Le prélèvement crânien monocortical pourrait affaiblir la zone prélevée et exposer à des complications. Nous avons conçu un mouton pendule de Charpy validé sur 12 têtes de cadavres humains. L’énergie du choc était augmentée jusqu’à fracture de la zone pariétale. Pour mesurer l’épaisseur avec un système de navigation optoélectronique, nous avons comparé cinq méthodes non destructives.Dans la deuxième partie, la quantification de la perte de résistance était réalisée sur 30 têtes humaines en comparant le choc maximal supportable avant fracture du côté prélevé avec le côté non prélevé.La troisième partie de l’étude a été menée sur 34 têtes de cadavres de brebis. La perte de résistance de la zone prélevée était de 36% (p=1.10-10) avec une diminution d’épaisseur de 40%. La corrélation entre les deux paramètres était modérée (R=0.46) mais significative (p<0,0001). Chez la brebis, la diminution de résistance du côté prélevé était de 49% (p=6.10-10).Ces données nous permettrons de réaliser une étude animale, pour évaluer la résistance de la zone prélevée reconstruite par un ciment d’hydroxyapatite. / The monocortical parietal bone graft could decrease the strength of the donor site. Complication could occur. We performed a Charpy impact machine and validated it on 12 human cadaver heads. The chock energy was increased until the fracture of the target zone. The thickness measurement was performed with an optoelectronic navigation device. We compared 5 non destructive methods. In the second part, the quantification of the resistance loss was performed on 30 human cadaver heads. The maximum impact resistance of bone on the donor side was compared with the intact side. The third part of the study was performed on 34 sheep cadaver heads. Loss of strength at the donor site was 36% (p=1.10-10) for 40% loss of thickness. Although correlation between these two parameters was rather moderate (R=0.46), it was highly significant (p<0.0001). On sheep, the loss of strength at the donor site was 49% (p=6.10-10).Bone removal results in a highly loss of strength on human and sheep. These data will permit to perform an animal study to evaluate the resistance of the harvest cranial zone rebuilt with hydroxyapatite cement.

Depressive disorders impose a significant mental health burden on individuals and our society. Among smokers there is a high comorbidity of depression/depressive symptoms (e.g., Glassman et al., 1998). Here the parietal EEG alpha asymmetry was used as a dimensional neuropsychological marker of depressive symptoms (i.e., the more depressed, the higher alpha power in the right vs. left parietal lobe during visuospatial tasks [Henriques & Davidson, 1997; Rabe et al, 2005]). Participants, all of whom were smokers and none of whom were clinically depressed, were randomly assigned to the Bupropion group (n = 30) or Placebo group (n = 80) in this double blind study. EEG data during the performance of a visuospatial task were collected prior to and after 14 days on bupropion or placebo capsules. It was found that bupropion significantly reduced the right parietal alpha power and parietal asymmetry whereas placebo did not. Self-reports on depressive symptoms with the Beck Depression Inventory (BDI) were also collected but they did not change after bupropion treatment, suggesting that EEG measures are more sensitive to subtle/early bupropion’s antidepressant effects. Finally the close investigation of individual differences showed that positive (vs. negative) parietal asymmetry during pretreatment predicted greater benefits from bupropion treatment. The present study sheds light on the antidepressant mechanisms of bupropion and represents a valuable addition to the paucity of research on the effects of bupropion on brain activity with EEG measures in general.

abstract: Understanding where our bodies are in space is imperative for motor control, particularly for actions such as goal-directed reaching. Multisensory integration is crucial for reducing uncertainty in arm position estimates. This dissertation examines time and frequency-domain correlates of visual-proprioceptive integration during an arm-position maintenance task. Neural recordings were obtained from two different cortical areas as non-human primates performed a center-out reaching task in a virtual reality environment. Following a reach, animals maintained the end-point position of their arm under unimodal (proprioception only) and bimodal (proprioception and vision) conditions. In both areas, time domain and multi-taper spectral analysis methods were used to quantify changes in the spiking, local field potential (LFP), and spike-field coherence during arm-position maintenance. In both areas, individual neurons were classified based on the spectrum of their spiking patterns. A large proportion of cells in the SPL that exhibited sensory condition-specific oscillatory spiking in the beta (13-30Hz) frequency band. Cells in the IPL typically had a more diverse mix of oscillatory and refractory spiking patterns during the task in response to changing sensory condition. Contrary to the assumptions made in many modelling studies, none of the cells exhibited Poisson-spiking statistics in SPL or IPL. Evoked LFPs in both areas exhibited greater effects of target location than visual condition, though the evoked responses in the preferred reach direction were generally suppressed in the bimodal condition relative to the unimodal condition. Significant effects of target location on evoked responses were observed during the movement period of the task well. In the frequency domain, LFP power in both cortical areas was enhanced in the beta band during the position estimation epoch of the task, indicating that LFP beta oscillations may be important for maintaining the ongoing state. This was particularly evident at the population level, with clear increase in alpha and beta power. Differences in spectral power between conditions also became apparent at the population level, with power during bimodal trials being suppressed relative to unimodal. The spike-field coherence showed confounding results in both the SPL and IPL, with no clear correlation between incidence of beta oscillations and significant beta coherence. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2017

The purpose of this project was to compare the Attention to Memory (AtoM) and the Episodic Buffer (EB) Models. The AtoM model proposes that the ventral parietal cortex (VPC) and dorsal parietal cortex (DPC) are responsive to bottom-up and top- down attention to memory, respectively, (Cabeza, 2008; Cabeza et al., 2008; Ciaramelli et al., 2008). The EB model, on the other hand, proposes that the VPC is involved in the episodic buffer component of Baddeley's working memory model (Vilberg & Rugg, 2008). Using objective (source) and subjective (Remember/Know) retrieval tasks, specific patterns of PPC activity were posited based on the propositions of the AtoM model. These expectations included greater VPC activity for Remember and False Alarms compared to Correct Rejections and Subjective Know, greater DPC activity for Know and Objective Remember compared to Subjective Remember and correct rejections, and no difference in VPC activity for remembering both font and color compared to remembering only one contextual detail. During encoding participants saw words in one of two colors, red or yellow, and in one of two fonts, curvy or straight, and were required to indicate the color the word was presented in. Following each encoding scan participants performed either an Objective or Subjective retrieval task. During Objective retrieval task, participants performed a forced-choice source memory test choosing the word with the correct fontand color or the "new" option. During Subjective retrieval participants were presented with the word in a neutral font and white color and performed a Remember/Know test. On the Subjective retrieval task both VPC and DPC were active for recollection compared to familiar items and Correct Rejections. On the Objective retrieval task the DPC was active for all correct old responses. Neither the VPC nor the DPC were significantly active for False Alarms on both the Subjective and Objective tasks. Both VPC and DPC were more active for Subjective Remember compared to Objective Remember response. Neither PPC region was more active for remembering font and color compared to remembering only font or color. Memory load effects for retrieval of information from long-term memory were only seen in the hippocampus on the Subjective retrieval task. These patterns of activity support the role of the VPC in recollection, as seen on the Subjective task, and the role of the DPC in familiarity, as shown in both the Subjective and Objective tasks. The role of the VPC and DPC during recollection and familiarity processing supports both the AtoM and the EB model. The key predictor of the Episodic Buffer model, memory load effects, was not supported and provides the only evidence against one of the two proposed models. Future work should examine the role of the posterior parietal cortex in spontaneous episodic retrieval to assess the validity of the AtoM model. Advanced imaging analysis techniques should be used to determine functional connectivity between the PPC and frontal and temporal memory regions.

Research on numerical cognition proposes that there are two systems for the perception of numerical quantity, a small-number system (1~3) invoking parallel individuation, or “subitizing”, and a large-number system (4+) that is based on Weberian magnitude estimation (Hyde, 2011). Many numerical cognitive neuroscientists have focused on studying how the magnitude of numerosities (small vs. large numbers) and numerical distance (close vs. far differences between numbers) are influential factors when processing numbers and change detection. However, is there a difference when numerosities are increasing or decreasing? The effects of direction on numerical change processing are lesser known. This 128-channel EEG study investigated the neurobehavioral basis of differentiation between small vs. large-number perception and effects of change directionality. During EEG data collection, participants were sequentially presented with stimulus arrays of 1 to 6 dots, with parameters like size and location controlled for, to minimize varying non-numerical visual cues during habituation. Participants were instructed to press a key whenever they detect a change in the number of dots presented. The current study adapts a dot-stimuli numerical change study design from Hyde and Spelke (2009, 2012). In their EEG study, the researchers examined event-related-potential (ERP) differences during the processing of small (1, 2, 3) and large (8, 16, 24) numbers. For this study, we chose to examine a narrower numerical range from 1~6, so that small (1, 2, 3) vs. large (4, 5, 6) contrasts were along a numerical continuum. In contrast to Hyde and Spelke (2009, 2012), where participants passively-viewed the sequential presentation of dot arrays, this study employed an active change detection paradigm, where participants’ reaction time (RT) and accuracy in detecting change in the number of dots were recorded. We investigated the effects of Direction and Size in numerical change detection, where Direction is operationally defined as Decreasing and Increasing change in numeric set size, while Size is divided into Small-to-Small, Large-to-Large and Crossovers. Numerical change conditions were categorized into six groups: “Increasing Small-to-Small” (e.g., 1-to-2, 2-to-3), “Decreasing Small-to-Small” (e.g., 2-to-1, 3-to-2), “Increasing Large-Large” (e.g., 4-to-6, 5-to-6), “Decreasing Large-Large” (e.g., 5-to-4, 6-to-5), Increasing Small-to-Large” (e.g., 2-to-4, 3-to-5, 3-to-6) and “Decreasing Large-to-Small” (e.g., 4-to-2, 5-to-2, 6-to-3), where the last two groups are operationally defined as Crossovers. There was also a “No Change” condition, where the number of dots remain the same for up to five presentations. ERP analyses were conducted for the N1 component (125-200 ms) over the left and right occipital-temporal-parietal (POT) junction and for the P3b component (435-535 ms) over the midline parietal area (Pz). During the No Change condition, results show that the N1 amplitude was modulated by the cardinal values of the habituated numbers 1~6. Within this continuous range, we found N1 amplitudes commensurate with cardinal values in the small range (1, 2, 3), but not in the large range (4, 5, 6), suggesting that numbers in the subitizing range are individuated as objects in working memory. Meanwhile, in the Change condition, there was a significant main effect of Direction on N1 peak latency, where the Increasing condition showed earlier peaks. In the Decreasing Small-to-Small condition, N1 amplitudes were the lowest (even lower than N1 peaks for No Change conditions), while the other five Change conditions all produced higher N1 negativities than No Change conditions. These results imply that when the number of dots get small enough to parallel individuate, instead of encoding items into visual short-term memory, the brain is “off-loading” items from our perceptual load. Intriguingly, although the Decreasing Small-to-Small condition had the lowest N1 negativities, it produced the highest P3b positivity. Distinctions in P3b waveforms reflect a clear categorical break between small vs. large numbers, where easier/small number change conditions have higher amplitudes than harder, large number conditions, suggesting more difficulty with updating the context in the latter. However, in contrast to the earlier N1, there was no main effect of Direction on P3b peak latency, but there was an interaction effect of Direction by Size. Interestingly, there was also a similar interaction effect of Direction by Size for reaction times, with similar trends showing that Decreasing conditions produced shorter reaction times for the Large-to-Large and Crossover conditions, yet this pattern was reversed in the Small-to-Small condition. This lends more support to the implication of the “off-loading” phenomenon when processing decreases of numerosities in the small range (1~3). Meanwhile, when it comes to context-updating at later stages, and a behavioral response is required for this change detection task, the Large-to-Large condition prove to be the most difficult, as there was lower accuracy, longer reaction times, later and lower P3b peaks. N1 and P3b amplitudes are complementary to each other, with the early N1 being more sensitive to Direction, and the later P3b being more sensitive to Size. This suggests that the posterior parietal cortex might encode Direction first, followed by Size. This study proposes a model that is an adaptation to the P3b context-updating model (Donchin, 1981), where the early, sensory N1 interplays with the later, cognitive P3b. These findings suggest a neurobehavioral basis for the differentiation of small vs. large number perception at early stages of processing that is sensitive to encoding vs. off-loading objects from perceptual load and visual short-term memory, as well as a later stage that involve higher-order cognitive processing on the magnitude of set size that is employed in numerical change detection tasks.

No description available.

La neuromodulation apporte une extraordinaire richesse à la dynamique des réseaux de neurones. Parmi les neuromodulateurs du système nerveux central, la noradrénaline permettrait de faciliter l'adaptation du comportement face aux variations des contraintes environnementales en modulant l'attention, cette fonction au coeur de la cognition qui nous permet de sélectionner l'information la plus pertinente en fonction de notre but. Ce processus complexe qui opère à chaque instant à la fois dans l'espace et le temps, constitue une étape essentielle dans cette adaptation comportementale. Cependant, à ce jour, les mécanismes par lesquels ce neuromodulateur exerce ses effets sur le cerveau sain demeurent mal connus. Mon travail de thèse a pour objectif d'examiner les déterminants comportementaux et les marqueurs neuronaux de l'effet stimulant des agonistes noradrénergiques. La question posée était : "Comment la noradrénaline agit-elle pour optimiser l'attention?" Pour répondre à cette question, j'ai choisi de combiner la pharmacologie, l'analyse du comportement, et l'imagerie par résonnance magnétique fonctionnelle chez le singe. Un des principaux résultats de mes travaux est que l'administration d'agents noradrénergiques induit une large réorganisation des réseaux cérébraux, qui pourrait être à l'origine de l'optimisation des réponses comportementales observées parallèlement / Neuromodulation provides an extraordinary wealth to the dynamics of neural networks. Among the neuromodulators of the central nervous system, noradrenaline would facilitate behavioral adaptation facing variations of environmental constraints by modulating attention, this function at the heart of cognition that allows us to select the most relevant information based our goal. This complex process that operates at every moment both in space and time, is an essential step in this behavioral adaptation. However, to date, the mechanisms by which this neuromodulator exerts its effects on healthy brain remain unknown. My thesis aims to examine the behavioral and neural markers of the boosting effect of noradrenergic agonists. The question asked was: "How does noradrenaline optimize attention?" To answer this question, I chose to combine pharmacology, behavior analysis, and functional Magnetic Resonance Imaging in monkeys. One of the main results of my work is that the administration of noradrenergic agents induced a large-scale brain networks reorganization, which could be responsible for optimizing behavioral responses observed in parallel

Made available in DSpace on 2016-08-15T20:31:06Z (GMT). No. of bitstreams: 1 AndreMV_DISSERT.pdf: 26149415 bytes, checksum: 8052cd9f22e05a0bada5a1c6b968c995 (MD5) Previous issue date: 2011-10-12 / The inversion period of the yolk sac as the dynamic which results from this process was studied in 30 female of prea on days 6, 10, 11 to 15, 20, 25, and 30 of gestation. Six groups of animals (one male for five females) were formed and kept in boxes of 5m2. Vaginal cytology was performed daily for detection of copulation. Pregnant females were separated of the other individuals of the group. They were euthanized using a specific anesthetic protocol for collection of the gestational sacs. Then, the material was processed for histology, immunohistochemistry, scanning electron microscopy, and transmission electron microscopy. At days 11 to 13 of gestation was observed the development of the parietal and visceral endoderm delimiting the yolk sac cavity. The parietal endoderm was coating the surface of the fetal side of the chorioallantoic placenta and surrounding the space bounded by the capsular decidua. These endoderm layers showed a prismatic shape and were separated of the trophoblast by a developed Reichert s membrane. The visceral endoderm contained vitelline vessels and villi in some areas. On the 13th day it was possible to establish as a basic condition before the inversion of teh yolk sac, the permanence of at least one of the three elements that characterized the bilaminar omphalopleure. On the 14th day of gestation the complete inversion of the yolk sac, which was characterized by the degeneration of both parietal endoderm and mural trophoblast, coupled with the gradual disappearance of the Reichert s membrane was observed. As a consequence of this, the visceral endoderm constitutes the interface with the uterine epithelium. After the inversion of the yolk sac, the parietal endoderm remained intact was the one which rested on the surface of the chorioallantoic placenta, which showed high columnar cells, characteristic of the pseudostratified epithelium. The visceral endoderm showed numerous apical villi mainly in regions close to the chorioallantoic placenta. The intense vascularization was confirmed by the immunohistochemistry reaction for vimentin associated with the scanning electron microscopy. During the continuous development of the embryo and chorioallantoic placenta it was also observed the development of an important area of apposition of both visceral and parietal endoderm whose proliferative capacity of these cells was demonstrated by immunohistochemistry using PCNA antibody. Therefore, we concluded the inversion of the yolk sac represents an anatomical arrangement in favor of embryonic development as well as an evolutionary characteristic in this rodent specie. / O período de inversão do saco vitelino bem como a dinâmica resultante deste processo foi estudado em 30 fêmeas de preás nos dias 6, 10, 11 a 15, 20, 25 e 30 de gestação. Foram formados seis grupos de animais numa relação de um macho para cinco fêmeas, mantidos em boxes de 5m2. Após formação dos grupos, diariamente eram realizados exames de citologia vaginal, para verificação de cópula, separando-se dos grupos as fêmeas que eram cobertas. A partir da ocorrência da cópula programaram-se as coletas dos sacos gestacionais mediante sacrifício das fêmeas gestantes através de protocolo anestésico específico. O material, então, era processado segundo técnicas para histologia convencional, imunohistoquímica, microscopia eletrônica de varredura e de transmissão. Nos dias de 11 a 13 de gestação observou-se o desenvolvimento dos endodermas parietal e visceral delimitando a cavidade do saco vitelino. O endoderma parietal foi evidenciado revestindo a superfície fetal da placenta corioalantoide bem como contornando o espaço delimitado pela decídua capsular. Estes endodermas apresentaram formato prismático e encontraram-se separados do trofoblasto por uma desenvolvida membrana de Reichert. Já o endoderma visceral continha vasos vitelínicos e possuía vilosidades apenas em determinadas áreas. No décimo terceiro dia, foi possível estabelecer como condição primordial antes da inversão, a permanência de pelo menos um dentre os três elementos que caracterizavam a onfalopleura bilaminar. No décimo quarto dia de gestação verificou-se a inversão do saco vitelino, caracterizada pela degeneração do endoderma parietal e trofoblasto mural, associado ao desaparecimento gradual da membrana de Reichert. Como consequência deste fenômeno, o endoderma visceral passou a constituir interface com o epitélio uterino. Após a inversão, o endoderma parietal que permaneceu íntegro foi aquele que se apoiava na superfície da placenta principal, apresentando células em formato colunar alto e característica de epitélio pseudoestratificado. O endoderma visceral apresentou numerosas vilosidades apicais principalmente em regiões próximas a placenta principal. A intensa vascularização desse endoderma foi evidenciada pela reação imunohistoquímica para vimentina e microscopia eletrônica de varredura. Com o contínuo desenvolvimento do embrião e placenta principal, observou-se o surgimento de importante área de aposição entre os endodermas visceral e parietal cuja capacidade proliferativa destas células foi demonstrada pela reação imunohistoquímica para o PCNA. Por conseguinte, concluiu-se que a inversão do saco vitelino representou uma disposição anatômica favorável ao desenvolvimento embrionário além de uma característica evolutiva nesta espécie de roedor.

No description available.

Telômeros são complexos DNA-proteína presentes nas extremidades dos cromossomos. Os telômeros se encurtam a cada divisão celular, sendo o comprimento telomérico, portanto, considerado um biomarcador do envelhecimento celular. Esse encurtamento é vinculado a diversas doenças relacionadas à idade avançada. Na doença de Alzheimer (DA), têm sido associados com diversas vias fisiopatológicas, como a neuroinflamação e o estresse oxidativo, porém seus mecanismos ainda são pouco conhecidos. A maioria dos estudos sobre comprimento telomérico na DA é realizada em DNA leucocitário, pouco se sabendo sobre seu estado no sistema nervoso central. O lítio é um importante estabilizador de humor, com efeitos neuroprotetores amplamente evidenciados, mas pouco se sabe sobre seu efeito na manutenção do comprimento telomérico. O objetivo do presente estudo foi avaliar o efeito do tratamento crônico com lítio no comprimento telomérico em diferentes regiões cerebrais (córtex parietal, hipocampo e epitélio olfatório) de camundongos triplo transgênicos para DA (3xTg-AD) e selvagens. Dezoito animais transgênicos e 22 selvagens foram tratados por oito meses com ração contendo 1,0 g (Li1) ou 2,0 g (Li2) de carbonato de lítio/kg, ou ração padrão (Li0). O comprimento telomérico do DNA extraído destes tecidos foi quantificado por PCR em tempo real. O tratamento crônico com lítio foi associado a telômeros mais longos no córtex parietal (Li1, p=0,04) e hipocampo (Li2, p=0,02) dos camundongos 3xTg-AD comparados com os respectivos selvagens. Nossos achados sugerem que o tratamento crônico com lítio afeta a manutenção do comprimento telomérico, mas que a magnitude desse efeito depende da concentração de lítio ministrada e das características do tecido envolvido. Esse efeito foi apenas observado quando comparando os animais triplo transgênicos com os selvagens, indicando que a presença da patologia, no caso a DA, se faz necessária para a modulação do comprimento telomérico promovida pelo lítio / Telomeres are DNA-protein complexes present in the extremities of chromosomes. Telomeres shorten at each cell division, being the telomere length, therefore, considered a cell aging biomarker. This telomere shortening is associated to several age-related diseases. In Alzheimer\'s disease (AD), telomere length has been linked to several pathophysiological pathways, such as neuroinflammation and oxidative stress, though its mechanism are still poorly understood. Majority of studies regarding telomere length in AD are based in leucocyte DNA, with little information about its status in the central nervous system. Lithium is an important mood stabilizer, with neuroprotective effects widely evidenced, but little is known about its effects in telomere length maintenance. The objective of this present study was to evaluate the effect of chronical lithium treatment on telomere length in different brain regions (parietal cortex, hippocampus and olfactory epithelium) of wild type and triple transgenic mice model for AD (3xTg-AD). Eighteen transgenic and 22 wild type male mice were treated for eight months with chow containing 1.0g (Li1) or 2.0g (Li2) of lithium carbonate/kg, or standard chow (Li0). Telomere length of extracted DNA from theses tissues was quantified by real-time PCR. Chronic lithium treatment was associated with longer telomeres in the parietal cortex (Li1, p=0.04) and in the hippocampus (Li2, p=0.02)of 3xTg-AD compared with the respective wild type.Our findings suggest that chronic lithium treatment does affect telomere maintenance, but the magnitude of this effect depends on the working concentrations of lithium and characteristics of the involved tissue. This effect was only observed when comparing triple transgenic with wild type mice, suggesting that the presence of AD pathology was required for the lithium modulation of telomere length