Made available in DSpace on 2016-03-15T19:40:41Z (GMT). No. of bitstreams: 1 Rita dos Santos de Carvalho Picinini.pdf: 1897105 bytes, checksum: 40db215aab8bca0781df1d15de88b3d3 (MD5) Previous issue date: 2009-01-27 / Fundo Mackenzie de Pesquisa / Different mathematical skills have been investigated over time and, with the advance of neuroimaging techniques, such as PET (Positron Emission Tomography) and fMRI (functional Magnetic Resonance), central components of arithmetical processing have been identified in the parietal and the pre-frontal cortices. Besides the advances of the neuroimaging techniques, other techniques such as non-invasive brain modulation have also been studied such as the transcranial magnetic stimulation (TMS) and the transcranial direct current stimulation (TDCS) in the involvement of cognitive functions in the area of calculation. This study aimed at investigating the impact of anodal TDCS applied over the left dorsolateral pre-frontal cortex (LDLPFC), right parietal cortex (RPC), left parietal cortex (LPC) while the subject was performing multiplication operations. Fifteen healthy volunteers, students of psychology, aged between 18 and 30 years old, have held subtests of the WAIS III and the multiplication task. The results showed that the anodal TDCS over the RPC improved the performance of men regarding the number of rightness. The influence of TDCS on volunteers who had worse performance took place not on complex tasks, but simple arithmetical ones. Besides, the influence of TDCS on volunteers who had better performance was in complex tasks, not simple ones. These results show that the effects of the TDCS on a certain function depend on the baseline values of each volunteer. The other stimulation conditions over the LDLPFC and LPC did not show any significant results. The TDCS can bring a beneficial effect in calculation tasks, depending on the intensity, polarity, time and location of stimulation, resulting in the increased or diminished cortex excitability. / Diferentes habilidades matemáticas vêm sendo investigadas ao longo dos tempos e, com o avanço das técnicas de neuroimagem, como PET (Tomografia por emissão de Pósitrons) e fMRI (ressonância magnética funcional) componentes centrais no processamento aritmético vêm sendo identificados em córtex parietal e pré-frontal. Além do avanço das técnicas de neuroimagem, outras técnicas como de modulação cerebral não-invasiva também vêm sendo estudadas, como Estimulação Magnética Transcraniana (EMT) e a Estimulação Transcraniana por Corrente Contínua (ETCC) no envolvimento das funções cognitivas com a área de cálculo. Este estudo teve como objetivo investigar o impacto da ETCC anódica quando aplicada no Córtex Pré-Frontal Dorsolateral (CPFDLE), Córtex Parietal Direito (CPD), Córtex Parietal Esquerdo (CPE) no desempenho em operações de multiplicação. Quinze voluntários saudáveis, estudantes de psicologia, com faixa etária entre 18 e 30 anos, realizaram subtestes do WAIS III e a tarefa de multiplicação. Os resultados desse estudo mostraram que a ETCC anódica aplicada no CPD melhorou o desempenho dos homens em relação ao número de acertos. A influência da ETCC em participantes com pior desempenho em Aritmética se deu em tarefa simples de multiplicação, mas não complexa, ao passo que a influência da ETCC em participantes com melhor desempenho em Aritmética se deu em tarefa complexa de multiplicação, mas não em simples. Tais resultados sinalizam que os efeitos da estimulação em uma determinada função dependem dos valores de linha de base de cada participante As outras condições de estimulações, CPFDLE e CPE não resultaram em efeitos significativos. A ETCC pode produzir um efeito benéfico em tarefas de cálculo, dependendo da intensidade, polaridade, tempo e localização da estimulação, podendo resultar em aumento ou diminuição na excitabilidade do córtex.

L'adaptation motrice permet d'ajuster la sortie motrice en réponse à des perturbations de l'environnement. Au début de l'adaptation, un processus stratégique conscient appelé recalibration a lieu. Ce processus implique le cervelet et le cortex pariétal postérieur. Il permet de réduire les erreurs motrices en se basant sur le retour sensoriel. Les patients dystoniques ont des altérations du traitement de l'information somatosensorielle. Nous avons fait l'hypothèse que cela devait entrainer des anomalies d'adaptation au cours de la phase de recalibration. En utilisant l'imagerie par résonnance magnétique (IRMf) et la magnétoencéphalographie (MEG), nous avons enregistré l'activité cérébrale chez des patients ayant une crampe de l'écrivain et chez des volontaires sains, alors qu'ils réalisaient une tâche de pointage avec ou sans perturbation visuelle associée. L'étude en IRMf a révélé l'implication d'un réseau cérébello-pariétal postérieur dans la détection des erreurs motrices. Ce réseau était hypoactif chez les patients qui compensaient en recrutant un réseau alternatif plus cognitif mettant en jeu la mémoire visuo-spatiale et la représentation cognitive de la main. La MEG nous a permis d'analyser la dynamique temporelle des activations et de montrer en particulier que la préparation du mouvement est déjà anormale chez les patients; de réaliser une analyse fréquentielle de la communication cérébello-corticale. Cette analyse a révélé un défaut de cohérence dans la bande gamma, entre le cervelet et le cortex moteur et prémoteur ainsi qu'avec le cortex pariétal postérieur. L'ensemble de nos résultats suggère un désordre constitutionnel de ce réseau dans la dystonie. / Dystonia is a movement disorder characterized by prolonged muscle contractions causing involuntary repetitive twisting movements and abnormal postures. Motor adaptation shapes the motor output according to the changes in the environment. At its early stage, motor adaptation involves a strategic conscious process called “recalibration” that minimizes the perturbation and reduces the motor error based on online integration of sensory feedback. Sensorimotor processing is impaired in dystonia and we hypothesized that this may lead to deficits of the “recalibration” phase during motor adaptation. We used magnetoencephalography (MEG) and functional magnetic resonance imagery (fMRI) to record brain activation in patients with writer’s cramp and healthy volunteers using a classical rotation learning task. The fMRI study revealed that the cerebello-parietal network was directly implicated in motor error detection. In writer’s cramp, this network was underactivacted and patients relied more on cognitive networks based on visuospatial memory and cognitive representations of the hand. With MEG, (1) we reconstructed the temporal dynamic of activations in the cerebello-parietal network and demonstrated abnormal movement preparation in writer’s cramp patients; (2) we realized a spectral analysis of the cerebello-parietal communication. This analysis revealed decreased gamma coherence between the cerebellum, and the premotor and motor cortices and with posterior parietal cortex. All of our data suggest an underlying disorder of this network in dystonia.

Les aires cérébrales frontales et pariétales sont impliquées dans différents processus cognitifs importants pour la performance visuelle, tels que l'attention ou la conscience. Malgré les preuves existantes en faveur d'une implication de ces régions dans la cognition visuelle, leurs contributions dans le traitement de stimuli non masqués de faible contraste ainsi que l'activité spatio-temporelle sous-tendant ces contributions restent largement inexplorées, tout particulièrement en termes de causalité. Nous avons mené une exploration approfondie de ces contributions chez l'humain, en mettant l'accent sur la dynamique de l'activité neurale et les améliorations perceptives potentielles qui peuvent résulter de la manipulation non invasive de l'activité cérébrale. À cette fin, nous avons testé chez des sujets sains les effets d'impulsions simples ou de rafales courtes de stimulation magnétique transcrânienne (SMT) réelle versus fausse, délivrée sur le champ oculomoteur frontal ou le sillon intrapariétal avant la présentation d'un filtre de Gabor de faible contraste, sur la discrimination et la détection consciente de ce filtre de Gabor. Nos résultats montrent que chez l'humain, la distribution spatio-temporelle de l'activité frontale et pariétale joue un rôle causal dans la performance visuelle. Nos recherches contribuent à mieux comprendre les bases oscillatoires de la cognition visuelle et les comportements associés et à préparer le terrain pour le développement de nouvelles thérapies basées sur la manipulation non-invasive de l'activité cérébrale oscillatoire avec, pour objectif ultime, l'amélioration des pathologies neuropsychiatriques. / Frontal and parietal areas have been shown to subtend different cognitive processes such as attentional orienting, decision making and access to consciousness, with bearing on visual performance. In spite of prior evidence supporting an implication of those regions in visual cognition, their contributions to the processing of low-contrast unmasked stimuli and the characteristic spatiotemporal activity patterns underlying them remain to be fully explored and causation is lacking. We here addressed a thorough exploration of such contributions in humans, with an emphasis on the dynamics of neural activity and visual performance enhancements as probed by patterns of noninvasive manipulation of local brain oscillatory activity. To this end, we tested in healthy participants the effects of either single pulses or short bursts of active vs. sham transcranial magnetic stimulation (TMS), delivered to the frontal eye field (FEF) and the intraparietal sulcus (IPS) prior to the presentation of a lateralized low-contrast near-threshold Gabor stimulus, on the visual discrimination and conscious detection of such stimulus. Our findings contribute to better substantiate the oscillatory basis of visual cognition and its associated behaviors and to set the stage for the development of novel therapies based on noninvasive manipulation of dysfunctional brain oscillatory activity.

L’étude de l’art pariétal paléolithique a pris un nouveau tournant ces dernières décennies, depuis que la communauté scientifique se trouve confrontée au développement d’algues, de bactéries et de champignons qui menacent certaines représentations parmi les plus fameuses au monde. Les péripéties que connaît la grotte de Lascaux (Montignac-sur-Vézère, Dordogne), depuis sa découverte en 1940 et la fermeture au public en 1963, ont fait prendre conscience de l’extrême fragilité du milieu souterrain, dont l’équilibre peut être rompu par de simples variations des conditions climatiques et environnementales. Certes, les formes biologiques n’ont de cesse de fasciner les hommes, leurs liens implicites avec l’art est manifeste depuis la Préhistoire et se retrouve aujourd’hui dans l’art contemporain ou l’architecture. Mais la compréhension de l’influence des microorganismes (à l’origine de processus d’altérations) sur la facture des œuvres ou leur évolution dans le temps, rend tangible la nécessité de considérer la grotte ornée comme un écosystème dont l’interface entre la paroi et l’atmosphère doit être examinée sous l’angle de la physique-chimie et de la microbiologie. Parmi les formes d’altérations biologiques décrites en grotte, le mondmilch est très largement répandu, mais la part des bactéries dans la mise en place et l’organisation structurale de ce type de concrétion pariétale reste méconnue. Dans une perspective diachronique, le mondmilch mérite d’être mis en relation avec l’art préhistorique : à la fois support et altéragène potentiel des représentations, ses implications vont au-delà de l’aspect esthétique. Datation de l’art pariétal, rôle dans la conception de cet art par les hommes du Paléolithique ou indicateur de la santé d’une grotte sont autant de facettes abordées dans ce travail qui a pour ligne directrice l’intégration et la prévention du risque de voir peu à peu disparaître certains joyaux du patrimoine mondial. / The study of Paleolithic parietal art took a new turn during the last decades, since the scientific community has been confronted with the development of algae, bacteria and fungi that jeopardize some representations among the most famous around the world. The episodes that have been taking place in Lascaux cave (Montignac-sur-Vézère, Dordogne), since its discovery in 1940 and its closure to the public in 1963, made people conscious of the extreme fragility of cave environment, whose equilibrium can be broken by simple variations of environmental and climatic conditions. Biological forms certainly still fascinate people; their implicit links with art is evident since the Prehistoric times and can be found in contemporary art or architecture nowadays. A better understanding of the microorganisms influence (they are the cause of alteration processes) on the state of the paintings, drawings or engravings, or on their evolution in time, makes us understand that it is necessary to consider a painted cave as an ecosystem whose interface between the wall and the atmosphere has to be examined from the points of view of physics, chemistry and microbiology. Among the forms of biological alterations described in the caves, moonmilk is highly common, but the role of bacteria in the setting up and the structural organization of this kind of wall concretion is still little-known. In a diachronic perspective, moonmilk deserves to be put in relation with prehistoric art: at the same time support and potential factor of alteration of the representations, its implications go beyond the esthetical aspect. The dating of parietal art, its role in this art conception by people from the Paleolithic or its function as indicator of a cave health are some of the aspects studied in this work, whose guidelines are the integration and the prevention of the risk of seeing some masterpieces of world heritage disappear little by little.

This study investigated the effects of repeated administrations of nicotine (0.7 mg/kg) on dendritic morphology in the nucleus accumbens (NAcc), prefrontal cortex (Cg 3), and parietal cortex (Par 1). Animals were habituated for 3 days to a locomotor box, and after habituation, every second day for 5 weeks rats were placed into the locomotor chamber immediately after a subcutaneous injection of nicotine or saline. Rats demonstrated tolerance to an initial hypoactive response after each nicotine injection, and this was followed by an increase in activity after each injection (behavioral sensitization). This increase in activity was still present on a nicotine challenge after a 2-week abstinence period. One week after the nicotine challenge day, all rats were perfused and brains were removed. These brains we stained using Golgi-Cox procedures, and dendrites from the nucleus accumbens (N Acc), medial frontal cortex (Cg 3) and parietal cortex (Par 1) were analyzed using the camera lucida procedure. Results showed that rats receiving nicotine demonstrated an increase in dendritic length and spine density relative to controls in the NAcc and Cg3 brain areas, but not Par 1. The increase observed in the NAcc was significantly greater than what has been found with amphetamine or cocaine, and possible underlying mechanisms were discussed.

Path integration is a navigational process that humans and animals use to track changes in their position and orientation. Animal and computational studies suggest that a spatially-tuned navigation system supports path integration, yet this system is not well understood in humans. Here, the prediction was tested that path integration mechanisms and goal-directed navigation in humans would recruit the same key brain regions within the parietal cortex and medial temporal lobes as predicted by animal and computational models. The three experiments described in this dissertation used behavioral and functional magnetic resonance imaging methods in 131 adults (18-35 years) to examine behavioral and brain correlates of navigation. In a landmark-free environment, path integration mechanisms are utilized to update position and orientation to a goal. Experiment 1 examined neural correlates of these mechanisms in the human brain. The results demonstrated that successful first and third person perspective navigation recruited the anterior hippocampus. The posterior hippocampus was found to track distance and temporal proximity to a goal location. The retrosplenial and posterior parietal cortices were additionally recruited for successful goal-directed navigation. In a landmark-rich environment, humans utilize route-based strategies to triangulate between their position, landmarks, and navigational goal. Experiment 2 contrasted path integration and landmark-based strategies by adding a solitary landmark to a sparse environment. The results demonstrated that successful navigation with and without an orienting landmark recruited the anterior hippocampus. Activity in the bilateral posterior hippocampus was modulated by larger triangulation between current position, landmark, and goal location during first person perspective navigation. The caudate nucleus was additionally recruited for landmark-based navigation. Experiment 3 used functional connectivity methods coupled with two fMRI tasks to determine whether areas responsive to optic flow, specifically V3A, V6, and the human motion complex (hMT+), are functionally connected to brain regions recruited during first person perspective navigation. The results demonstrated a functional relationship between optic flow areas and navigationally responsive regions, including the hippocampus, retrosplenial, posterior parietal, and medial prefrontal cortices. These studies demonstrate that goal-directed navigation is reliant upon a navigational system supported by hippocampal position computations and orientation calculations from the retrosplenial and posterior parietal cortices.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第12817号 / 論医博第2079号 / 新制||医||1004(附属図書館) / 31304 / 京都大学大学院医学研究科脳統御医科学系専攻 / (主査)教授 河野 憲二, 教授 金子 武嗣, 教授 大森 治紀 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

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