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Artigos de revistas sobre o assunto "Discrimination neuronale"
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Deng, Yingchun, Peter Williams, Feng Liu e Jianfeng Feng. "Neuronal discrimination capacity". Journal of Physics A: Mathematical and General 36, n.º 50 (1 de dezembro de 2003): 12379–98. http://dx.doi.org/10.1088/0305-4470/36/50/003.
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Smith, Jackson E. T., e Andrew J. Parker. "Correlated structure of neuronal firing in macaque visual cortex limits information for binocular depth discrimination". Journal of Neurophysiology 126, n.º 1 (1 de julho de 2021): 275–303. http://dx.doi.org/10.1152/jn.00667.2020.
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Correlated noise reduces the stimulus information in visual cortical neurons during experimental performance of binocular depth discriminations. The temporal scale of these correlations is important. Rapid (20–30 ms) correlations reduce information within and between areas V1 and V4, whereas slow (>100 ms) correlations between areas do not. Separate cortical areas appear to act together to maintain signal fidelity. Rapid correlations reduce the neuronal signal difference between stimuli and adversely affect perceptual discrimination.
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Spitzer, H., R. Desimone e J. Moran. "Increased attention enhances both behavioral and neuronal performance". Science 240, n.º 4850 (15 de abril de 1988): 338–40. http://dx.doi.org/10.1126/science.3353728.
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Single cells were recorded from cortical area V4 of two rhesus monkeys (Macaca mulatta) trained on a visual discrimination task with two levels of difficulty. Behavioral evidence indicated that the monkeys' discriminative abilities improved when the task was made more difficult. Correspondingly, neuronal responses to stimuli became larger and more selective in the difficult task. A control experiment demonstrated that changes in general arousal could not account for the effects of task difficulty on neuronal responses. It is concluded that increasing the amount of attention directed toward a stimulus can enhance the responsiveness and selectivity of the neurons that process it.
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MERIGAN, WILLIAM H. "Cortical area V4 is critical for certain texture discriminations, but this effect is not dependent on attention". Visual Neuroscience 17, n.º 6 (novembro de 2000): 949–58. http://dx.doi.org/10.1017/s095252380017614x.
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This study examined the question of which features of a complex grouping discrimination make it vulnerable to permanent elimination by V4 lesions. We first verified that the line element grouping discrimination, which we previously reported to be devastated by V4 lesions, was similarly affected in the monkeys of this study. The permanence of the deficit was established by mapping its visual field distribution and then testing this discrimination for an extended period at a locus on the border of the deficit. Also, a staircase procedure was used to provide the monkey with within session instruction in the grouping discrimination, but this did not improve V4 lesion performance. Grouping was then compared with several discriminations that shared some features with it, but which were found not to be permanently eliminated by V4 lesions. This comparison suggested that grouping (rather than segmentation or response to a single element) was one feature that made the discrimination vulnerable, a second was the similarity in shape of the texture elements to be grouped. Finally, we tested visual crowding, a property of peripheral vision that is thought to reflect neuronal interactions early in visual cortex, possibly in area V1, and found no effect of V4 lesions. A control experiment with human observers tested whether the elimination of grouping by V4 lesions might be due to an alteration of attention, but found no evidence to support this hypothesis. These results show that severe disruption of texture discriminations by V4 lesions depends on both the nature of the discrimination and the type of texture elements involved, but does not necessarily involve the disruption of attention.
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Boynton, Geoffrey M., Jonathan B. Demb, Gary H. Glover e David J. Heeger. "Neuronal basis of contrast discrimination". Vision Research 39, n.º 2 (janeiro de 1999): 257–69. http://dx.doi.org/10.1016/s0042-6989(98)00113-8.
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Arabzadeh, Ehsan, Colin W. G. Clifford, Justin A. Harris, David A. Mahns, Vaughan G. Macefield e Ingvars Birznieks. "Single tactile afferents outperform human subjects in a vibrotactile intensity discrimination task". Journal of Neurophysiology 112, n.º 10 (15 de novembro de 2014): 2382–87. http://dx.doi.org/10.1152/jn.00482.2014.
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We simultaneously compared the sensitivity of single primary afferent neurons supplying the glabrous skin of the hand and the psychophysical amplitude discrimination thresholds in human subjects for a set of vibrotactile stimuli delivered to the receptive field. All recorded afferents had a dynamic range narrower than the range of amplitudes across which the subjects could discriminate. However, when the vibration amplitude was chosen to be within the steepest part of the afferent's stimulus-response function the response of single afferents, defined as the spike count over the vibration duration (500 ms), was often more sensitive in discriminating vibration amplitude than the perceptual judgment of the participants. We quantified how the neuronal performance depended on the integration window: for short windows the neuronal performance was inferior to the performance of the subject. The neuronal performance progressively improved with increasing spike count duration and reached a level significantly above that of the subjects when the integration window was 250 ms or longer. The superiority in performance of individual neurons over observers could reflect a nonoptimal integration window or be due to the presence of noise between the sensory periphery and the cortical decision stage. Additionally, it could indicate that the range of perceptual sensitivity comes at the cost of discrimination through pooling across neurons with different response functions.
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Sanders, Teresa H., Mark A. Clements e Thomas Wichmann. "Parkinsonism-related features of neuronal discharge in primates". Journal of Neurophysiology 110, n.º 3 (1 de agosto de 2013): 720–31. http://dx.doi.org/10.1152/jn.00672.2012.
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Parkinson's disease is known to be associated with abnormal electrical spiking activities of basal ganglia neurons, including changes in firing rate, bursting activities and oscillatory firing patterns and changes in entropy. We explored the relative importance of these measures through optimal feature selection and discrimination analysis methods. We identified key characteristics of basal ganglia activity that predicted whether the neurons were recorded in the normal or parkinsonian state. Starting with 29 features extracted from the spike timing of neurons recorded in normal and parkinsonian monkeys in the internal or external segment of the globus pallidus or the subthalamic nucleus (STN), we used a method that incorporates a support vector machine algorithm to find feature combinations that optimally discriminate between the normal and parkinsonian states. Our results demonstrate that the discrimination power of combinations of specific features is higher than that of single features, or of all features combined, and that the most discriminative feature sets differ substantially between basal ganglia structures. Each nucleus or class of neurons in the basal ganglia may react differently to the parkinsonian condition, and the features used to describe this state should be adapted to the neuron type under study. The feature that was overall most predictive of the parkinsonian state in our data set was a high STN intraburst frequency. Interestingly, this feature was not correlated with parameters describing oscillatory firing properties in recordings made in the normal condition but was significantly correlated with spectral power in specific frequency bands in recordings from the parkinsonian state (specifically with power in the 8–13 Hz band).
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Spencer, K., e P. Carpenter. "Neurone Specific Enolase in Amniotic Fluid: A Potential Marker of Anencephaly". Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 25, n.º 1 (janeiro de 1988): 85–88. http://dx.doi.org/10.1177/000456328802500112.
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Normal values for neurone specific enolase in amniotic fluid have been found to follow a non gaussian distribution with a 1–99 centile range of 1·10–4·32 μg/L. Neurone specific enolase levels have been shown to be raised in the amniotic fluid of pregnancies complicated by anencephaly, although not those complicated by open spina bifida. Neurone specific enolase measured by radioimmunoassay is capable of totally discriminating between normal pregnancies and those complicated by anencephaly. The study demonstrates the possible value of investigating other neuronal proteins which may find value as adjuncts to amniotic fluid Alpha fetoprotein levels in the prenatal diagnosis of Neural Tube Defects.
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Heuer, Hilary W., e Kenneth H. Britten. "Optic Flow Signals in Extrastriate Area MST: Comparison of Perceptual and Neuronal Sensitivity". Journal of Neurophysiology 91, n.º 3 (março de 2004): 1314–26. http://dx.doi.org/10.1152/jn.00637.2003.
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The medial superior temporal area of extrastriate cortex (MST) contains signals selective for nonuniform patterns of motion often termed “optic flow.” The presence of such tuning, however, does not necessarily imply involvement in perception. To quantify the relationship between these selective neuronal signals and the perception of optic flow, we designed a discrimination task that allowed us to simultaneously record neuronal and behavioral sensitivities to near-threshold optic flow stimuli tailored to MST cells' preferences. In this two-alternative forced-choice task, we controlled the salience of globally opposite patterns (e.g., expansion and contraction) by varying the coherence of the motion. Using these stimuli, we could both relate the sensitivity of neuronal signals in MST to the animal's behavioral sensitivity and also measure trial-by-trial correlation between neuronal signals and behavioral choices. Neurons in MST showed a wide range of sensitivities to these complex motion stimuli. Many neurons had sensitivities equal or superior to the monkey's threshold. On the other hand, trial-by-trial correlation between neuronal discharge and choice (“choice probability”) was weak or nonexistent in our data. Together, these results lead us to conclude that MST contains sufficient information for threshold judgments of optic flow; however, the role of MST activity in optic flow discriminations may be less direct than in other visual motion tasks previously described by other laboratories.
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Li, Wu, Peter Thier e Christian Wehrhahn. "Contextual Influence on Orientation Discrimination of Humans and Responses of Neurons in V1 of Alert Monkeys". Journal of Neurophysiology 83, n.º 2 (1 de fevereiro de 2000): 941–54. http://dx.doi.org/10.1152/jn.2000.83.2.941.
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We studied the effects of various patterns as contextual stimuli on human orientation discrimination, and on responses of neurons in V1 of alert monkeys. When a target line is presented along with various contextual stimuli (masks), human orientation discrimination is impaired. For most V1 neurons, responses elicited by a line in the receptive field (RF) center are suppressed by these contextual patterns. Orientation discrimination thresholds of human observers are elevated slightly when the target line is surrounded by orthogonal lines. For randomly oriented lines, thresholds are elevated further and even more so for lines parallel to the target. Correspondingly, responses of most V1 neurons to a line are suppressed. Although contextual lines inhibit the amplitude of orientation tuning functions of most V1 neurons, they do not systematically alter the tuning width. Elevation of human orientation discrimination thresholds decreases with increasing curvature of masking lines, so does the inhibition of V1 neuronal responses. A mask made of straight lines yields the strongest interference with human orientation discrimination and produces the strongest suppression of neuronal responses. Elevation of human orientation discrimination thresholds is highest when a mask covers only the immediate vicinity of the target line. Increasing the masking area results in less interference. On the contrary, suppression of neuronal responses in V1 increases with increasing mask size. Our data imply that contextual interference observed in human orientation discrimination is in part directly related to contextual inhibition of neuronal activity in V1. However, the finding that interference with orientation discrimination is weaker for larger masks suggests a figure-ground segregation process that is not located in V1.
Teses / dissertações sobre o assunto "Discrimination neuronale"
1
Ménardy, Fabien. "Reconnaissance des signaux de communication chez le diamant mandarin : étude des réponses des neurones d’une aire auditive secondaire". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA11T049/document.
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A l’heure actuelle, il reste largement à étudier comment le codage sensoriel des signaux vocaux de communication contribue à leur détection et à leur reconnaissance. Peu d’études se sont, en effet, penchées sur le codage des vocalisations au niveau des régions auditives en fonction de l’individu qui les produit et du degré de familiarité avec cet individu. Dans ce cadre, les oiseaux chanteurs sont un bon modèle parce qu’ils utilisent des vocalisations pour interagir et reconnaître leurs congénères et qu’ils possèdent, de plus, un ensemble de régions auditives. Parmi ces régions, le nidopallium caudomedian (NCM), une aire auditive analogue du cortex auditif secondaire chez les mammifères, est actuellement considérée comme une région spécialisée dans le traitement des vocalisations (chants et cris) de l’espèce : les neurones du NCM répondent plus fortement aux vocalisations de l’espèce qu’à celles d’une autre espèce. À partir de là, parce que chez le diamant mandarin, le cri de distance permet aux individus, mâles ou femelles, de reconnaître leur partenaire sexuel, nous avons cherché à savoir si, chez les femelles comme chez les mâles, les neurones du NCM montraient une discrimination dans leurs réponses auditives entre le cri d’individus connus (parmi lesquels figurait le partenaire sexuel) et ceux d’individus inconnus et si ces réponses reflétaient le degré de familiarité de ces vocalisations. Les enregistrements de l’activité des neurones du NCM, chez des diamants mandarins vigiles (grâce à un système de télémétrie) ou anesthésiés, lors de la présentation de cris de distance, ont révélé, chez les femelles vivant en couple et ayant été familiarisées avec un autre couple de diamants mandarins, une plus forte augmentation de l’activité lors de la diffusion des cris d’individus connus, mâles ou femelles, qu’aux cris d’individus inconnus. Une telle augmentation n’a pas été, en outre, observée chez des femelles contrôles qui n’avaient jamais entendu ces mêmes cris auparavant. De plus, ils ont indiqué que le nombre de neurones montrant un fort degré de sélectivité ainsi que la quantité d’information portée par les trains de potentiels d’action étaient plus importants chez les femelles vivant en couple que chez les femelles contrôles. En revanche, chez les mâles, bien que la plupart des neurones montrait des réponses lors de la diffusion des cris, aucune différence n’a été mise en évidence entre les cris d’individus connus et ceux d’inconnus. Nous avons alors cherché à savoir comment, d’un point de vue acoustique, les cris de distance étaient représentés au sein du NCM. En se basant sur une étude comportementale ayant déterminé quelles étaient les caractéristiques acoustiques qui contribuaient à la reconnaissance de ces cris, nous avons cherché à savoir si les neurones du NCM étaient sensibles à ces mêmes caractéristiques acoustiques. Les résultats ont montré que, chez les femelles, la suppression de la fréquence fondamentale et la modification du timbre du cri du partenaire sexuel ou du propre cri de l’oiseau provoquaient une forte diminution des réponses au sein du NCM alors que, chez les mâles, les réponses variaient selon le paramètre modifié et le type de cri présenté. Nos résultats suggèrent donc que, chez le diamant mandarin, le NCM est impliqué dans le codage du cri de distance. Cependant, ils mettent en évidence des différences dans ce codage entre les mâles et les femelles. Chez les femelles, ce codage permet de discriminer entre les cris d’individus connus et ceux d’individus inconnus alors que chez les mâles, son rôle reste à être déterminé. Chez les femelles, l’expérience sociale au travers de la mémorisation des signaux de communication des individus peut donc façonner les propriétés fonctionnelles des neurones d’une aire auditive secondaire. Ces propriétés pourraient donc continuellement subir des changements pour s'adapter à l’environnement social de l’individuHow sensory signals are encoded in the brain and whether their behavioural relevance affects their encoding are central questions in sensory neuroscience. Studies have consistently shown that behavioural relevance can change the neural representation of sounds in the auditory system, but what occurs in the context of natural acoustic communication where significance could be acquired through social interaction remains to be explored. The zebra finch, a highly social songbird species that forms lifelong pair bonds and uses a vocalization, the distance call, to identify its mate offers an opportunity to address this issue. One auditory area in the songbird telencephalon, the caudo-medial nidopallium (NCM) that is considered as being analogous to the secondary mammalian auditory cortex, has recently emerged as part of the neural substrate for sensory representation of species-specific vocalizations: the activation of NCM neurons is greatest when birds are exposed to conspecific song, as compared to heterospecific song or artificial stimuli. This led us to investigate whether, in the zebra finch, NCM neurons could contribute to the discrimination among vocalizations that differ in their degree of familiarity: calls produced by the mate, by familiar individuals (males or females), or by unfamiliar individuals (males or females). In females, behaviourally relevant calls, i.e. the mate’s call and familiar calls, evoked responses of greater magnitude than unfamiliar calls. This distinction between responses was seen both in multiunit recordings from awake freely moving mated females (using a telemetric system) and in single unit recordings from anesthetized mated females. In contrast, control females that had not heard them previously displayed response of similar magnitude to call stimuli. In addition, more cells showed highly selective responses in mated than in control females suggesting that experience-dependent plasticity in call-evoked responses resulted in enhanced discrimination of auditory stimuli. In males, as in females, call playback evoked robust auditory responses. However, neurons in males did not appear capable of categorizing the calls of individuals (males or females) as ‘‘familiar’’ or ‘‘unfamiliar’’. Then, we investigated how calls are represented in the NCM of zebra finches by assessing whether certain call-specific acoustic cues drove NCM neurons to a greater degree than others. Behavioural studies had previously identified call-specific acoustic cues that are necessary to elicit a vocal response from male and female zebra finches. Single-unit recordings indicated that NCM neurons in females were particularly sensitive to call modifications in the spectral domain: suppressing the fundamental frequency of call stimuli or modifying the relative energy levels of harmonics in call caused a marked decrease in response magnitude of NCM neurons. In males, NCM neurons also appear to be sensitive to call modifications in the spectral domain, however changes in magnitude of responses (increase or decrease) depended on the acoustic cue that had been modified.Our results provide evidence that the NCM is a telencephalic auditory region that contributes to the processing of the distance call, in females as well in males. However, how the distance call is processed and represented in the NCM appears to differ between males and females. In females, the NCM could be involved in dicrimination between call stimuli whereas, in males, its functional role in call-processing remains to be determined. Our results also suggest that, in females, social experience with the call of individuals, by affecting the degree to which neurons discriminated between these calls, may shape the functional properties of neurons in a telencephalic auditory area. The functional properties of auditory neurons may therefore change continuously to adapt to the social environment
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Ortiz, Cantin. "Neuronal discrimination of visual environments differentially depends on behavioural context in the hippocampus and neocortex". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS311.
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Créer des souvenirs de son environnement est une aptitude fondamentale à la survie, pour trouver de la nourriture, un abri ou échapper à des prédateurs. Pour former des souvenirs spatiaux, il faut générer une carte mentale de l'espace, appelée carte cognitive. On pense que ces cartes apparaissent dans CA1, la couche de sortie de l'hippocampe, une région du cerveau cruciale pour former de nouveaux souvenirs épisodiques. Pour utiliser des souvenirs spatiaux, il faut savoir si un environnement a déjà été visité. Cela nécessite de différencier des environnements qui peuvent paraître similaires mais sont pourtant distincts. Le gyrus denté (DG), la couche d'entrée de l'hippocampe, semble jouer un rôle fondamental pour cela. En effet, il génère des représentations neuronales fortement décorrélées, même lorsque les signaux d'entrée présentent un haut degré de similitude. Avant d'atteindre l'hippocampe, les représentations visuelles se forment dans le cortex visuel primaire (V1). V1 est traditionnellement considéré comme une région qui représente des caractéristiques visuelles de bas niveau, telles que l'orientation et la longueur de barres. Cependant, des recherches récentes ont démontré que, aussi tôt dans le flux sensoriel, les représentations neuronales sont déjà modulées par le comportement et des représentations spatiales émergent.Les distinctions entre ces deux régions étant plus complexes qu'on ne le pensait, nous nous sommes demandé comment elles pouvaient contribuer de manière différenciée au traitement sensoriel. Notre hypothèse est que les cortex sensoriels primaires fournissent une représentation fidèle de l'environnement sensoriel aux autres régions, tandis que l'hippocampe produit une carte cognitive pondérée en fonction de la pertinence comportementale des entrées sensorielles. Pour tester cette hypothèse, nous avons cherché à déterminer comment les stimuli sensoriels complexes dépendent différemment du contexte comportemental dans le V1, le DG et CA1. Nous avons utilisé l'imagerie calcique à deux photons pour enregistrer l'activité neuronale de souris maintenues par la tête et navigant dans un couloir linéaire en réalité virtuelle. Les souris ont été exposées à différents environnements en changeant les textures visuelles le long du couloir virtuel. Pendant la navigation active, les mouvements dans l'environnement virtuel étaient contrôlés par la course de l'animal sur une roue. En revanche, dans la condition, la scène visuelle était complètement découplée des mouvements de l'animal.Nous avons montré que les environnements pouvaient être différenciés à partir de l'activité de neurones uniques dans toutes les régions pendant la navigation active. Dans la condition passive, la discrimination restait élevée dans V1 tandis que dans l'hippocampe elle chutait au niveau de la chance. Un décodeur entraîné à prédire l'environnement visité à partir de l'activité de tous les neurones a révélé que la discrimination au niveau de la population était similairement affectée par le contexte comportemental. En outre, nos résultats indiquent que le degré de discrimination est corrélé avec la vitesse de course dans l'hippocampe, mais pas dans V1. Cela suggère que l'hippocampe dépend davantage du comportement que V1.Nous avons donc conclu que l'engagement dans la tâche est nécessaire pour la discrimination neuronale dans l'hippocampe, alors que cela n'exerce qu'une influence dans V1. Cela suggère que les cortex sensoriels primaires servent de discriminateurs généraux robustes des entrées sensorielles, tandis que l'hippocampe discrimine sélectivement les entrées pertinentes pour le comportement. Dans l'ensemble, ces résultats révèlent comment les informations sur l'environnement sont traitées de manière différenciée lorsqu'elles sont transmises à l'hippocampe avec des implications fondamentales pour notre compréhension de la manière dont le cerveau filtre l'information au fur et à mesure qu'elle est mise à disposition de l'hippocampeForming memories of the environment is essential for survival, whether it is for finding food, escaping predators or seeking shelter. To create spatial memories, one first needs to generate a mental representation of the surroundings, which is referred to as a cognitive map. Such maps are believed to emerge in the hippocampus, a brain region known to play a crucial role in the formation of new episodic memories, and more specifically in its output layer CA1. To efficiently use spatial memories, it is necessary to be able to ascertain whether a location has already been visited. This requires discriminating between potentially similar yet distinct sensory environments. It is thought that the dentate gyrus (DG), the entry layer of the hippocampus, plays a pivotal role in this ability. Indeed, it has been shown to perform neuronal pattern separation by creating decorrelated neuronal representations of its inputs, even when they share a high degree of similarity. Before reaching the hippocampus, sensory signals are initially processed in sensory cortices. Visual representations are formed in the primary visual cortex (V1), which is situated at the earliest stage of the neocortical hierarchy. V1 has traditionally been thought of as a brain region that represents low-level visual features, such as bars of a specific orientation or length. However, recent research has demonstrated that neuronal activity is already behaviourally modulated at this initial level of visual processing, with spatial representations emerging concurrently.Considering the growing evidence that the distinctions between these two regions are more complex than previously thought, we wondered how they may differentially contribute to sensory processing. We hypothesised that primary sensory cortices provide a faithful representation of the sensory environment to distributed brain regions, whereas the hippocampus produces a cognitive map that is weighted according to the behavioural relevance of the sensory inputs. To test this hypothesis, we aimed to determine how complex sensory stimuli differentially depend on the behavioural context in V1, CA1 and DG. We performed two-photon calcium imaging of head fixed mice navigating in a virtual-reality linear track. Mice were exposed to alternating environments by changing visual textures along the virtual corridor. During active navigation, movements in the virtual environment were controlled by the animal motion on a running wheel. By contrast, in a passive open-loop condition, the visual scene was completely uncoupled from animal locomotion.We found that environments could be discriminated based on the activity of single neurons in all regions during active navigation. However, while neurons in V1 maintained a high level of discrimination in the passive exposure condition, those in the hippocampus failed to discriminate between environments. A decoder trained to predict the visited corridor based on the activity of all neurons revealed that the discrimination at the population level was similarly affected by the behavioural context. Moreover, the results indicated that the degree of discrimination correlated with running speed in the hippocampus, but not in V1, which further supports the idea that neuronal activity is more dependent on the current behaviour in the hippocampus than in V1.We concluded that task engagement is therefore necessary for neuronal discrimination in the hippocampus, while it simply modulates it in V1, suggesting that primary sensory cortices serve as robust general-purpose discriminators of sensory inputs, while the hippocampus selectively discriminates behaviourally relevant inputs. Overall, these results reveal how information about the environment is differentially processed as it is transmitted to the hippocampus, with fundamental implications for our understanding of how the brain filters information as it is made available to the memory circuits in the hippocampus
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Ménardy, Fabien. "Reconnaissance des signaux de communication chez le diamant mandarin : étude des réponses des neurones d'une aire auditive secondaire". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00764923.
Texto completo da fonteResumo:
A l'heure actuelle, il reste largement à étudier comment le codage sensoriel des signaux vocaux de communication contribue à leur détection et à leur reconnaissance. Peu d'études se sont, en effet, penchées sur le codage des vocalisations au niveau des régions auditives en fonction de l'individu qui les produit et du degré de familiarité avec cet individu. Dans ce cadre, les oiseaux chanteurs sont un bon modèle parce qu'ils utilisent des vocalisations pour interagir et reconnaître leurs congénères et qu'ils possèdent, de plus, un ensemble de régions auditives. Parmi ces régions, le nidopallium caudomedian (NCM), une aire auditive analogue du cortex auditif secondaire chez les mammifères, est actuellement considérée comme une région spécialisée dans le traitement des vocalisations (chants et cris) de l'espèce : les neurones du NCM répondent plus fortement aux vocalisations de l'espèce qu'à celles d'une autre espèce. À partir de là, parce que chez le diamant mandarin, le cri de distance permet aux individus, mâles ou femelles, de reconnaître leur partenaire sexuel, nous avons cherché à savoir si, chez les femelles comme chez les mâles, les neurones du NCM montraient une discrimination dans leurs réponses auditives entre le cri d'individus connus (parmi lesquels figurait le partenaire sexuel) et ceux d'individus inconnus et si ces réponses reflétaient le degré de familiarité de ces vocalisations. Les enregistrements de l'activité des neurones du NCM, chez des diamants mandarins vigiles (grâce à un système de télémétrie) ou anesthésiés, lors de la présentation de cris de distance, ont révélé, chez les femelles vivant en couple et ayant été familiarisées avec un autre couple de diamants mandarins, une plus forte augmentation de l'activité lors de la diffusion des cris d'individus connus, mâles ou femelles, qu'aux cris d'individus inconnus. Une telle augmentation n'a pas été, en outre, observée chez des femelles contrôles qui n'avaient jamais entendu ces mêmes cris auparavant. De plus, ils ont indiqué que le nombre de neurones montrant un fort degré de sélectivité ainsi que la quantité d'information portée par les trains de potentiels d'action étaient plus importants chez les femelles vivant en couple que chez les femelles contrôles. En revanche, chez les mâles, bien que la plupart des neurones montrait des réponses lors de la diffusion des cris, aucune différence n'a été mise en évidence entre les cris d'individus connus et ceux d'inconnus. Nous avons alors cherché à savoir comment, d'un point de vue acoustique, les cris de distance étaient représentés au sein du NCM. En se basant sur une étude comportementale ayant déterminé quelles étaient les caractéristiques acoustiques qui contribuaient à la reconnaissance de ces cris, nous avons cherché à savoir si les neurones du NCM étaient sensibles à ces mêmes caractéristiques acoustiques. Les résultats ont montré que, chez les femelles, la suppression de la fréquence fondamentale et la modification du timbre du cri du partenaire sexuel ou du propre cri de l'oiseau provoquaient une forte diminution des réponses au sein du NCM alors que, chez les mâles, les réponses variaient selon le paramètre modifié et le type de cri présenté. Nos résultats suggèrent donc que, chez le diamant mandarin, le NCM est impliqué dans le codage du cri de distance. Cependant, ils mettent en évidence des différences dans ce codage entre les mâles et les femelles. Chez les femelles, ce codage permet de discriminer entre les cris d'individus connus et ceux d'individus inconnus alors que chez les mâles, son rôle reste à être déterminé. Chez les femelles, l'expérience sociale au travers de la mémorisation des signaux de communication des individus peut donc façonner les propriétés fonctionnelles des neurones d'une aire auditive secondaire. Ces propriétés pourraient donc continuellement subir des changements pour s'adapter à l'environnement social de l'individu.
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Alzaher, Mariam. "Mismatch negativity, un marqueur neuronal de la plasticité spatiale auditive chez les sujets sourds unilatéraux". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30253.
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Cette thèse évalue les différentes fonctions d'audition spatiale chez 3 types de populations : Normaux entendants (NE), sourds unilatéraux (SU) et sourds bilatéraux (SB). Afin de découvrir les mécanismes qui soulignent les stratégies spatio-auditives adaptative qui sont observés chez les SU avec surdité acquise. Le but principal de la thèse est de vérifier si la MMN pourrait être un marqueur neuronal de la plasticité spatiale auditive observée chez les patients SU, et de vérifier se les corrélats neuronaux sont cohérentes avec les performances spatiales auditives. Deux types d'investigations ont été appliqués sur 20 sujets NE, 21 SU et 14 SB. La première investigation s'agit d'un test d'identification de source sonore mesuré par l'erreur quadratique moyenne (RMS). La deuxième évaluation est une étude électroencéphalographie qui sert à analyser la MMN. La MMN étant défini comme un potentiel évoqué qui reflète la capacité du cerveau à détecter un changement dans les propriétés physiques d'un son. Nous avons utilisé un son standard dans une position de référence (50°) avec 3 déviation par rapport au standard (10°, 20° et 100°) dans des conditions binaurales et monaurales. Les sujets sourds unilatéraux ont été divisé en 3 groupes selon leur performance spatiale. Le groupe des bons performeurs (SU low rms) a montré des meilleurs scores RMS en comparaison avec les NE munie d'un bouchon d'oreille (NE-mon), avec des performances similaires à ceux des sujets NE en binaurale. Une augmentation progressive de la MMN avec l'angle de la déviation par rapport au standard a été noté chez tous les groupes. Avec une réduction importante de la MMN chez les NH en monaurale quand le bouchon a été appliqué du côté du standard. La MMN a montré des résultats cohérents avec nos observations comportementales, ou les sujets SU avec un bon score RMS avait également des amplitudes de la MMN plus importantes que celles des sujets NE en condition monaurale et similaires à celles des NE en condition binaurale. Les sujets SU possèdent des stratégies adaptatives saptio-auditives. Notre étude a pu démontré que la plasticité corticale spatio-auditive qui a lieu suite à la surdité est reflété par la MMN. Les observations neuronales (MMN) sont corrélées avec les observations comportementaux de localisation spatiale. Ce qui signifie que la plasticité corticale qui a lieu chez ces sujets, n'est pas limités aux fonctions d'identification de la source sonores, mais dépasse ces capacités vers des mécanismes plus complexes tel que la détection de déviation et la mémoire à court terme, qui interviennent dans la fonction de discrimination spatiale des sonsThis thesis investigates different spatial hearing functions in 3 types of populations: Normal Hearing Subjects (NHS), Unilateral Hearing Loss patients (UHL) and Bilateral Hearing Loss patients ( BHL). To discover the mechanisms underlying the adaptive strategies that are observed in UHL with acquired deafness. The main aim of the thesis is to verify whether spatial Mismatch Negativity (MMN) could be a neuronal marker of spatial auditory plasticity observed in UHL patients, and to verify whether these neural correlates are consistent with the spatial auditory performance. Two types of investigations were applied to 20 NHS, 21 UHL and 14 BHL. The first investigation is a sound source identification task measured by the root mean square error (RMS). The second assessment is an electroencephalography (EEG) study where we analyzed the amplitude and latency of the MMN. MMN is defined as an auditory evoked potential that reflects the brain's ability to detect a change in one physical property of a sound. We used a standard sound in a reference position (50°) with three deviations from the standard (10° , 20°, and 100°), in binaural and monaural conditions. UHL patients were divided into 3 groups according to their spatial performances. The group of good performers (UHL {low rms}) showed better RMS scores in comparison with NHS with earplugs (NHS-mon), with performances similar to those of NHS subjects in binaural condition. A progressive increase of the MMN with the angle of deviation from the standard was noted in all groups. With a significant reduction of MMN amplitude in monaural NHS when the ear plug was applied on the ipsilateral side of the standard. MMN showed consistent variation with the behavioral observations, where UHL {low rms} patients had larger MMN amplitudes than those of monaural NHS and similar to those of binaural NHS. UHL patients have adaptive spatial auditory strategies. Our study was able to demonstrate that spatial auditory plasticity that occurs after deafness can be reflected by the MMN. Neural observations (i.e. the MMN) are correlated with behavioral observations of spatial source identification. This means that the spatial cortical plasticity, that took place in these subjects, is not limited to the functions of identification of the sound source, but exceeds these capacities towards more complex mechanisms such as deviance detection and short-term memory, that are involved in the spatial discrimination function
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Pernot, Etienne. "Choix d'un classifieur en discrimination". Paris 9, 1994. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1994PA090014.
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Dans cette thèse, nous nous posons le problème de la détermination du classifieur le plus adapté à résoudre un problème donné de discrimination. Le choix du classifieur est déjà guidé par des contraintes opérationnelles, mais au-delà de ces contraintes, et après que le classifieur a été configuré grâce à une base d'apprentissage, c'est le taux de généralisation du classifieur (ou taux de réussite) qui est le critère caractérisant sa performance. Ce taux, généralement inconnu, est estimé à l'aide d'une base de généralisation. Cette estimation dépend donc du problème de discrimination étudié, du classifieur utilisé, de la base d'apprentissage et de la base de généralisation. Ces différentes dépendances sont étudiées soit théoriquement, soit de manière expérimentale, sur une douzaine de classifieurs différents, neuronaux et classiques. Le problème de la validité de la comparaison de deux classifieurs par les estimations de leur taux de généralisation est aussi étudié, et nous obtenons des informations sur les tailles relatives à donner aux bases d'apprentissage et de généralisation. Dans un objectif de comparaison de classifieurs, Neuroclasse, un outil logiciel donnant la possibilité de tester un grand nombre de classifieurs différents, a été développé, et est précisément décrit. Dans Neuroclasse est aussi intégré un système pour la détermination automatique du classifieur fournissant le meilleur taux de généralisation estimé sur une base de généralisation fixée. Ce système est implanté sous forme d'un système expert. Ce système, testé sur différentes bases de données, donne de bons résultats, mais met en évidence un phénomène d'apprentissage de la base de généralisation, dû aux tests successifs de nombreux classifieurs sur une même base de généralisation. Nous étudions ce phénomène expérimentalement, et nous donnons un ordre de grandeur du nombre de classifieurs qu'il est possible de tester en limitant cet effet
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Meisel, Joshua D. (Joshua Daniel). "The genetic, neuronal, and chemical basis for microbial discrimination in Caenorhabditis elegans". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104172.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Discrimination among pathogenic and beneficial microbes is essential for host organism immunity and homeostasis. Increasingly, the nervous system of animals is being recognized as an important site of bacterial recognition, but the molecular mechanisms underlying this process remain unclear. Chapter One discusses how the nematode Caenorhabditis elegans can be used to dissect the genetic and neuronal mechanisms that coordinate behavioral responses to bacteria. In Chapter Two, we show that chemosensory detection of two secondary metabolites produced by Pseudomonas aeruginosa modulates a neuroendocrine signaling pathway that promotes C. elegans avoidance behavior. Specifically, secondary metabolites phenazine- I -carboxamide and pyochelin activate a G protein-signaling pathway in the ASJ chemosensory neuron pair that induces expression of the neuromodulator DAF-7/TGF-[beta]. DAF-7, in turn, activates a canonical TGF-P signaling pathway in adjacent interneurons to modulate aerotaxis behavior and promote avoidance of pathogenic P. aeruginosa. This chapter provides a chemical, genetic, and neuronal basis for how the behavior and physiology of a simple animal host can be modified by the microbial environment, and suggests that secondary metabolites produced by microbes may provide environmental cues that contribute to pathogen recognition and host survival. Genetic dissection of neuronal responses to bacteria in C. elegans can also lend insights into neurobiology more generally. In Chapter Three we show that loss of the lithium-sensitive phosphatase bisphosphate 3'-nucleotidase (BPNT-1) results in the selective dysfunction of the ASJ chemosensory neurons. As a result, BPNT- 1 mutants are defective in behaviors dependent on the ASJ neurons, such as pathogen avoidance and dauer exit. Acute treatment with lithium also causes reversible dysfunction of the ASJ neurons, and we show that this effect is mediated specifically through inhibition of BPNT-1. Finally, we show that lithium's selective effect on the nervous system is due in part to the limited expression of the cytosolic sulfotransferase SSU-1 in the ASJ neuron pair. Our data suggest that lithium, through inhibition of BPNT- 1 in the nervous system, can cause selective toxicity to specific neurons, resulting in corresponding effects on behavior of C. elegans. In Chapter Four I discuss the future directions for the genetic dissection of pathogen recognition in C. elegans.
by Joshua D. Meisel.
Ph. D.
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Ahn, Sungwoo. "Transient and Attractor Dynamics in Models for Odor Discrimination". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1280342970.
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Zhu, Wenhua. "Modèles statistiques et réseaux de neurones : stratégie et validation dans le cas de la discrimination". Paris 9, 1995. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1995PA090022.
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Cette thèse a abordé deux grands thèmes : analyse des données et réseau de neurones. Elle présente les principales méthodes de l'analyse discriminante et traite des aspects importants de ce domaine : procédure d'apprentissage, construction et validation de règle de décision, sélection du meilleur modèle, liaisons avec des réseaux de neurones multicouches. La thèse a développé certaines techniques pour améliorer la qualité de l'apprentissage et pour réduire la complexité du réseau de neuronesThis thesis has accost two domains : data analysis and neural networks. It present the mains methods of discriminant analysis and treats the importants points in this field : learning procedures, construction and validation of decision rule, model selection, the relation with neural networks. This thesis propose some strategy of improving their generalization abilities and for reduce their complexity so that the neural networks can be applied to large more and realistic tasks
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Dahlquist, Clara. "Somatosensory system; touch : Physiology and Neuronal Correlates of Discriminative and Affective Touch". Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-9718.
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This essay is about the somatosensory system, which is divided into different kinds of touch. Described briefly are the proprioceptive touch, which is transported to the brain via A-alfa fibers and transmits information about e. g. limb position and movement. The cutaneous touch is the main focus and it is divided into discriminative touch and affective touch. The first corresponds to stimuli such as vibration and pressure and is transported via A-beta axons. The second, affective touch, corresponds to e.g. painful and pleasant stimuli which are transported to the brain via A-delta and C-fibers. The aim of the essay is to give an overview of the sense of touch, by doing a literature search, including a discussion of relevant neuronal correlates focusing particularly on affective touch. Moreover, the physiological aspects of touch will be presented. The sources that are used are review and original articles taken from databases such as ScienceDirect, and some articles send by the author. Some books have also been used to find more general knowledge. The conclusion for the essay is that touch is important for humans to function in everyday life. Additional, a specific receptor called C- tactile (CT) is identified to correspond to gentle touch and is suggested to have a vital role for humans in maintaining and forming social bounds. Moreover, discriminative touch is associated with activation in the primary and secondary somatosensory cortex, whereas affective touch seems to be associated with activity in the orbitofrontal cortex, cingulate cortex and the insula cortex, as well as the prefrontal cortex, which is suggested to be activated during interpersonal touch. Further, the sense touch needs to be more researched in order to understand its functions and benefits deeper.
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Derosiere, Gérard. "Vers la discrimination des corrélats neuronaux des déficits d'attention : des Neurosciences Cognitives à l'Ingénierie Cognitive". Thesis, Montpellier 1, 2014. http://www.theses.fr/2014MON1T008/document.
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L'attention focalisée est une fonction cognitive de haut niveau permettant à l'Homme de faciliter sélectivement certaines actions et perceptions. Dans un monde regorgeant de choix d'actions, et de possibilités de perceptions, l'attention focalisée représente une composante vitale de la cognition humaine. Un constat important doit cependant être noté : l'Homme est incapable de maintenir indéfiniment un état stable d'attention focalisée. Cette incapacité est mise en évidence pendant les tâches d'attention soutenue par l'apparition progressive de déficiences sensori-motrices au cours du temps. L'impulsivité motrice augmente alors, ainsi que le temps de réponse aux stimuli impératifs, et la sensibilité perceptive diminue. À l'heure actuelle, les bases neuronales du phénomène restent très peu connues et ce manque de connaissance est clairement perceptible au sein de deux champs disciplinaires - les Neurosciences Cognitives et l'Ingénierie Cognitive. En Neurosciences Cognitives, la question demeure ainsi posée : pourquoi l'Homme est-il incapable de maintenir un niveau de performance sensori-motrice optimal au cours de tâches d'attention soutenue ? En Ingénierie Cognitive, la problématique concerne le développement d'Interfaces Cerveau-Machine (ICM) passives : identifier les marqueurs neuronaux des déficits d'attention permettrait, à terme, de suivre en temps réel l'état cognitif de l'Homme et de l'alerter de la survenue de ces déficits durant son activité. Ces deux problématiques ont été traitées dans cette thèse. Dans un premier temps, je démontre que le maintien d'une attention focalisée sur une stimulation visuelle entraîne une rapide inhibition des aires visuelles corticales. Cette inhibition sensorielle serait liée à l'absence de variation de la stimulation sensorielle. Ainsi, l'inhibition sensorielle serait bénéfique au cours de tâches de recherche visuelle : elle permettrait à l'Homme d'éviter de réexaminer plusieurs fois le même stimulus, le même objet, la même localisation spatiale; mais lorsqu'une attention soutenue est requise, ce mécanisme serait alors à l'origine de l'apparition de déficiences sensorielles. La présence de cette inhibition sensorielle apporte une explication probante à la diminution de sensibilité perceptive et à l'allongement du temps de réaction qui caractérisent le phénomène. Je montre ensuite que l'activité de structures neuronales motrices et d'aires corticales connues pour sous-tendre l'attention focalisée (i.e., tractus cortico-spinal, et aires corticales motrice primaire, préfrontale et pariétale droite) augmente progressivement au cours d'une tâche d'attention soutenue. Ce sur-engagement reflèterait un processus de compensation en réponse au désengagement préalable des aires corticales sensorielles et à la diminution de la qualité des représentations perceptives. Aussi, l'augmentation d'activité des structures neuronales motrices expliquerait l'augmentation de l'impulsivité motrice, une des signatures comportementales des déficits d'attention. Dans un second temps, je teste la possibilité d'exploiter ces corrélats neuronaux des déficits d'attention afin de discriminer deux états attentionnels donnés (i.e., avec ou sans déficits d'attention) au sein d'une ICM passive. Nous avons pour cela appliqué des méthodes de classification supervisées sur des données de spectroscopie proche infra-rouge reflétant l'activité hémodynamique des aires corticales préfrontale et pariétale enregistrées pendant une tâche d'attention soutenue. Nous rapportons des résultats encourageant en termes de performance de classification pour le futur développement d'ICM passives. Pris ensemble, les résultats décrits dans cette thèse apportent une meilleure compréhension des corrélats neuronaux des déficits d'attention et montrent comment cette connaissance peut être exploitée afin de développer des systèmes permettant de limiter la survenue d'accidents et d'incidents liés à l'erreur humaine dans un contexte écologiqueFocused attention represents a high-level cognitive function enabling humans to selectively facilitate specific actions and perceptions. In a world full of choices of action, and of perceptual possibilities, focused attention appears to be a vital component of human cognition. One observation however, is worth making: human-beings are unable to maintain stable states of focused attention indefinitely. This inability manifests during sustained attention tasks with the progressive occurrence of sensory-motor deficiencies with time-on-task. The phenomenon - called attention decrement - is characterized by increases in motor impulsivity and in response times to imperative events, and by a reduction in perceptual sensitivity. So far, the neural underpinnings of attention decrement have not been fully elucidated and this lack of knowledge is clearly palpable within two disciplinary fields : Cognitive Neuroscience and Cognitive Engineering. In Cognitive Neuroscience, the associated question is why are human-beings unable to maintain an optimal sensory-motor performance during sustained attention tasks? In Cognitive Engineering, the lack of a complete scientific understanding of attentional issues impacts the development of efficient passive Brain-Computer interfaces (BCI), capable of detecting the occurrence of potentially dangerous attention decrements during the performance of everyday activities. Both issues have been addressed in this thesis. In terms of Cognitive Neuroscience, I demonstrate that sustaining focused attention on a visual stimulation rapidly leads to an inhibition of the visual cortices. This sensory inhibition can be causally related to the lack of changes in perceptual stimulation typically characterizing sustained attention tasks. While the mechanism may be beneficial during visual search tasks as it helps humans avoid processing the same stimulus, the same object, the same location several times, it can lead to the occurrence of sensory deficiencies when sustained attention is required. As such, the sensory inhibition provides a compelling explanation as to the decrease in perceptual sensitivity and to the increase in reaction time that typify attention decrement. I show in a second study that attention decrement is associated with an increase in the activity of motor- and attention-related neural structures (i.e., cortico-spinal tract, primary motor, prefrontal and right parietal cortices). This excessive engagement reflects a compensatory process occurring in response to the sensory disengagement already highlighted and to the related degradation of the quality of perceptual representations. It is notable that the excessive engagement of the motor neural structures with time-on-task provides a potential explanation for the increase in motor impulsivity typifying attention decrement. In terms of application of these new findings, I investigated the potential of exploiting these neural correlates of attention decrement to discriminate between two different attentional states (i.e., with or without attention decrement) through a passive BCI system. To do so, we applied supervised classification analyses on near-infrared spectroscopy signals reflecting the hemodynamic activity of prefrontal and parietal cortices as recorded during a sustained attention task. We achieved relatively promising classification performance results which bode well for the future development of passive BCI. When considered together, the results described in this thesis contribute towards a better understanding of the neural correlates of attention decrement and demonstrate how this novel knowledge can be exploited for the future development of systems which may enable a reduction in accidents and human error-driven incidents in real world environments
Livros sobre o assunto "Discrimination neuronale"
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Clark, Kelsey L., Behrad Noudoost, Robert J. Schafer e Tirin Moore. Neuronal Mechanisms of Attentional Control. Editado por Anna C. (Kia) Nobre e Sabine Kastner. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199675111.013.010.
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Covert spatial attention prioritizes the processing of stimuli at a given peripheral location, away from the direction of gaze, and selectively enhances visual discrimination, speed of processing, contrast sensitivity, and spatial resolution at the attended location. While correlates of this type of attention, which are believed to underlie perceptual benefits, have been found in a variety of visual cortical areas, more recent observations suggest that these effects may originate from frontal and parietal areas. Evidence for a causal role in attention is especially robust for the Frontal Eye Field, an oculomotor area within the prefrontal cortex. FEF firing rates have been shown to reflect the location of voluntarily deployed covert attention in a variety of tasks, and these changes in firing rate precede those observed in extrastriate cortex. In addition, manipulation of FEF activity—whether via electrical microstimulation, pharmacologically, or operant conditioning—can produce attention-like effects on behaviour and can modulate neural signals within posterior visual areas. We review this evidence and discuss the role of the FEF in visual spatial attention.
Capítulos de livros sobre o assunto "Discrimination neuronale"
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Steinmetz, Michael A., Ranulfo Romo e Vernon D. Mountcastle. "Cortical Neuronal Mechanisms for Frequency Discrimination in the Somesthetic Sense of Flutter". In Information Processing in the Somatosensory System, 289–303. London: Macmillan Education UK, 1991. http://dx.doi.org/10.1007/978-1-349-11597-6_21.
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Feng, Albert S., e Theodore H. Bullock. "Neuronal Mechanisms for Object Discrimination in the Weakly Electric Fish Eigenmannia Virescens". In How do Brains Work?, 233–50. Boston, MA: Birkhäuser Boston, 1993. http://dx.doi.org/10.1007/978-1-4684-9427-3_25.
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Perez-Uribe, Andres, e Héctor F. Satizábal. "Artificial Neural Networks and Data Compression Statistics for the Discrimination of Cultured Neuronal Activity". In Artificial Neural Networks and Machine Learning – ICANN 2012, 201–8. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-33269-2_26.
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THUNBERG, J., F. HELLSTRÖM, M. BERGENHEIM, J. PEDERSEN e H. JOHANSSON. "NEURONAL CODING AND MOVEMENT DISCRIMINATION IN PROPRIOCEPTION". In Neuronal Coding Of Perceptual Systems, 263–67. WORLD SCIENTIFIC, 2001. http://dx.doi.org/10.1142/9789812811899_0021.
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N.S. Sampaio, Pedro, e Carla Brites. "Near-Infrared Spectroscopy and Machine Learning: Analysis and Classification Methods of Rice". In Rice [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99017.
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Nowadays, the conventional biochemical methods used to differentiate and characterize rice types, biochemical properties, authentication, and contamination issues are difficult to implement due to the high cost of reagents, time requirement and environmental issues. Actually, the success of agri-food technology is directly related to the quality of analysis of experimental data acquired by sensors or techniques such as the infrared-spectroscopy. To overcome these technical limitations, a rapid and non-destructive methodology for discrimination and classification of rice has been investigated. Near-infrared spectroscopy is considered as fast, clean, and non-destructive analytical tools and its spectra present significant biomolecular information that must be analysed by sophisticated methodologies. Machine learning plays an important role in the analysis of the spectral data being used several methods such as Partial Least Squares, Principal Component Analysis, Partial Least Squares-Discriminant Analysis, Support Vector Machine, Artificial Neuronal Network, among others which can successfully be applied for food classification and discrimination as well as in terms of authentication and contamination issues. The quality control of rice is extremely important at every stage of production, beginning with estimation of raw agricultural materials and monitoring their quality during storage, estimating food quality during the production process and of the final products as well as the determination of their authenticity and the detection of adulterants.
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Marrow, Jocelyn, e T. M. Luhrmann. "Conclusion". In Our Most Troubling Madness. University of California Press, 2016. http://dx.doi.org/10.1525/california/9780520291089.003.0014.
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Schizophrenia is a disorder with causes that are endogenous to the body including genetic vulnerability and the decay of neuronal connections. However, there is evidence that individual vulnerability to psychosis is increased by the experiences of discrimination, despair, trauma, and failure. Drawing upon epidemiology and animal biology, this chapter argues that repeated social defeat increases the risk of developing psychosis. Further, social defeat, especially in the United States, is a regular experience of those who who live with a serious mental illness. The case studies of persons with psychosis in this volume illustrate the social and cultural factors that may be responsible for outcomes. How psychosis is understood, whether available work can accommodate the ill individual, the type of family involvement, the social and cultural backdrop, and the meaning of symptoms are factors that mitigate or exacerbate illness. The final section of this chapter presents some recommendations for how the lives of those with psychosis might be improved.
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Fagan, Anne M. "Fluid Biomarkers for Alzheimer’s Disease". In Neurobiology of Mental Illness, editado por David M. Holtzman, 834–43. Oxford University Press, 2013. http://dx.doi.org/10.1093/med/9780199934959.003.0063.
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Dementia due to Alzheimer’s disease (AD) is estimated to reach epidemic proportions by the year 2030. Given the limited accuracy of current clinical diagnosis, biomarkers of AD pathologies are being sought. Reductions in cerebrospinal fluid (CSF) levels of Aβ42 (marker of amyloid plaques) and elevations in tau species (markers of neurofibrillary tangles and/or neurodegeneration) are useful for AD diagnosis and prognosis. Novel CSF and plasma/serum biomarkers are being explored to aid in discriminating AD from non-AD neurodegenerative diseases andidentifying additional AD-related processes (e.g., neuroinflammation and early neuronal stress and dysfunction). Biomarkers are being considered for use in clinical trial design and inclusion in revised diagnostic criteria for research and clinical applications. Emphasis is on early (even ‘preclinical’) detection in order to identify and applytherapies that have the best chance of preserving normal cognitive function.
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Guzmán-Ramírez, Enrique, Ayax García, Esteban Guerrero-Ramírez, Antonio Orantes Molina, Oscar Ramírez e Ignacio Arroyo. "Multi-object Recognition Using a Feature Descriptor and Neural Classifier". In Vision Sensors - Recent Advances [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106754.
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In the field of object recognition, feature descriptors have proven to be able to provide accurate representations of objects facilitating the recognition task. In this sense, Histograms of Oriented Gradients (HOG), a descriptor that uses this approach, together with Support Vector Machines (SVM) have proven to be successful human detection methods. In this paper, we propose a scheme consisting of improved HOG and a classifier with a neural approach to producing a robust system for object recognition. The main contributions of this work are: First, we propose an improved gradient calculation that allows for better discrimination for the classifier system, which consists of performing a threshold over both the magnitude and direction of the gradients. This improvement reduces the rate of false positives. Second, although HOG is particularly suited for human detection, we demonstrate that it can be used to represent different objects accurately, and even perform well in multi-class applications. Third, we show that a classifier that uses a neuronal approach is an excellent complement to a HOG-based feature extractor. Finally, experimental results on the well-known Caltech 101 dataset illustrate the benefits of the proposed scheme.
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Funder, John W. "Hormones and receptors: fundamental considerations". In Oxford Textbook of Endocrinology and Diabetes, 24–28. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199235292.003.1022.
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The original endocrine physiologists viewed hormones as responses to homoeostatic challenge, any signal a call to arms; the word is thus derived from the classical Greek ωρμαειν—‘to arouse’. In the twenty-first century a hormone is a molecule—small or large, protein or lipid—secreted in a regulated fashion from one organ and acting on another. The definition is firmly based on the anatomy of the seventeenth century, the histology of the nineteenth, and the physiology of the twentieth. It has been shaped by convention and clinical specialization: gut hormones are the marches between endocrinology and gastroenterology, and the adrenal medulla the territory of the cardiovascular physician. It has been refined by concepts of paracrine—where the secretion of one cell type in a tissue acts on another cell type in the same tissue—and autocrine, where a particular cell type both secretes and responds to a particular signal. Inherent in the concepts of paracrine and autocrine are that the signal is not secreted into blood or lymph, to be distributed more or less throughout the body, but is made locally to act locally. A very good example of a signalling system with both paracrine and autocrine activities is the neuronal synapse. Inherent in the concept of the signal is that of a receptor: a signal without a receptor is the sound of one hand clapping. Inherent in the concept of a receptor are two functions: that of being able to discriminate between different signals, and to propagate the signal by activating cell membrane or intracellular signal transduction pathways. Discrimination by a receptor between different circulating potential signals is, in the first instance, a function of the likelihood of a particular signal being able to interact with the receptor, for a period of time sufficient to alter the confirmation of the receptor and thus to trigger propagation. This interaction is commonly referred to as binding, and thus the circulating hormone as a ligand (that which is bound). If the structures of ligand and receptors are such that the initial interaction is followed by formation of strong intermolecular bonds between the two, lessening the possibility of dissociation and the receptor returning to an unliganded state, the receptor is said to have high affinity for the ligand (and vice versa). If the binding is followed by propagation of the ‘appropriate’ signal the ligand is classified as an agonist, or active hormone; if a molecule occupies the binding site on the receptor but does not so alter its structure as to propagate a signal, it is classified as a hormone antagonist (and often, by extension, a receptor antagonist). In the past couple of decades, the concepts of ‘agonist’ and ‘antagonist’ have needed to be refined, as noted subsequently in this chapter.
Trabalhos de conferências sobre o assunto "Discrimination neuronale"
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Samavat, Mohammad, Dori Luli e Sharon Crook. "Neuronal network models for sensory discrimination". In 2016 50th Asilomar Conference on Signals, Systems and Computers. IEEE, 2016. http://dx.doi.org/10.1109/acssc.2016.7869533.
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Goh, Aik, Stefan Craciun, Sudhir Rao, David Cheney, Karl Gugel, Justin C. Sanchez e Jose C. Principe. "Wireless transmission of neuronal recordings using a portable real-time discrimination/compression algorithm". In 2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2008. http://dx.doi.org/10.1109/iembs.2008.4650196.
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Metcalfe, Benjamin, Daniel Chew, Chris Clarke, Nick Donaldson e John Taylor. "An enhancement to velocity selective discrimination of neural recordings: Extraction of neuronal firing rates". In 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). IEEE, 2014. http://dx.doi.org/10.1109/embc.2014.6944528.
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Muresan, Denisa Bianca, Raluca-Dana Ciure, Eugen Richard Ardelean, Vasile Vlad Moca, Raul Cristian Muresan e Mihaela Dins. "Spike sorting using Superlets: Evaluation of a novel feature space for the discrimination of neuronal spikes". In 2022 IEEE 18th International Conference on Intelligent Computer Communication and Processing (ICCP). IEEE, 2022. http://dx.doi.org/10.1109/iccp56966.2022.10053955.
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Castro-Silupu, Wilson, Monica Saavedra-Garcia, Himer Avila-George, Miguel De la Torre-Gomora e Adriano Bruno-Tech. "Probabilistic or Convolutional-LSTM neuronal networks: a comparative study of discrimination capacity on frozen - thawed fish fillets". In 2022 11th International Conference On Software Process Improvement (CIMPS). IEEE, 2022. http://dx.doi.org/10.1109/cimps57786.2022.10035684.
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