may have long-range temporal correlations. We find that MF-DFA and wavelet multifractal analysis (but not Fano factor analysis) clearly indicate that when neuronal firings are not well correlated with movement trajectory, they do not have or only have weak temporal correlations. When neuronal firings are well correlated with movements, they are characterized by very strong temporal correlations, up to a time scale comparable to the average time between two successive reaching tasks. This suggests that neurons well correlated with hand trajectory experienced a “re-setting” effect at the start of each reaching task. We further discuss the significance of the coalition of those important neurons in executing cortical control of prostheses.
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Silva, Matheus Henrique de Freitas, Pedro Ivo Machado Campos Araújo Costa, André Iglesias Brandão, Danilo Jorge Silva, Leopoldo Antonio Pires et Luiz Paulo Bastos Vasconcelos. « Gray matter heterotopy as a cause of seizure : purpose of a case diagnosed in adults ». Dans XIII Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2021. http://dx.doi.org/10.5327/1516-3180.325.
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Context: Epilepsy affects more than 50 million people worldwide, which is an important cause of morbidity and functional limitations. Cortical development malformations represent about 8% of epilepsy cases, and are associated with cognitive deficits, that are frequently diagnosed in childhood. Case report: L.G.M, female, 35 years old, was attended in an emergency department with psychotic symptoms, aggressiveness and lowering of the sensorium. Computed Tomography (CT) scan of the brain evidenced hypodensity and loss of cortico-medullary differentation in the left temporo-parietal region. The neuroimaging findings motivated the referral to our service for investigation. Upon admission, has been shown a history of frequent focal motor and non-motor seizures associated with cognitive deficit since the age of 12. During hospitalization, a Magnetic Resonance Imaging (MRI) of the brain was performed, which showed subependymal heterotopy of gray matter (Figures 1 and 2). Since then, the monotherapy treatment with carbamazepine aiming at seizure control was chosen. Discussion and conclusion: Cortical development malformations can be classified into three groups of abnormalities, such as: 1) neuronal and glial proliferation and apoptosis; 2) neuronal migration; 3) cortical organization. A heterotopy of the gray matter is related to the migration disorder of the germinal matrix neurons on the wall of ventricle lateral to the cortex. It is the most frequent anomaly of cortical development. The perception of cognitive deficit associated with epileptic seizures should always awaken to the need for early investigation by image examination, in particular brain MRI, in order to diagnose possible malformations of cortical development.
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Hallett, Peter E. « Eye size and neuron counts in mouse and rat ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.wl3.
Texte intégralRésumé :
Photoreceptors and neurons at various levels to cortex have been counted in mouse and rat. The ratios of neuron numbers (rat/mouse) are similar to the ratio of retinal areas or the squared ratio of eye sizes; so to a first approximation the two species have linearly scaled eyes, equal photoreceptor spacings (in microns), and visual pathways scaled numerically by the number of photoreceptors. The following points can be made: Photoreceptors outnumber neurons at all subsequent levels. Cone sampling exceeds the behavioral acuity limit, the latter being largely determined at or before the ganglion cell level. There are few neurons in the LGNd, and so the corresponding eye parameter p is very large, as is appropriate for nocturnal animals. The general organization is economical, if not sparse, so undersampling occurs even for central vision when the pupils are small. However, aliasing should be slight if the retinal and geniculate sampling lattices are irregular with only a local spatial order. Cortical encoding appears less explicit than in the primate. This seems compatible with either the photon limitations of nocturnal vision or the advantages of a fast though limited range of behavior.
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Lennie, Peter. « Cortical mechanisms of color vision ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.thp2.
Texte intégralRésumé :
In macaque monkey three distinct pathways relay information from the lateral geniculate nucleus (LGN) to the striate cortex. Two parvocellular pathways contain neurons with chromatically opponent receptive fields: one receives opposed inputs from R cones and G cones; the other receives inputs from B cones opposed by some combined signal from R and G cones. A distinctive feature of the R–G neurons (much the largest group in the LGN) is that they respond well to chromatic patterns of low spatial frequency and achromatic patterns of high spatial frequency. Magnocellular neurons receive inputs from all three classes of cone.
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Sengor, N. Serap, Yusuf Kuyumcu et Koray Ciflci. « Modeling cortical states by spiking neurons ». Dans 2014 22nd Signal Processing and Communications Applications Conference (SIU). IEEE, 2014. http://dx.doi.org/10.1109/siu.2014.6830461.
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Pereira, João Guilherme, Matheus de Freitas Oliveira Baffa, Fabrício Henrique Simozo, Luiz Otavio Murta Junior et Joaquim Cezar Felipe. « On The Use of Machine Learning Algorithms to Classify Focal Cortical Dysplasia on MRI ». Dans Simpósio Brasileiro de Computação Aplicada à Saúde. Sociedade Brasileira de Computação - SBC, 2021. http://dx.doi.org/10.5753/sbcas.2021.16063.
Texte intégralRésumé :
Refractory epilepsy is a condition characterized by epileptic seizure occurrence which cannot be controlled with antiepileptic drugs. This condition is associated with an excessive neuronal discharge produced by a group of neurons in a certain epileptogenic zone. Focal Cortical Dysplasia (FCD), usually found in these zones, was detected as one of the main causes of refractory epilepsy. In these cases, surgical intervention is necessary to minimize or eliminate the seizure occurrences. However, surgical treatment is only indicated in cases where there is complete certainty of the FCD. In order to assist neurosurgeons to detect precisely these regions, this paper aims to develop a classification method to detect FCD on MRI based on morphological and textural features from a voxel-level perspective. Multiple classifiers were tested throughout the extracted features, the best results achieved an accuracy of 91.76% using a Deep Neural Network classifier and 96.15% with J48 Decision Tree. The set of evaluating metrics showed that the results are promising.
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Watson, Andrew B. « Constraints on sensitivity of linear visual neurons ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.tuh4.
Texte intégralRésumé :
Many visual neurons linearly combine signals from the receptors or from other cells which themselves form linear combinations of receptor signals. In both cases, if the noise that limits cell performance is confined to the receptors, the peak sensitivity of the cell is entirely determined by the magnitude of the receptor noise and the normalized shape of the cells’ receptive field. This simple result may be used to estimate the receptor noise from the sensitivity of retinal or geniculate cells as well as to predict sensitivity of higher-order cells from that of lower-order cells. Consequences of this constraint are illustrated for actual primate geniculate and cortical cells and for model cortical cells.
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Zeringue, Henry C. « Microtechnologies for Neurobiology ». Dans ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13341.
Texte intégralRésumé :
Oscillatory activity in cortical networks is thought to provide the foundation for many high-level processes including working memory and attention. It has been shown that spatial information propagation delay and connectivity density can determine the innate properties of local network activity. The initial formation of neuronal networks in the central nervous system occurs due to the interaction of the genetic programming of the cells and the presentation of external molecular cues. The activity-driven refinement that occurs later, giving rise to the highly complex networks within the brain, are dependent on the initial anatomical formation and structural connectivity which occurs without external activity cues. We describe technologies used to (1) modulate the genetic programming of neurons and (2) precisely control temporal and spatial presentation of environmental cues in vitro. We are exploring the ability to define simple oscillatory networks using these experimental techniques.
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Sharma, Shivangi, et Jasdeep Kaur Dhanoa. « Analog Circuit Implementation of a Cortical Neuron ». Dans 2020 5th IEEE International Conference on Recent Advances and Innovations in Engineering (ICRAIE). IEEE, 2020. http://dx.doi.org/10.1109/icraie51050.2020.9358377.
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Wijekoon, Jayawan H. B., et Piotr Dudek. « Integrated circuit implementation of a cortical neuron ». Dans 2008 IEEE International Symposium on Circuits and Systems - ISCAS 2008. IEEE, 2008. http://dx.doi.org/10.1109/iscas.2008.4541785.
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