Dissertations / Theses on the topic 'Cortex'
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Esmaeili, Vahid. "Neuronal correlates of tactile working memory in rat barrel cortex and prefrontal cortex." Doctoral thesis, SISSA, 2014. http://hdl.handle.net/20.500.11767/3869.
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The neuronal mechanisms of parametric working memory – the short-term storage of graded stimuli to guide behavior – are not fully elucidated. We have designed a working memory task where rats compare two sequential vibrations, S1 and S2, delivered to their whiskers (Fassihi et al, 2014). Vibrations are a series of velocities sampled from a zero-mean normal distribution. Rats must judge which stimulus had greater velocity standard deviation, σ (e.g. σ1 > σ2 turn left, σ1 < σ2 turn right). A critical operation in this task is to hold S1 information in working memory for subsequent comparison. In an earlier work we uncovered this cognitive capacity in rats (Fassihi et al, 2014), an ability previously ascribed only to primates. Where in the brain is such a memory kept and what is the nature of its representation?
To address these questions, we performed simultaneous multi-electrode recordings from barrel cortex – the entryway of whisker sensory information into neocortex – and prelimbic area of medial prefrontal cortex (mPFC) which is involved in higher order cognitive functioning in rodents. During the presentation of S1 and S2, a majority of neurons in barrel cortex encoded the ongoing stimulus by monotonically modulating their firing rate as a function of σ; i.e. 42% increased and 11% decreased their firing rate for progressively larger σ values. During the 2 second delay interval between the two stimuli, neuronal populations in barrel cortex kept a graded representation of S1 in their firing rate; 30% at early delay and 15% at the end. In mPFC, neurons expressed divers coding characteristics yet more than one-fourth of them varied their discharge rate according to the ongoing stimulus. Interestingly, a similar proportion carried the stimulus signal up to early parts of delay period. A smaller but considerable proportion (10%) kept the memory until the end of delay interval.
We implemented novel information theoretic measures to quantify the stimulus and decision signals in neuronal responses in different stages of the task. By these measures, a decision signal was present in barrel cortex neurons during the S2 period and during the post stimulus delay, when the animal needed to postpone its action. Medial PFC units also represented animal choice, but later in the trial in comparison to barrel cortex. Decision signals started to build up in this area after the termination of S2.
We implemented a regularized linear discriminant algorithm (RDA) to decode stimulus and decision signals in the population activity of barrel cortex and mPFC neurons. The RDA outperformed individual clusters and the standard linear discriminant analysis (LDA). The stimulus and animal’s decision could be extracted from population activity simply by linearly weighting the responses of neuronal clusters. The population signal was present even in epochs of trial where no single cluster was informative.
We predicted that coherent oscillations between brain areas might optimize the flow of information within the networks engaged by this task. Therefore, we quantified the phase synchronization of local field potentials in barrel cortex and mPFC. The two signals were coherent at theta range during S1 and S2 and, interestingly, prior to S1. We interpret the pre-stimulus coherence as reflecting top-down preparatory and expectation mechanisms.
We showed, for the first time to our knowledge, the neuronal correlates of parametric working memory in rodents. The existence of both positive and negative codes in barrel cortex, besides the representation of stimulus memory and decision signals suggests that multiple functions might be folded into single modules. The mPFC also appears to be part of parametric working memory and decision making network in rats.
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Ribenis, Aksels. "Epilepsy surgery around language cortex." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-98318.
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Rönnqvist, Oskar. "Pekskärmsanvändargränssnittsmodul till ARM Cortex-M3." Thesis, KTH, Maskinkonstruktion (Inst.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40281.
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SammanfattningDenna rapport utreder hur ett pekskärmsanvändargränssnitt kan implementeras på Syntronic AB’s hård- och mjukvaruplattform baserad på ARM Cortex-M3.Ett pekskärmsanvändargränssnitt kräver två system, ett tryckkänsligtsystem för att detektera och positionera när användaren ger input till systemet och en skärm för att presentera ett grafiskt användargränssnitt.Rapporten börjar med att beskriva de tillgängliga teknikerna för pekpaneler och skärmar. Detta syftar till att ge djupare kunskap om de olika teknologierna och deras för- och nackdelar. Denna kunskap används sedan för att i samarbete med Syntronic AB utvärdera de olika teknologierna utifrån Syntronic AB’s krav. Utvärderingen leder till val av teknik för både pekpanel och skärm som köps in och implementeras på plattformen.Implementationen består av både hårdvarunära programmering för kommunikationen med pekpanel och skärm och API mjukvaror för att hantera hårdvaran på ett enkelt sätt.Både hård- och mjukvara är dokumenterad för att visa hur systemet är uppbyggt. Denna dokumentation skall också kunna användas som en manual till mjukvaran vid vidareutveckling eller tillämpning.Resultatet av implementationen är en pekpanel och en skärm med ett förenklat användargränssnitt. Implementationen visar tydligt hur ett pekkänsligt användargränssnitt kan se ut på plattformen och tillhandahåller mjukvara som är återanvändbar.AbstractThis report investigates how a touch sensitive user interface can be implemented on Syntronic AB’s hardware and software platform based on an ARM Cortex-M3 microcontroller.A touch sensitive user interface consists of two systems, one touch sensitive system to detect and position user input and one display to present a graphical user interface.The first part of the report describes available touch and display technologies. The purpose is to deepen the knowledge about the different technologies and their advantages and disadvantages. This knowledge is then used to evaluate the technologies in collaboration with Syntronic AB based on their needs. The evaluation leads to a choice of technology both for the touch sensitive system and display technology. Hardware corresponding to the technology choices is ordered and implemented.The implementation consists of both software that is strongly connected to the hardware to handle the communication with the touch panel and display and API software to enable easier interfacing to the hardware.Both hard- and software are documented to describe the system structure. This documentation can also be used as a software manual to ease further development or implementation.The result of the implementation is a touch panel and a display with a simple GUI. The implementation clearly shows how a touch sensitive interface can be implemented on the platform and provides software that is reusable.
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Kleppe, Ingo Christian. "Synaptic variability in the cortex." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619941.
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Thompson, P. D. "Motor cortex stimulation in man." Thesis, King's College London (University of London), 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261197.
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Jánossy, Andrea. "Régulation cholinergique du cortex surrénal." Lyon 1, 2001. http://www.theses.fr/2001LYO1T014.
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Duret, Margaux. "Organisation spatiale et temporelle de l'activité neuronale du cortex moteur chez le singe macaque dans une tâche d'atteinte et de saisie manuelle." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0408/document.
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Il est classiquement admis que le cortex moteur des primates est organisé topographiquement en lien avec le contrôle des différentes parties du corps. Il a également été suggéré que différentes zones de cette aires corticales pourraient être impliquées dans différents processus de préparation motrice. Suivant cette dernière hypothèse, cette thèse a pour objectif d’étudier les modulations spatiales et temporelles de l’activité neuronale du cortex moteur au cours de la préparation et de l’exécution de mouvements de saisie manuelle. Trois singes ont été entraînés à réaliser une tâche pré-indicée de saisie manuelle. Chez chaque animal, une matrice d’électrodes a été implantée chroniquement dans le cortex moteur. Dans une première étude, nous avons démontré que les modulations d’activité associées à différents processus préparatoires sont localisées dans différentes zones du cortex moteur. Ces zones seraient activées séquentiellement au cours de la préparation motrice suivant une alternance de phases de traitement stationnaire et de propagation dynamique. Dans une seconde étude, nous avons exploré les interactions neuronales par l’utilisation de la mesure de corrélation de variabilité (rsc) entre paires de neurones. Cette deuxième étude a fait ressortir 3 résultats principaux. Les valeurs de rsc sont plus élevées au cours de la préparation du mouvement que lors de son exécution. Elles diminuent avec la distance qui sépare les neurones. Elles sont plus importantes entre interneurones qu’entre neurones supposés pyramidaux. L’ensemble de ces observations ont été discutées en lien avec différentes modèles d’organisation spatiale des aires motrices corticalesThe motor cortex follows a somatotopic organization in which the different body parts are controlled by distinct cortical zones. It has also been proposed that different spatial zones of this cortical area could be involed in distinct processes of motor preparation. Following this latter hypothesis, the objective of this thesis is to study the spatio-temporal modulations of motor cortex activity during movement preparation and execution. Three monkeys have been trained in an instructed delayed reach-to-grasp task. In each animal, a multielectrode Utah array was chronically implanted in the motor cortex to explore the dynamic modulations of neural activity during task performance. In a first study, we demonstrated that the modulations of neural activity related to distinct processes of motor preparation occur at different cortical locations. These locations are activated sequentially during motor preparation through alternating phases of stationary processing and dynamic propagation. In a second study, we analysed the neural interactions using a measure of spike count correlation (rsc) between pair of neurons. We reported 3 main results. Correlations are higher during movement preparation than during execution. They decrease with the distance between neurons. Finally, they are higher bewteen putative interneurons than bewteen putative pyramidal neurones. All these observations are discussed in relation to several models of the spatial organization the motor cortex
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Andres, Michael. "Number and finger interactions : from the parietal to the motor cortex / Interactions entre les nombres et les doigts : du cortex pariétal au cortex moteur." Université catholique de Louvain, 2006. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-03192006-125748/.
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The observations made in brain-lesioned patients and the result of functional brain imaging studies converge to the hypothesis that the posterior parietal cortex (PPC) is involved in calculation and number processing. However, if numerical disorders generally result from a left parietal lesion, the results of some brain imaging studies suggest that the right PPC could also play a role in number magnitude processing. In order to clarify this question, we used transcranial magnetic stimulation to induce a virtual lesion of the left or right PPC in healthy subjects while they performed number comparison. Our results show that the integrity of the left PPC is a necessary condition for the precise discrimination required during close number comparison; whereas the comparison of far numbers can be performed by either hemisphere as suggested by the fact that this task is affected only by the simultaneous virtual lesion of both hemispheres. In order to better identify which processes underlie the numerical competence of the PPC, we then studied the possible interactions between number processing and visuo-motor functions. Indeed, a meta-analysis performed on functional imaging data revealed that number processing depends on parietal regions, but also on certain premotor areas, which are very close to those involved in the control of finger movements. In a first series of experiments, we thus observed an excitability increase in motor circuits during the enumeration of dots presented on a computer screen. Given that the counting task was performed with both hands at rest, this increase was interpreted as reflecting the mental simulation of pointing movements or sequential finger rising as counting goes on. In a second series of experiments, we showed that information related to number magnitude could interfere with the aperture of the finger grip required to grasp an object. These results suggest that the conformation of the hand to object size shares, with the representation of numbers, common processes for magnitude estimate. In conclusion, our thesis supports the hypothesis that our numerical capacities rely, at least partially, on visuo-motor functions involving the PPC; this could explain why the numerical capacities of the left hemisphere, which is dominant for motor activities, are more precise. / Les observations réalisées chez les patients cérébrolésés ainsi que le résultat des études d'imagerie cérébrale fonctionnelle convergent vers l'hypothèse selon laquelle le cortex pariétal postérieur (CPP) est impliqué dans le traitement des nombres et le calcul. Cependant, si les troubles du calcul résultent le plus souvent d'une lésion pariétale gauche, les résultats de certaines études d'imagerie fonctionnelle suggèrent que le CPP droit pourrait également jouer un rôle dans le traitement de la magnitude des nombres. Afin de clarifier cette question, nous avons utilisé la stimulation magnétique transcrânienne pour induire une lésion virtuelle du CPP gauche ou droit chez des sujets sains réalisant une tâche de comparaison de nombres. Nos résultats montrent que l'intégrité du CPP gauche est une condition nécessaire à la discrimination précise requise lors de la comparaison de nombres proches; la comparaison de nombres éloignés peut, quant à elle, être réalisée par l'un ou l'autre hémisphère comme le suggère le fait que cette tâche n'est affectée que par lésion virtuelle simultanée des deux hémisphères. Afin de mieux appréhender les processus sur lesquels s'appuient les compétences numériques du CPP, nous avons ensuite étudié les interactions possibles entre le traitement des nombres et les fonctions visuo-motrices. En effet, une méta-analyse réalisée sur des données d'imagerie fonctionelle a révélé que le traitement des nombres dépend de régions pariétales, mais également de certaines aires prémotrices, proches de celles impliquées dans le contrôle des mouvements des doigts. Dans une première série d'expériences, nous avons ainsi observé une augmentation de l'excitabilité des circuits moteurs lors du comptage de points présentés sur l'écran d'un ordinateur. Etant donné que la tâche de comptage était réalisée avec les mains au repos, cette augmentation a été interprétée comme le reflet d'une simulation mentale de mouvements de pointage ou d'extension séquentielle des doigts pendant le comptage. Dans une deuxième série d'expériences, nous avons montré que l'information relative à la magnitude des nombres pouvait interférer avec l'ouverture de la pince bidigitale requise pour saisir un objet. Ces résultats suggèrent que la conformation de la main adaptée à la taille des objets partage, avec la représentation des nombres, des processus communs d'estimation de la magnitude. En conclusion, notre travail supporte l'hypothèse selon laquelle nos capacités numériques pourraient, en partie du moins, reposer sur des fonctions visuo-motrices impliquant le CPP ; ceci pourrait expliquer pourquoi les capacités numériques de l'hémisphère gauche, dominant pour les activités motrices, sont plus précises.
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Nadji, Al-Husein, and Hgi Haval Sarbast. "Bearbetningstid och CPU-användning i Snort IPS : En jämförelse mellan ARM Cortex-A53 och Cortex-A7." Thesis, Tekniska Högskolan, Jönköping University, JTH, Datateknik och informatik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-50899.
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Syftet med denna studie är att undersöka hur bearbetningstiden hos Snort intrångsskyddssystem varierar mellan två olika processorer; ARM Cortex-A53 och Cortex-A7. CPU-användningen undersöktes även för att kontrollera om bearbetningstid är beroende av hur mycket CPU Snort använder. Denna studie ska ge kunskap om hur viktig en processor är för att Snort ska kunna prestera bra när det gäller bearbetningstid och CPU användning samt visa det uppenbara valet mellan Cortex-A53 och Cortex-A7 när man ska implementera Snort IPS. Med hjälp av litteratursökning konstruerades en experimentmiljö för att kunna ge svar på studiens frågeställningar. Snort kan klassificeras som CPU-bunden vilket innebär att systemet är beroende av en snabb processor. I detta sammanhang innebär en snabb processor gör att Snort hinner bearbeta den mängd nätverkstrafik den får, annars kan trafiken passera utan att den inspekteras vilket kan skada enheten som är skyddat av Snort. Studiens resultat visar att bearbetningstiden i Snort på Cortex-A53 och Cortex-A7 skiljer sig åt och en tydlig skillnad i CPU-användning mellan processorerna observerades. Studien visar även kopplingen mellan bearbetningstiden och CPUanvändning hos Snort. Studiens slutsats är att ARM Cortex-A53 har bättre prestanda vid användning av Snort IPS avseende bearbetningstid och CPU-användning, där Cortex-A53 har 10 sekunder kortare bearbetningstid och använder 2,87 gånger mindre CPU.The purpose of this study is to examine how the processing time of the Snort intrusion prevention system varies on two different processors; ARM Cortex-A53 and CortexA7. CPU usage was also examined to check if processing time depends on how much CPU Snort uses. This study will provide knowledge about how important a processor is for Snort to be able to perform well in terms of processing time and CPU usage. This knowledge will help choosing between Cortex-A53 and Cortex-A7 when implementing Snort IPS. To achieve the purpose of the study a literature search has been done to design an experimental environment. Snort can be classified as CPU-bound, which means that the system is dependent on a fast processor. In this context, a fast processor means that Snort is given enough time to process the amount of traffic it receives, otherwise the traffic can pass through without it being inspected, which can be harmful to the device that is protected by Snort. The results of the study show that the processing time in Snort on Cortex-A53 and Cortex-A7 differs and an obvious difference in CPU usage between the processors is shown. The study also presents the connection between processing time and CPU usage for Snort. In conclusion, ARM Cortex-A53 has better performance when using Snort IPS in terms of processing time and CPU usage, Cortex-A53 has 10 seconds less processing time and uses 2,87 times less CPU.
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Chavez, Candice Monique. "Top-down modulation by medial prefrontal cortex of basal forebrain activation of auditory cortex during learning." CSUSB ScholarWorks, 2006. https://scholarworks.lib.csusb.edu/etd-project/3053.
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The experiment tested the hypothesis that the acetylcholine (ACh) release in the rat auditory cortex is greater in rats undergoing auditory classical conditioning compared to rats in a truly random control paradigm where no associative learning takes place and that this is mediated by prefrontal afferent projections influencing the nucleus basalis magnocellularis (NBM), which in turn modulates ACh release in neocortex. Rats with bilateral ibotenic acid lesions of medial prefrontal and agranular insular cortices were tested in an auditory classical conditioning task while ACh was collected from the primary auditory cortex. It was hypothesized that lesions of these prefrontal areas would prevent learning-related increases of ACh release in the primary auditory cortex. The hypothesized results were supported. Results from this experiment provide unique evidence that medial prefrontal cortex projections to the NBM are important for mediating cortical ACh release during associative learning.
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Salbreux, Guillaume. "Modélisation des instabilités du cortex d'actine." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00382577.
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Le cortex d'actine est une fine couche de gel d'une épaisseur de l'ordre du micron, attaché à la membrane lipidique de la cellule. Il est constitué d'un réseau de filaments d'actine qui sont constamment polymérisés à la membrane puis dépolymérisés, dans un mouvement de « tapis roulant ». Des moteurs moléculaires, les myosines, génèrent des contraintes internes dans le gel.Le cortex contrôle ainsi les variations de forme de la cellule. Dans cette thèse nous utilisons le modèle des gels actifs pour explorer certaines propriétés du cortex d'actine. Le gel est décrit a l'échelle mésoscopique comme un matériau viscoélastique nématique dans lequel les myosines utilisent l'énergie fournie par l'hydrolyse de l'ATP pour produire des contraintes actives, c'est à dire plaçant le système hors d'équilibre thermodynamique. Dans un premier temps nous étudions de quelle façon l'épaisseur du cortex peut être régulée, et nous discutons l'apparition d'instabilités actives dans la couche. Nous utilisons l'instabilité du gel ainsi décrite pour interpréter l'observation expérimentale d'oscillations de formes de fibroblastes induites par des canaux calciques mecanosensibles. En incluant un paramètre d'ordre nématique dans notre description, nous montrons que soumettre le cortex à une concentration inhomogène de myosines doit conduire à l'apparition d'un flux de filaments et à la formation d'un anneau, ainsi qu'observé dans plusieurs systèmes expérimentaux, en particulier lors de la cytocinèse. Nous terminons ce travail par une analyse de la mécanique de formation d'un bleb unique induit par une rupture artificielle du cortex par ablation laser.
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Farooqui, Ausaf Ahmed. "Fronto-parietal cortex in sequential behaviour." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/243944.
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This dissertation investigates the fronto-parietal representation of the structure of organised mental episodes by studying its effect on the representation of cognitive events occurring at various positions within it. The experiments in chapter 2 look at the completion of hierarchically organized mental (task/subtask) episodes. Multiple identical target-detection events were organized into a sequential task episode, and the individual events were connected in a means-to-end relationship. It is shown that events that are conceptualized as completing defined task episodes elicit greater activity compared to identical events lying within the episode; the magnitude of the end of episode activity depended on the hierarchical abstraction of the episode. In chapter 3, the effect of ordinal position of the cognitive events, making up the task episode, on their representation is investigated in the context of a biphasic task episode. The design further manipulated the cognitive load of the two phases independently. This allowed for a direct comparison of the effect of phase vis-à-vis the effect of cognitive load. The results showed that fronto-parietal regions that increased their activity in response to cognitive load, also increased their activity for the later phases of the task episode, even though the cognitive load associated with the later phase was, arguably, lower than the previous phase. Chapter 4 investigates if the characteristics of the higher-level representations, like organization of task descriptions, have a causal role in determining the structure of the ensuing mental episode. Results show this to be true. They also confirm the results of earlier chapters in a different framework. Chapter 5 shows that the effect of episode structure is not limited to the elicited activity, but also affects the information content of the representation of the events composing the episode. Specifically, the information content in many regions of later steps is higher than that of earlier steps. Together, the results show widespread representation of the structure of organised mental episodes.
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Sale, Martin V. "Motor cortex excitability in Parkinson's disease /." Adelaide, 1995. http://web4.library.adelaide.edu.au/theses/09SB/09sbs163.pdf.
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Frey, Stephen. "On the orbitofrontal cortex and encoding." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19464.
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Little is known about the human orbitofrontal cortex and its role in encoding information, although studies in the monkey suggest that it plays an important role in memory. This thesis describes a series of functional neuroimaging studies that investigated the contribution of the orbitofrontal cortex when normal human subjects were engaged in encoding information.
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Schluter, Nathaniel D. "Human premotor cortex : imaging and interference." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284344.
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Mrsic-Flogel, Thomas D. "Development of the ferret auditory cortex." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249548.
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Hardingham, Neil Robert. "Synaptic connections in rat visual cortex." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325298.
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Fotheringhame, David K. "Temporal coding in primary visual cortex." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339357.
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Arthurs, Owen John. "Neurovascular coupling in human somatosensory cortex." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620402.
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Killian, Nathaniel J. "Bioelectrical dynamics of the entorhinal cortex." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52148.
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The entorhinal cortex (EC) in the medial temporal lobe plays a critical role in memory formation and is implicated in several neurological diseases including temporal lobe epilepsy and Alzheimer’s disease. Despite the known importance of this brain region, little is known about the normal bioelectrical activity patterns of the EC in awake, behaving primates. In order to develop effective therapies for diseases affecting the EC, we must first understand its normal properties. To contribute to our understanding of the EC, I monitored the activity of individual neurons and populations of neurons in the EC of rhesus macaque monkeys during free-viewing of photographs using electrophysiological techniques. The results of these experiments help to explain how primates can form memories of, and navigate through, the visual world.
These experiments revealed neurons in the EC that represent visual space with triangular grid receptive fields and other neurons that prefer to fire near image borders. These properties are similar to those previously described in the rodent EC, but here the neuronal responses relate to viewing of remote space as opposed to representing the physical location of the animal. The representation of visual space may be aided by another EC neuron type that was discovered, free-viewing saccade direction cells, neurons that signaled the direction of upcoming saccades. Such a signal could be used by other cells to prepare to fire according to the future gaze location. Many of these spatially-responsive neurons also represented memory for images, suggesting that they may be useful for associating items with their locations.
I also examined the neuronal circuitry of recognition memory for visual stimuli in the EC, and I found that population synchronization within the gamma-band (30-140 Hz) in superficial layers of the EC was modulated by stimulus novelty, while the strength of memory formation modulated gamma-band synchronization in the deep layers and in layer III. Furthermore, the strength of connectivity in the gamma-band between different layers was correlated with the strength of memory formation, with deep to superficial power transfer being correlated with stronger memory formation and superficial to deep transfer correlated with weaker memory formation. These findings support several previous investigations of hippocampal-entorhinal connectivity in the rodent and advance our understanding of the functional circuitry of the medial temporal lobe memory system.
Finally, I explored the design of a device that could be used to investigate properties of brain tissue in vitro, potentially aiding in the development of treatments for disorders of the EC and other brain structures. We designed, fabricated, and validated a novel device for long-term maintenance of thick brain slices and 3-dimensional dissociated cell cultures on a perforated multi-electrode array. To date, most electrical recordings of thick tissue preparations have been performed by manually inserting electrode arrays. This work demonstrates a simple and effective solution to this problem by building a culture perfusion chamber around a planar perforated multi-electrode array. By making use of interstitial perfusion, the device maintained the thickness of tissue constructs and improved cellular survival as demonstrated by increased firing rates of perfused slices and 3-D cultures, compared to unperfused controls. To the best of our knowledge, this is the first thick tissue culture device to combine forced interstitial perfusion for long-term tissue maintenance and an integrated multi-electrode array for electrical recording and stimulation.
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Stensola, Tor. "Population codes in medial entorhinal cortex." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for nevromedisin, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25419.
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Populasjonskoder i mediale entorhinal korteks Hjernebarken utfører kontinuerlig et velde av kompliserte funksjoner, hvis mekanismer vi kan tjene mye på å forstå. Nevrovitenskap er et relativt nytt fag, men med utrolig moment. Mye vites i dag om enkle nevroners egenskaper, men nevral komputering foregår i store trekk i interaksjonene mellom celler. Men på dette planet er det mange hindere som må overkommes; teknologisk nyvinning og konseptuell modning har ført til at nevrovitenskap gjennom de senere år har kunnet tilnærme seg spørsmal som fanger mekanismer på systemnivå. Hippokampus, som inneholder stedsselektive celler, utgjør et eksperimentelt system som tillater spørsmål om visse kjernemekanismer, slik som hukommelsesfunskjon og intern representasjonsdynamikk, uten streng ekpserimentell kontroll på innkommende og utgående signaler slik man baserer seg på i for eksempel sansenevrovitenskap. I hippokampusforskning er dyrets naturlige adferd en enorm ressurs. På grunn av den sterke tilknytningen til rom kan man ved å korrelere nevral aktivitet til dyrets adferd etablere svært robuste forhold mellom nevronenes aktivitet og funksjon på adferdnivå. Dette har ført til at hippokampusforskning har blitt en foregangsfront på innsamling av store datasett i dyr under normal adferd, samt tolkning av denne i adferdskontekst. Et stort skritt mot å forstå hvordan stedsselektiviteten i hippokampus oppstår og brukes kom med funnet av gitterceller, celler som er aktive i et gittermønster som dekker hele miljøet. Vi vet mye om disse cellenes oppførsel på enkeltcellenivå, men på grunn av teknisk krevende innspillingsteknikk har det vært vanskelig å spille inn nok celler til å forstå hvordan disse kombinerer til en populasjonskode for rom. Denne hindringen har vi nå overkommet, og i første arbeid brukte vi nye teknikker for å spille inn store antall gitterceller innen dyr og viser at gittercellekartet er organisert i moduler, hver med sin egen kartgeometri. Vi viser hvordan disse modulene er fordelt i vevet, og utviklet nye analyser for å beskive modulenes egenskaper. Vi viser at gitterkart i forskjellige moduler inad i dyr ikke bare kan innta forskjellig geometriske former, men også utføre separate operasjoner samtidig på samme eksperimentelle manipulering. Dette er første bevis på slik uavhengig funksjon i gitterkartet, og foreslår hvordan stedsceller kan generere høykapasitetslagring av representasjoner for forskjellige miljø. I andre arbeid beskriver vi hvordan en annen funksjonelt definert cellegruppe i entorhinal korteks fungerer på populasjonsnivå, denne gangen for celler som koder retning til dyret i forhold til miljøet. Vi viser at denne populasjonen har en topografisk fordeling langs samme akse i vevet som gitterceller utviser topografi, men at denne er kontinuerlig i motsetning til gitterkartets modulære fordeling. I siste arbeid viser vi at miljøets geometri bestemmer hvordan gitterkartet ankres til det eksterne rom. Vi beskriver en universal ankringsstrategi som er optimal for å skape størst mulig forskjell mellom populasjonskoder for områder langs rommets grenser. Dette brukes kanskje til å forhindre sanseforvirring av gitterkartet i miljø med geometrisk ambiguøse segmenter. Avhandlingen legger frem første beskrivelser av nevrale mekanismer på populasjonsnivå i entorhinal korteks, og gir flere innsikter i generell organisering av nettverkene som er involvert i stedssans og hukommelseCurrent systems neuroscience has unprecedented momentum, in terms of both technological and conceptual development. It is crucial to study systems mechanisms and their associated functions with behavior in mind. Hippocampal and parahippocampal cortices has proved a highly suitable experimental system because the high level functions that are performed here, including episodic memory formation, are accessible through the clear readout of spatial behavior. Grid cells in medial entorhinal cortex (MEC) have been proposed to account for the spatial selectivity in downstream hippocampal place cells. Until now, however, entorhinal grid cells have only been studied on single cell– or small local ensemble level. The main reason for population studies lagging behind that of hippocampus is the technical difficulties associated with entorhinal implantation and recording. Here we have overcome some of the main technical hurdles, and recorded unprecedented number of cells from distinct functional classes in MEC. We show in Paper 1 that the entorhinal grid map is organized into sub-maps–or modules–that contain grid cells sharing numerous features including spatial pattern scale, orientation, deformation and temporal modulation. We also demonstrate that grid modules in the same system can operate independently on the same input, raising the possibility that hippocampal capacity for encoding distinct spatial representations is enabled by the grid input. We further show in Paper 2 that also head direction cells in entorhinal cortex distribute according to a functional topography along the dorsoventral axis. The head direction system, however, was not modular in contrast to the grid system. Finally, Paper 3 details a common grid anchoring strategy shared across animals and environments. The grid pattern displayed a striking tendency to align to the cardinal axes of the environment, but systematically offset 7.5°. Through simulations, we show that this constitutes an optimal orientation of the grid to maximally decorrelate population encoding of environment border segments, providing a possible link to border-selective cells in the mechanisms that embeds internal representation of space into external frames of reference. These findings have implications for our understanding of entorhinal and hippocampal computations and add several new venues for further investigation.
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Rahman, Shbana. "The cerebellar cortex & motor learning." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248049.
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Millar, Laurie. "The cerebellar cortex and motor learning." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415195.
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May, Patrick J. C. "Memory traces in human auditory cortex." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341058.
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Vander, Weele Caitlin Miya. "Dopaminergic modulation of prefrontal cortex subpopulations." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120628.
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Thesis: Ph. D. in Neuroscience, Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2018.Cataloged from PDF version of thesis. Page 176 blank.
Includes bibliographical references (pages 159-175).
Despite abundant evidence that dopamine modulates medial prefrontal cortex (mPFC) activity to mediate diverse behavioral functions, the precise circuit computations remain elusive. One potentially unifying theoretical model by which dopamine can modulate functions from working memory to schizophrenia is that dopamine serves to increase the signal-to-noise ratio in mPFC neurons, where neuronal activity conveying sensory information (signal) are amplified relative to spontaneous firing (noise). To connect theory to biology, we lack direct evidence for dopaminergic modulation of signal-to-noise in neuronal firing patterns in vivo and a mechanistic explanation of how such computations would be transmitted downstream to instruct specific behavioral functions. Here, we demonstrate that dopamine increases signal-to-noise ratio in mPFC neurons projecting to the dorsal periaqueductal gray (dPAG) during the processing of an aversive stimulus. First, using electrochemical approaches, we reveal the precise time course of tail pinch-evoked dopamine release in the mPFC. Second, we show that dopamine signaling in the mPFC biases behavioral responses to punishment-predictive stimuli, rather than reward-predictive cues. Third, in contrast to the well-characterized mPFC-NAc projection, we show that activation of mPFC-dPAG neurons is sufficient to drive place avoidance and defensive behaviors. Fourth, to determine the natural dynamics of individual mPFC neurons, we performed single-cell projection-defined microendoscopic calcium imaging to reveal a robust preferential excitation of mPFC-dPAG, but not mPFC-NAc, neurons to aversive stimuli. Finally, photostimulation of VTA dopamine terminals in the mPFC revealed an increase in signal-to-noise ratio in mPFC-dPAG neuronal activity during the processing of aversive, but not rewarding stimuli. Together, these data unveil the utility of dopamine in the mPFC to effectively filter sensory information in a valence-specific manner.
by Caitlin Miya Vander Weele.
Ph. D. in Neuroscience
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Huang, Ying-Zu. "Theta burst stimulation of human cortex." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445651/.
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It has proved possible in experimental animals to manipulate synaptic efficiency using direct electrical stimulation of central nervous pathways. The introduction of transcranial methods of non-invasively stimulating the human brain raised hopes that similar effects could be produced in humans, with the potential for eventual therapeutic application in disease states. However, largely due to safety limitations, human subjects often require lengthy conditioning with repetitive transcranial magnetic stimulation (rTMS), and even then effects are often weak, variable and not beneficial in the therapeutic setting. In view of the difficulties, I have explored novel methods of conditioning the brain in conscious humans using rTMS which can swiftly produce powerful and controllable long-term changes in the excitability of cortical circuits.
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Hindley, Emma Logan. "The functions of the retrosplenial cortex." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/62777/.
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The functions of the retrosplenial cortex are not clearly understood, and the two current theories of retrosplenial cortex function, the translation and integration theories, are frequently very difficult to distinguish from each other, particularly in the spatial domain. The principal goal of this thesis was to differentiate between the integration and translation theories, and to explore the functions of the retrosplenial cortex in tasks that minimise or remove spatial demands, particularly navigation. The work presented in this thesis demonstrates that the retrosplenial cortex is involved in tasks extending beyond the spatial domain into executive functions and cross--‐modal processing. The retrosplenial cortex has been shown to be required for visually determining location in an environment, in the absence of self--‐generated navigational cues. Further evidence has been presented for the differing roles of the retrosplenial sub--‐regions, which appear to work in conjunction with each other to combine information received from different sensory modalities. However, further work is required to fully understand the ways in which these areas work together and with other areas of the brain, and the implications that dysfunction in this area has for human cognition.
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Beeren, L. K. "Probing network dynamics in barrel cortex." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1348307/.
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Recent studies have demonstrated that a rat can be trained to behaviourally report the electrical stimulation of a single cortical neuron (Houweling and Brecht, 2008). Other studies have reported detection of the optogenetic stimulation of ~300 neurons (Huber et al., 2008). However, although the animal can detect the stimulation, it is unclear what effect this small perturbation is having on the network and to what degree this will alter the animal’s ability to perform a task. This thesis investigates the effect on both the local network and on behaviour of several magnitudes of neuronal perturbation, from a single spike to the excitation of several thousand neurons. Finding the limitations under which a network can function provides powerful insights into how neurons interact to form meaningful networks. I performed simultaneous intra- and multi-unit extracellular recordings from the rat barrel cortex. I introduced a single spike into the patched neuron, and monitored the evolution of network activity via the extracellular probe. I found that the introduction of a single spike in a neuron produces a detectable increase in firing rate in the local network. To extend the investigation, channelrhodopsin-2 (ChR2), a light-sensitive membrane protein, was electroporated under visual control into a small number (1 - 10) of layer 2/3 pyramidal cells in the somatosensory cortex of the adult mouse. After exciting the ChR2-positive neurons, the resulting network activity was measured both by cell-attached and whole-cell patch-clamp recordings from nearby neurons and by monitoring up to 50 nearby cells in different cortical layers using the multi-site silicon probe. I found that excitation of a small number of neurons caused an increase in the spike rate of the local network, which lasted up to 300 ms. On the next level, large-scale perturbations were introduced into the brain by the optogenetic excitation of several thousand neurons in the cortexof transgenic mice expressing ChR2 under the Thy1 promoter. A short (2-20 ms) pulse of blue light produced a strong initial response, measured in both the LFP and spiking activity across supragranular layers of the barrel cortex. This initial response was often followed by ~5 bursts of spikes which resulted in an oscillation in the LFP. This oscillation was found to be of similar frequency and time-scale to an oscillation recorded in the barrel cortex resulting from the deflection of a single whisker. After pharmacologically blocking activity in the thalamus, confirmed by loss of the whisker response, the light-induced oscillations disappeared, indicating that the thalamus is necessary for their propagation. Optogenetic stimulation was also able to generate oscillations in the awake animal. I investigated the effect of such a large perturbation on mice undergoing a simple whisker-deflection discrimination task. It was found that the performance of the mice initially dropped to chance level if a strong perturbation was delivered 100 ms before the sensory stimulation. If the strong perturbation was sustained for every trial, the performance of the mice did not improve. If the perturbing stimulation was removed and then introduced gradually, the animal was able to adapt to the stimulation and learn to perform the task despite the perturbation. In summary, small perturbations have a measurable effect on the local network, implying the use of a rate code for at least some brain states in the barrel cortex. A large perturbation produces a strong cortical response, which often leads to a strong oscillation. The same stimulus interferes with the behaviour of a mouse undergoing a simple task, and yet the mouse can learn to perform accurately despite the noise. Together, these findings suggest a coding regime with high degrees of redundancy and robustness. Although the cortical activity patterns are easily perturbed - even a single spike causes a temporary increase in firing rate - this disturbance does not have debilitating effects on the behaviour or the experience of the animal.
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Benoit, R. G. "Functional specialisation within rostral prefrontal cortex." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/623668/.
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The functional organisation of rostral prefrontal cortex (rPFC; approximating Area 10) is largely unknown. On one hand, this region might support processes that are commonly involved in coping with multiple demands. On the other hand, rPFC might be fractionated into functionally specialised subregions. This thesis examines which of these accounts is more plausible. Therefore, four functional MRI studies were conducted, each of which compared two functions. These were hypothesised to share common processing denominators that might be supported by medial rPFC (mrPFC). It was assessed whether the functions are associated with haemodynamic signal changes in overlapping versus segregated subregions. Study I investigated the involvement of rPFC in prospective memory and in stimulus-oriented (i.e. triggered by the environment) versus stimulus-independent (i.e. decoupled from the environment) processing. Study II asked participants to envision future episodes of spending money (e.g., £35 at a Pub). It was hypothesised that subregions supporting such episodic prospection might also exhibit haemodynamic signal changes as a function of the imagined reward value (e.g., £35). In study III, participants first made personality trait judgements about themselves and others (i.e., their best friends), and then tried to remember the target of each judgement. It was investigated whether mrPFC subregions involved in thinking about oneself during those tasks might also support thinking about others to the degree that the other person is perceived as similar. Study IV examined the relationship between mrPFC engagement during self-appraisal and individual differences in the valuation of future rewards. Overall, the data are most consistent with a synthesis of the two accounts: mrPFC seems to be functionally fractionated. However, the specialised subregions appear to be engaged irrespective of the exact task context (e.g., the nature of the stimuli). Thus, these regions may be characterised as supporting central functions that are involved in coping with multiple demands.
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Pereira, Jacinto José Fonseca. "Computational modeling of prefrontal cortex circuits." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2014. http://hdl.handle.net/10362/12080.
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Dissertation presented to obtain the Ph.D degree in BiologyThe most outstanding feature of the human brain is its ability to perform highly complex cognitive tasks and one key region of the brain involved in these elaborated tasks is the prefrontal cortex. However, little is known about the basic neuronal processes that sustain these capacities. This dissertation describes the computational study of the biophysical properties of neurons in the prefrontal cortex that underlie complex cognitive processes with special emphasis in working memory, the ability to keep information online in the brain for a short period of time while processing incoming external stimuli.(...)
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Vernon, Richard J. W. "Shape processing across lateral occipital cortex." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/16777/.
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There are two predominant means of identifying visual areas in the human brain; retinotopy (exploiting maps of the visual field) and localisers (exploiting functional selectivity). This thesis aimed to bridge those two approaches, assessing the roles of LO-1 and LO-2; two retinotopically-defined regions that show overlap with the functionally-defined (shape selective) Lateral Occipital Complex (LOC). More generally, we asked what is the nature of the shape representation across Lateral Occipital cortex? We first probed the functional roles of LO-1 and LO-2, finding that LO-2 is the more shape-sensitive region of the pair and will respond to second order shape stimuli, whereas LO-1 may process more local cues (perhaps orientation information). Our later work then assessed neural shape representations across visual cortex, identifying two discrete representations; ‘Shape-profile’ (essentially retinotopic responses) and ‘Shape-complexity’ (responses based upon the complexity of a shape’s contour). The latter dimension captured variance in LOC, and surprisingly LO-2. This indicates that even explicit visual field maps can respond to non‑retinotopic attributes such as curvature complexity. Intriguingly, a transition between dimensions occurred around LO-1 and LO-2. Finally, we explicitly tested whether the ‘Shape-complexity’ representation may be curvature based. Our results implied that radial shape protrusions are highly salient features for Lateral Occipital cortex, but it is not necessarily the points of maximal curvature that are being responded to. Instead, we hypothesise that it is the convergent lines comorbid with curvature that neurons may be attuned to, as such lines likely represent the most salient or characteristic features in a given shape. In sum, we argue for an evolving shape representation across visual cortex, with some degree of shape sensitivity first emerging around LO-1 and LO-2. These maps may then be acting as preliminary processing stages for more selective shape tunings in LOC.
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Lieleg, Oliver. "Model systems of the actin cortex." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/672641/672641.pdf.
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Cholfin, Jeremy A. "Genetic regulation of prefrontal cortex development." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3251942.
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Nauhaus, Ian Michael. "Functional connectivity in primary visual cortex." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1692099811&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Peelen, Marius Vincent. "Body selectivity in human visual cortex." Thesis, Bangor University, 2006. https://research.bangor.ac.uk/portal/en/theses/body-selectivity-in-human-visual-cortex(4091f96c-dee2-42ec-9a32-c0a8cf17b288).html.
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Perceiving other people is a seemingly effortless process. Yet within a few hundred milliseconds we are aware of who we are looking at, what this person is doing, and even what this person feels. We derive this information from the form and motion of the face and body. Faces may be particularly important for some aspects of person perception (e. g., identity recognition), whereas bodies may be more important for others (e. g., action recognition). Furthermore, information from the body is important in cases where it is not possible to perceive the details of the face, for instance when the face is occluded, or when we see someone from a distance. In most cases, however, it is likely that information from both the face and the body are perceived in parallel and are integrated at an early stage. Previous research on person perception has mostly focused on the brain mechanisms underlying face perception. Much less research has focused on the brain mechanismsu nderlying body perception,w hich is the topic of this thesis. Using functional magnetic resonance imaging (fMRI) I provide evidence for a previously unknown body-selective visual area that overlaps a face-selective area. By employing novel analysis techniques that take into account patterns of activation across voxels I show that body- and face-selective areas can be functionally dissociated. Finally, I show that, in contrast to frontal and parietal action-recognition areas, visual body-selective areasd o not contain a dynamic representationo f observeda ctions. Together, thesef indings increaseo ur understandingo f the brain mechanismsu nderlying body, face and action perception, by showing both similarities and dissimilarities in the brain structures involved in these processes.
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Volek, Lukáš. "Vývojová deska s ARM Cortex M4." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220344.
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In this work I aimed at designing a universal system for testing either STM32F407/417 by STMicroelectronics and later various sensors and communication buses. The result then is a main board with many specific connectors for individual buses even with connectors making all I/O pins accessible at the same time. Thanks to advanced switching regulators the power supply is capable of accepting a wide range of sources like single Li-Ion cell, pair of alkaline cells, 12V Lead battery, common wall power adapters (both DC and AC up to 15 Vpp ), USB, laboratory power supplies with multiple outputs and finally POE (Power Over Ethernet). Supply voltages are supervised by voltage comparators with an optical signalisation. (It is possible to determine the sick branch without a measuring instrument and blowing components in the most cases.) Another important parameter was a robustness of the supply and communication lines. There is a number of TVSs, chokes, and big and low ESR capacitors A PC software is intended for a basic functionality demonstration only.
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Gloveli, Tengis. "Die funktionelle Bedeutung von Projektionszellen des medialen entorhinalen Cortex in der Interaktion zwischen entorhinalem Cortex und Hippocampus." Doctoral thesis, [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=965714241.
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Cacciamani, Laura, Erica Wager, Mary A. Peterson, and Paige E. Scalf. "Age-Related Changes in Perirhinal Cortex Sensitivity to Configuration and Part Familiarity and Connectivity to Visual Cortex." FRONTIERS MEDIA SA, 2017. http://hdl.handle.net/10150/625802.
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The perirhinal cortex (PRC) is a medial temporal lobe (MTL) structure known to be involved in assessing whether an object is familiar (i.e., meaningful) or novel. Recent evidence shows that the PRC is sensitive to the familiarity of both whole object configurations and their parts, and suggests the PRC may modulate part familiarity responses in V2. Here, using functional magnetic resonance imaging (fMRI), we investigated age-related decline in the PRC's sensitivity to part/configuration familiarity and assessed its functional connectivity to visual cortex in young and older adults. Participants categorized peripherally presented silhouettes as familiar ("real-world") or novel. Part/configuration familiarity was manipulated via three silhouette configurations: Familiar (parts/configurations familiar), Control Novel (parts/configurations novel), and Part-Rearranged Novel (parts familiar, configurations novel). "Real-world" judgments were less accurate than "novel" judgments, although accuracy did not differ between age groups. The fMRI data revealed differential neural activity, however: In young adults, a linear pattern of activation was observed in left hemisphere (LH) PRC, with Familiar > Control Novel > Part-Rearranged Novel. Older adults did not show this pattern, indicating age-related decline in the PRC's sensitivity to part/configuration familiarity. A functional connectivity analysis revealed a significant coupling between the PRC and V2 in the LH in young adults only. Older adults showed a linear pattern of activation in the temporopolar cortex (TPC), but no evidence of TPC-V2 connectivity. This is the first study to demonstrate age-related decline in the PRC's representations of part/configuration familiarity and its covariance with visual cortex.
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Rothé, Marie. "Activités spécifiques du cortex cingulaire antérieur et du cortex préfrontal dorsolatéral et interactions lors de l'adaptation des comportements." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00710536.
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Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l'évaluation de l'action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l'évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d'activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L'étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitation.
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Reyns, Nicolas. "ROLE DU CORTEX MOTEUR DANS LA MODULATION DES AFFERENCES SOMESTHESIQUES. MODELE DE LA STIMULATION ELECTRIQUE DU CORTEX MOTEUR." Phd thesis, Université du Droit et de la Santé - Lille II, 2008. http://tel.archives-ouvertes.fr/tel-00440877.
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La question du rôle du cortex dans la modulation des afférences somesthésiques inhérente à l'intégration sensorimotrice et au contrôle moteur reste l'objet de recherches cliniques et fondamentales. Si le cortex moteur primaire (M1) occupe un rôle central dans le contrôle du mouvement en participant activement à l'élaboration du plan moteur et à son exécution, il semble réciproquement influencé par les afférences somesthésiques générées par le mouvement. Il est probable que réciproquement il soit capable de moduler ces afférences somesthésiques. L'objectif principal de ce travail de thèse était d'apporter des arguments en faveur de cette modulation potentielle des afférences somesthésiques par le cortex moteur. Nous nous sommes, dans ce contexte, intéressés à la stimulation électrique chronique du cortex moteur (SCM) utilisée dans la prise en charge de certaines douleurs neuropathiques et dont les mécanismes de l'effet analgésique demeurent mal connus. Afin de mettre en évidence une possible neuromodulation induite par la SCM nous avons étudié son influence sur les rythmes corticaux liés au mouvement, particulièrement la synchronisation du rythme béta suivant le mouvement (SLE β) sachant qu'il existe des arguments en faveur d'une relation entre SLE β et le traitement cortical des afférences somesthésiques liées au mouvement. La première partie du travail a consisté à conforter cette probable influence des afférences somesthésiques corticales sur la SLE β. Nous avons pour ce faire étudié les profils de SLE β en enregistrement électroencéphalographique (EEG) 128 voies chez des patients présentant, dans un contexte de douleurs neuropathiques, une déafférentation sensitive d'origine centrale ou périphérique, documentée par une altération des potentiels évoqués somesthésiques (PES). Nous avons pu constater que la déafférentation sensitive provoquait une destructuration du profil de SLE β en comparaison à une population de volontaires sains. En effet, les patients présentaient une SLE β dont la distribution spatiale était restreinte et volontiers ipsilatérale au mouvement du côté douloureux contrairement à la distribution spatiale physiologique de la SLE β volontiers bilatérale à prédominance controlatérale au mouvement. Nous avons donc conclu au terme de cette première partie que la SLE β pouvait être considérée comme un reflet des afférences somesthésiques au niveau cortical et un bon outil de l'étude de l'intégration sensori-motrice. La deuxième partie du travail a consisté à étudier les effets de la SCM sur les modifications de la SLE β en condition de déafférentation sensitive. Nous avons exploré les profils de SLE β chez des patients éligibles à une SCM pour la prise en charge de leurs douleurs neuropathiques. Ces explorations ont eu lieu avant et durant la réalisation de la SCM. Nous avons pu constater une modulation significative de la SLE β par la SCM avec une restauration d'une distribution spatiale plus physiologique. Compte tenu du rôle du thalamus dans la génèse des oscillations corticales, des connexions réciproques du cortex moteur et du thalamus et de l'influence des afférences somesthésiques sur la SLE β, nous avons supposé que la SCM facilitait les afférences somesthésiques thalamo-corticales liées au mouvement. Dès lors, nous nous sommes intéressés dans une troisième partie aux effets de la SCM sur les PES de ces patients. Nous avons constaté chez certains d'entre eux une augmentation de l'amplitude des potentiels N20/P25, et ce de façon corrélée à l'effet analgésique de la SCM. Notre travail semble apporter des arguments en faveur d'une capacité du cortex moteur à moduler les afférences somesthésiques tout au moins en condition non physiologique d'une stimulation électrique. Ces résultats sont concordants avec des données cliniques et fondamentales antérieurement rapportées dans la littérature.
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Reyns, Nicolas. "Rôle du cortex moteur dans la modulation des afférences somesthésiques : modèle de la stimulation électrique du cortex moteur." Lille 2, 2008. http://www.theses.fr/2008LIL2S022.
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La question du rôle du cortex dans la modulation des afférences somesthésiques inhérente à l'intégration sensorimotrice et au contrôle moteur reste l'objet de recherches cliniques et fondamentales. Si le cortex moteur primaire (M1) occupe un rôle central dans le contrôle du mouvement en participant activement à l'élaboration du plan moteur et à son exécution, il semble réciproquement influencé par les afférences somesthésiques générées par le mouvement. Il est probable que réciproquement il soit capable de moduler ces afférences somesthésiques. L'objectif principal de ce travail de thèse était d'apporter des arguments en faveur de cette modulation potentielle des afférences somesthésiques par le cortex moteur. Nous nous sommes, dans ce contexte, intéressés à la stimulation électrique chronique du cortex moteur (SCM) utilisée dans la prise en charge de certaines douleurs neuropathiques et dont les mécanismes de l'effet analgésique demeurent mal connus. Afin de mettre en évidence une possible neuromodulation induite par la SCM nous avons étudié son influence sur certains rythmes corticaux liés au mouvement, particulièrement la synchronisation du rythme béta suivant le mouvement (SLE β) dont la corrélation avec le traitement cortical des afférences somesthésiques liées au mouvement semble probable. La première partie du travail a consisté à conforter cette probable influence des afférences somesthésiques corticales sur la SLE β. Nous avons pour ce faire étudié les profiles de SLE β en EEG 128 voies dans une population de patients présentant, dans un contexte de douleurs neuropathiques, une déafférentation sensitive d'origine centrale ou périphérique, documentée par une altération des potentiels évoqués somesthésiques (PES). Nous avons pu constater que la déafférentation sensitive provoquait une destructuration du profile de SLE β en comparaison à une population de volontaires sains. En effet, les patients présentaient une SLE β dont la distribution spatiale était restreinte et volontiers ipsilatérale au mouvement du côté douloureux contrairement à la distribution spatiale physiologique de la SLE β volontiers bilatérale à prédominance controlatérale au mouvement. Nous avons donc conclu au terme de cette première partie que la SLE β pouvait être considérée comme un reflet des afférences somesthésiques au niveau cortical et un bon outils de l'étude de l'intégration sensori-motrice. La deuxième partie du travail à consisté à étudier les effets de la SCM sur les modifications de la SLE β en condition de déafférentation sensitive. Nous avons exploré les profiles de SLE β chez des patients éligibles à une SCM pour la prise en charge de leur douleurs neuropathiques. Ces explorations ont eu lieu avant et durant la réalisation de la SCM. Nous avons pu constater une modulation significative de la SLE β par la SCM sous la forme de la restauration d'une distribution spatiale plus physiologique. Le degré de cette neuromodulation, ainsi que l'amélioration des PES sous la forme d'une augmentation de l'amplitude des potentiels N20/P25, sont apparus corrélés à celui de l'effet analgésique de la SCM. La SCM augmenterait donc au niveau cortical les afférences somesthésiques liées au mouvement. Son effet analgésique pourrait être lié au renforcement de la voie somesthésique non nociceptive dont on connaît l'effet inhibiteur sur la voie spino-thalamique de transmission des informations nociceptives. Notre travail semble apporter des arguments en faveur d'une capacité du cortex moteur à moduler les afférences somesthésiques tout au moins en condition non physiologique de sa stimulation électrique. Ces résultats sont concordants avec des données cliniques et fondamentales antérieurement rapportées dans la littérature
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Rothé, Marie. "Activités spécifiques du cortex cingulaire antérieur et du cortex préfrontal dorsolatéral et interactions lors de l’adaptation des comportements." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10268/document.
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Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l’évaluation de l’action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l’évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d’activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L’étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitationActing optimally in uncertain environments requires evaluating costs and benefits of choosing each alternative. It also requires to flexibly regulate between exploration for and exploitation of resources. One current hypothesis is that the anterior cingulate cortex (ACC), involved in action valuation, and dorsolateral prefrontal cortex (dlPFC), involved in cognitive control, interact to elaborate an optimal regulation of behaviour. Studies achieved during this thesis allowed to precise the role of ACC in the detection and valuation of action outcomes as well as to describe the interactions with dlPFC in a cognitive control loop. Thanks to neurophysiological recordings in behaving monkey our work give new clues on the sequential activation of ACC and dlPFC during adaptation. The analyses of local field potentials allowed us to suggest hypotheses on the underlying oscillatory mechanisms, in particular on low frequency communications between ACC and dlPFC, and their modulation during exploration and exploitation
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Fernandes, Ninette M. "The Detection of Prefrontal Cortex Development into Early Adulthood." Marietta College / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=marietta1164924291.
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Mosley, Alycia. "Chromosomal aneuploidy in the developing mammalian cortex." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3398262.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed May 6, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Mazzetti, Caterina. "A mathematical model of the motor cortex." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/15002/.
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In this work we present a geometric model of motor cortex that generalizes an already existing model of visual cortex.
The thesis opens by recalling the notions of fiber bundles, principal bundles, Lie groups and sub-Riemannian geometry. In particular, we enunciate Chow’s theorem which ensures that if the Hörmander condition holds, the space connectivity property is satisfied.
Then we recall the visual cortex model proposed by Citti-Sarti, which describes the set of simple cells
as a Lie group with sub-Riemannian metric.
The original part of the thesis is the extension
to the motor cortex. Based on neural data, collected by Georgopoulos, we study the set of motor cortical cells and we describe them as a principal bundle. The fiber contains the movement direction and shapes the hypercolumnar structure measured. Finally we determine the intrinsic coordinates of the motor cortex, studying the cellular response to the motor impulse.
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Ehninger, Dan-Achim. "Zelluläre Neogenese im adulten murinen cerebralen Cortex." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970185723.
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Bender, Vanessa Anne. "Cannabinoid-dependent plasticity in rodent somatosensory cortex." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3221443.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed September 18, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Ingvarsson, Thomas, Henrik Lindström, and Christoffer Lind. "Portning till ARM Cortex M3 och prestandajämförelse." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4624.
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The Anybus CompactCom modules are today using the Anybus NP30 processor. These modules are used for communication between industrial machines and larger network protocols. The communication loads on these systems are increasing every day and the limiting factor for the system is the processor.HMS, the company that develops the Anybus CompactCom, has shown interest for a benchmark test between the old processor and a new processor, ARM Cortex-M3. This project includes that benchmark. To be able to get results that reflect reality a test environment was created to simulate Anybus CompactCom conditions. This test environment was achieved by porting HMS operating system to ARM Cortex-M3 and using it combined with a simulated load. The load consists of a number of processes and Ethernet traffic.The results of the benchmark show that the two processors have different strengths. ARM Cortex-M3 is faster at calculating functions while Anybus NP30 has better support for both Ethernet and external memory.
Anybus NP30 är den processor som används i Anybus CompactCom moduler. Modulerna används till kommunikation mellan industrimaskiner och större nätverksprotokoll. Hastighetsstandarden för denna slags kommunikation precis som för all annan kommunikation ökar ständigt och för inbyggda system med tunga nätverksprotokoll är det processorn som begränsar.HMS, företaget som utvecklar Anybus CompactCom, har visat intresse för en prestanda-jämförelse med en ny processor, ARM Cortex-M3. Projektet innefattar denna jämförelse. För att kunna ge en relevant bild av jämförelsen har den gjorts i en testmiljö som ska återspegla den som Anybus CompactCom modulerna arbetar i. Denna testmiljö har uppnåtts genom att HMS operativsystem har portats till ARM Cortex-M3 och använts tillsammans med en last. Lasten består av ett antal processer och Ethernet-trafik.Resultatet av jämförelsen visar att ARM Cortex-M3 och Anybus NP30 har olika styrkor. ARM Cortex-M3 är snabbare på beräkningar, medan fördelar med Anybus NP30 är bättre nätverkshantering och bättre stöd för externt minne.
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Bedwell, S. A. "The connectivity of the mammalian prefrontal cortex." Thesis, Nottingham Trent University, 2015. http://irep.ntu.ac.uk/id/eprint/28042/.
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The fine scale connections of prefrontal cortex (PFC) were investigated in the rat brain, in order to determine organizational properties of PFC pathways which were previously undefined. Neuroanatomical tract tracers (Fluro-Gold, Fluoro-Ruby, Fluoro-Emerald, Biotinylated dextran amines; Fluorescein and Texas red) were injected (20 -100 nl) into subdivisions of PFC (prelimbic, infralimbic, medial-orbital, ventral-orbital, ventrolateral-orbital, lateral-orbital and dorsolateral-orbital) and their projections studied. Tracer studies identified clear evidence of significantly ordered projections from PFC to temporal and sensory-motor cortices in three axes of orientation (p<0.001), showing differential ordering of input and output connections (p<0.001). Ordered connections were consistent across PFC (from anterior to posterior) and showed evidence of changes in organisation in anterior compared to posterior PFC, in both the PFC-temporal and PFC-sensory-motor cortex pathways. Detailed analysis revealed evidence for an organizational gradient in the relationship between inputs and outputs from anterior to posterior PFC, in which retrograde and anterograde labelling become increasingly differentiated as PFC injection site is moved from posterior to anterior. Analysis of fine scale tracer injections (20-30 nl) revealed evidence to show underlying complex organizational properties of connections from PFC to temporal and sensory-motor cortices. Taken together, the findings show that PFC displays ordered arrangements of connections to temporal and sensory-motor cortex, input and output connections are consistently not found in the same locations and the relationship between inputs and outputs differs in relation to the anterior-posterior location in PFC.
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Krug, Kristine. "Ordering geniculate input into primary visual cortex." Thesis, University of Oxford, 1997. https://ora.ox.ac.uk/objects/uuid:b342ffae-4a31-4171-94a6-83cb516e83fe.
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Precise point-to-point connectivity is the basis of ordered maps of the visual field in the brain. One point in the visual field is represented at one locus in the dLGN and one locus in primary visual cortex. A fundamental problem in the development of most sensory systems is the creation of the topographic projections which underlie these maps. Mechanisms ranging from ordered ingrowth of fibres, through chemical guidance of axons to sculpting of the map from an early exuberant input have been proposed. However, we know little about how ordered maps are created beyond the first relay. What we do know is that a topological mismatch requires the exchange of neighbours in the geniculo-cortical projection and that manipulating the input to the primary relay can affect the geniculo-cortical topography. Taking advantage of the immaturity of the newborn hamsterâs visual system, I studied the generation of an ordered map in primary visual cortex during the time of target innervation in normal and manipulated animals. I also investigated the patterning of neuronal activity prior to natural eye-opening. Paired injections of retrograde fluorescent tracers into visual cortex reveal that geniculate fibres are highly disordered at the time of invasion of the cortical plate. Topography in the geniculo-cortical projection emerges out of an unordered projection to area 17 in the first postnatal week. Furthermore, I show that manipulating the peripheral input can alter the topographic map which arises out of the early scatter. Removal of one eye at birth appears to slow the process of geniculo-cortical map formation ipsilateral to the remaining eye and at the end of the second postnatal week, a double projection between thalamus and cortex has formed. If retinal activity is blocked during this time, this double projection does not emerge. The results implicate retinal activity as the signal that induces the development of a different topographic order in the geniculo-cortical projection. It is generally believed that visual experience can influence development only after eye-opening. However, the final part of my thesis shows that neurons in the developing visual cortex of the ferret can not only be visually driven at least 10 days before natural eye-opening, but are also selective for differently oriented gratings presented through the closed eye-lid. Thus, visually-driven neuronal activity could influence development much earlier than previously assumed in many developmental studies.