La perception de mouvements est associée à une augmentation de l’excitabilité du cortex moteur humain. Ce système appelé « miroir » sous-tendrait notre habileté à comprendre les gestes posés par une tierce personne puisqu’il est impliqué dans la reconnaissance, la compréhension et l’imitation de ces gestes. Dans cette étude, nous examinons de quelle façon ce système miroir s’implique et se latéralise dans la perception du chant et de la parole. Une stimulation magnétique transcrânienne (TMS) à impulsion unique a été appliquée sur la représentation de la bouche du cortex moteur de 11 participants. La réponse motrice engendrée a été mesurée sous la forme de potentiels évoqués moteurs (PÉMs), enregistrés à partir du muscle de la bouche. Ceux-ci ont été comparés lors de la perception de chant et de parole, dans chaque hémisphère cérébral. Afin d’examiner l’activation de ce système moteur dans le temps, les impulsions de la TMS ont été envoyées aléatoirement à l’intérieur de 7 fenêtres temporelles (500-3500 ms). Les stimuli pour la tâche de perception du chant correspondaient à des vidéos de 4 secondes dans lesquelles une chanteuse produisait un intervalle ascendant de deux notes que les participants devaient juger comme correspondant ou non à un intervalle écrit. Pour la tâche de perception de la parole, les participants regardaient des vidéos de 4 secondes montrant une personne expliquant un proverbe et devaient juger si cette explication correspondait bien à un proverbe écrit. Les résultats de cette étude montrent que les amplitudes des PÉMs recueillis dans la tâche de perception de chant étaient plus grandes après stimulation de l’hémisphère droit que de l’hémisphère gauche, surtout lorsque l’impulsion était envoyée entre 1000 et 1500 ms. Aucun effet significatif n’est ressorti de la condition de perception de la parole. Ces résultats suggèrent que le système miroir de l’hémisphère droit s’active davantage après une présentation motrice audio-visuelle, en comparaison de l’hémisphère gauche. / The perception of movements is associated with increased activity in the human motor cortex. This system underlies our ability to understand one’s actions, as it is implicated in the recognition, understanding and imitation of actions. In this study, we investigated the involvement and lateralization of this “mirror neuron” system (MNS) in the perception of singing and speech. Transcranial magnetic stimulation (TMS) was applied over the mouth representation of the motor cortex in 11 participants. The generated motor response was measured in the form of motor evoked potentials (MEPs), recorded from the mouth muscle. The MEPs were compared for the singing and speech conditions in each cerebral hemisphere. Furthermore, to investigate the time course of the MNS activation, TMS pulses were randomly emitted in 7 time windows (ranging from 500 to 3500 milliseconds after stimulus onset). The stimuli for the singing condition consisted in 4-second videos of singers producing a 2-note ascending interval. Participants had to judge whether the sung interval matched a written interval, previously presented on the screen. For the speech condition, 4-second videos of a person explaining a proverb were shown. Participants had to decide whether this explanation matched a written proverb previously displayed on the screen. Results show that the MEP amplitudes were higher after stimulation of the right hemisphere in the singing condition. More specifically, sending TMS pulses between 1000 and 1500 milliseconds over the right hemisphere yielded higher MEPs as compared to the left hemisphere. No effect was found in the speech condition. These results suggest that the right MNS is more activated after an audiovisual motor presentation compared to the left hemisphere.

Il apparaît, suite aux résultats de plusieurs études comportementales et d’imagerie cérébrale, que les hormones gonadiques peuvent moduler le fonctionnement cérébral chez la femme. Les asymétries cérébrales fonctionnelles (ACFs), en particulier, changeraient en fonction du niveau de progestérone et d’œstrogène. On a également observé que lorsque le taux d’œstrogène est bas, les performances aux tâches impliquant l’hémisphère droit sont améliorées. Par contre, les preuves de l’action physiologique de ces deux hormones sur le cerveau ne sont pas très nombreuses. Le peu d’études d’électrophysiologie cognitive qui ont porté sur les effets du cycle menstruel ont rapporté que la composante P300 y serait sensible. Aucune n’a cependant utilisé une tâche d’habileté spatiale ou de rotation mentale qui sont connues pour impliquer davantage l’hémisphère droit. Le but de la présente étude est de documenter les changements électrocorticaux reliés aux variations hormonales lors d’une tâche de rotation mentale. Notre hypothèse de départ est que le taux d’œstrogène influencera l’activité électrocorticale et la latéralisation. Les potentiels évoqués cognitifs ont été comparés chez les mêmes femmes (n=12) lors d’une tâche de rotation mentale, répétée à deux périodes du cycle menstruel. Nos résultats démontrent que la condition de rotation induit une latéralisation de l’activité pariétale, vers l’hémisphère gauche, quand le niveau d’œstrogène est bas. Par contre, lorsque le niveau d’œstrogène est élevé, il n’y a aucune latéralisation. Par ailleurs, nous avons observé une augmentation de l’amplitude de la P300 lors du niveau oestrogénique élevé. En conclusion, les fluctuations oestrogéniques du cycle menstruel ont un impact sur la latéralisation de l’activité électrocorticale, lors d’un effort de rotation mentale. / After many behavioral and some neuroimaging studies, it appears that the gonadic hormones can modulate the neuronal function of women's brain. In particular, the functional cerebral asymmetries can be affected by the level of progesterone and estrogens. It has been observed that when the level of estrogen is low, the performance at task that engages more the right hemisphere is enhanced. However, there is a lack of evidence for the physiological actions of these two hormones on the brain. The few event-related potential studies taking into account the menstrual cycle effects, had noticed that the component P300 can be affected. No electrophysiological study has used a mental rotation task or spatial ability tests which are known for their right hemisphere dominance. The aim of the present research is to document the effect of hormonal variations on the electrocortical activity, using a mental rotation task. Our hypothesis is that estrogen levels affect electrocortical activity and lateralization. The ERPs were compared in the same women (n = 12) during a mental rotation task, repeated over two periods of the menstrual cycle. Our results show a lateralization of the left parietal activity when estrogen levels are low and during the rotation. Whereas when the estrogen level is high, there is no lateralization. In addition, we observed an increase in the amplitude of P300 for this same high level. In conclusion, estrogens fluctuations associated with the menstrual cycle have an impact on the lateralization of electrocortical activity, when a mental rotation is needed.

A reabilitação da região posterior da mandíbula com implantes dentários é complexa, especialmente em casos de reabsorção óssea moderada a severa. Embora existam diversas possibilidades de tratamento para essa região, os implantes curtos e a lateralização tem se destacado como alternativas viáveis e de menor tempo de tratamento. O objetivo deste trabalho foi avaliar, comparativamente, o risco mecânico dos dois tratamentos mencionados, com especial atenção ao risco de perda óssea e de fratura do parafuso. Para tanto, foram processadas tomografias de mandíbulas e realizada engenharia reversa de implantes e componentes protéticos para reconstrução de modelos tridimensionais, a fim de simular o comportamento biomecânico de próteses parciais fixas de três elementos, suportadas por dois implantes, utilizando simulações com o Método dos Elementos Finitos. Os modelos de implantes utilizados foram baseados nos implantes MK III (Nobel Biocare), com 5 e 4 mm de diâmetro por 7 de comprimento, representando implantes curtos, e com 4 e 3.75 mm de diâmetro por 15 de comprimento, representando implantes sob tratamento de lateralização do nervo alveolar inferior. Modelos distintos foram confeccionados para representar implantes tratados em um estágio (carga imediata) e dois estágios (implantes osseointegrados). Todos os modelos receberam simulação prévia de pré-tensão, referente a tensão gerada pelo torque do parafuso. Um padrão de carga oclusal axial e outro com carga oclusal oblíqua em 45% foram simulados, resultando em 16 diferentes simulações. A análise dos resultados revelou que o risco mecânico para perda óssea na região periimplantar, quando analisados implantes colocados em dois estágios, é maior para tratamentos com implantes curtos. Entretanto, para implantes colocados em um estágio, o maior risco de perda óssea foi para os implantes colocados com lateralização do nervo alveolar inferior. Quanto aos resultados dos parafusos, embora não se observou claras tendências quando simuladas cargas axiais, sob cargas oblíquas, os implantes de maior diâmetro e menor comprimento tiveram o menor risco à fratura do parafuso. / The rehabilitation of the posterior region of the mandible with dental implants is complex, especially in cases of moderate to severe bone loss. While there are several treatment options for this region, the use of short implants and lateralization has emerged as viable alternatives with less treatment time. The objective of this study was to comparatively evaluate the mechanical risk of both treatments mentioned, with special attention to the risk of bone loss and screw fracture. For this, CT scans of mandibles were processed and implants and prosthetic components were reverse engineered for reconstruction of three dimensional models to simulate the biomechanical behavior of fixed partial dentures of three elements, supported by two implants, using simulations with the Finite Element Method. The models of implants were based on MK III implants (Nobel Biocare) with 5 and 4 mm in diameter by 7 mm in length, representing short implants, and 4 and 3.75 mm in diameter by 15 mm long, representing implants used in treatments with lateralization of the inferior alveolar nerve. Several models were modeled to represent implants treated in one stage (immediate load) and two stages (osseointegrated implants). All models were simulated with pre-stress concerning the stresses generated by the torque of the screw. Axial and oblique oclusal loads at 45% were simulated, resulting in 16 different simulations. The results showed that the mechanical risk for bone loss, when osseointegrated implants were analyzed, is greater for treatments with short implants. However, for implants placed in one stage, the increased risk of bone loss was for implants placed with lateralization of the inferior alveolar nerve. Concerning the results of screws, there were no clear trends when axial loads were simulated, however, under oblique loads, the implants of larger diameter and shorter length had the lowest risk of screw fracture.

Introdução: A lateralização atípica de linguagem (LAL) é mais frequentemente observada em indivíduos com epilepsia no hemisfério esquerdo. Pacientes com epilepsia secundária a esclerose mesial temporal (EMT) apresentam alta frequência de LAL. A presença de EMTE, diretamente ou por efeitos à distância, perturbaria a determinação típica de lateralidade de linguagem (LL). Estudos de LL com RMf, em populações homogêneas de pacientes com EMT são escassos. Os padrões regionais de reorganização, nesta população, assim como os fatores clínicos e funcionais associados à LAL são pouco conhecidos. Os objetivos deste estudo foram (1) Validar paradigma de linguagem em RMf capaz de ativar áreas frontais e temporais de linguagem (2) Avaliar LL regional, em população homogênea de pacientes com EMT e verificar o papel de variáveis clínicas e da atividade epileptiforme na determinação de LAL. Foram avaliados 46 pacientes com EMT unilateral (24 EMTE e 22 EMTD) e 24 controles saudáveis, destros. Todos os participantes foram submetidos a RMf de linguagem com paradigma de nomeação responsiva à leitura (NRL) desenvolvido em língua portuguesa. O paradigma foi eficaz em ativar áreas de linguagem. A correlação entre IL-RMf e IL-Wada foi estatisticamente significativa no GFM (0,387; p < 0,01); GFI (0,594, p < 0,001); GTS (0,357, p < 0,05); GTM (0,509, p < 0,001) e GTI (0,489, p < 0,001). Os pacientes foram classificados em discordantes e concordantes (EEG/RM), após monitorização prolongada por vídeo-EEG. As classificações individuais de LL do teste de Wada e RMf foram concordantes em 84%(GFM), 86% (GFI), 74%(GTS), 83%(GTM) e 86%(GTI) dos casos. A frequência de LAL variou de 17 a 33%, para EMTE; 14 a 17%, para EMTD e de 0 a 10%, no grupo controle. Os grupos EMTEc e EMTEd apresentaram menores valores de IL-RMf, em relação ao grupo controle no GFM e GFI (p <= 0.05). Adicionalmente, o grupo EMTEd apresentou menor IL-RMf no GTM (p <= 0.01) e GTI (p <= 0.05). O grupo EMTDd apresentou menor IL-RMf no GFM; GFI; GTM e GTI (p <= 0.05). A ocorrência de mais de 5 descargas/hora no período interictal associou-se a LAL no GFM (p <= 0.01). Início da epilepsia, maior tempo de epilepsia e presença de IPI não foram associadas a LAL. Concluiu-se que a presença de EMT associou-se a LAL nas regiões frontais e temporais, sugerindo reorganização de linguagem envolvendo amplas regiões cerebrais, distantes da zona epileptogênica. O achado de LAL observada no grupo EMTDd sugere que a atividade epileptiforme temporal esquerda pode influenciar a reorganização de linguagem, independentemente da presença de lesão estrutural à esquerda. A maior frequência de descargas à esquerda associou-se a LAL / Atypical language lateralization (ALL) is associated with left hemisphere epilepsy, especially in epilepsy secondary to left mesial temporal sclerosis (MTS). Recent findings indicate that MTS, directly or by an at-distance effect may disrupt typical language lateralization (LL). Language-fMRI investigations in homogeneous MTS populations are scarce. Frontal and temporal language reorganization patterns in this population remain incompletely understood, as well as clinical factors associated with ALL. Our objectives were (1) To validate an fMRI paradigm effective to activate frontal and temporal language areas (2) To evaluate regional LL patterns in a homogeneous population of MTS patients and to investigate clinical factors associated with ALL. We studied forty-six right-handed patients (24 left MTS and 22 right MTS) and 24 controls. Patients and controls were similar in age and gender. Left and right MTS groups were comparable in terms of clinical variables. All participants underwent a language fMRI with reading response-naming paradigm (RRN) task developed in Brazilian Portuguese. The task effectively activated frontal and temporal language areas, with a high concordance with the Wada test. All patients were classified as concordant and discordant after video-EEG monitoring. Correlation between Wada test and fMRI LIs was significant in MFG (0.387; p < 0.01); IFG (0.594, p < 0.001); STG (0.357, p < 0.05); MTG (0.509, p < 0.001) e ITG (0.489, p < 0.001). Individual LI classifications with Wada test and fMRI were concordant in 84%(MFG), 86% (IFG), 74%(STG), 83%(MTG) e 86%(ITG). The frequency of ALL was 17-33%, in left MTS; 14-17%, in right MTS and 0-10%, in controls. Both concordant and discordant-left MTS patients presented lower LI than controls in MFG and IFG (p<=0.05). Additionally, discordant left MTS group presented lower LI in MTG (p<=0.01) and ITG (p<=0.05). Discordant right MTS group presented lower LI in MFG; IFG; MTG and ITG (p <= 0.05). Interictal left-sided spike frequency (< 5/h) was associated with lower LI (p <= 0.01) in MTG. In conclusion, MTS was associated with frontal and temporal language reorganization. Presence of ALL in discordant RMTS group suggests that left temporal epileptic activity may influence language reorganization, even in the absence of a left structural lesion. Higher left-sided spike frequency in MTS was associated with a left-right shift of speech representation

Despite considerable research, the effects of common types of noise on verbal and spatial information processing are still relatively unknown. Three experiments, using convenience sampling were conducted to investigate the effect of auditory interference on the cognitive performance of 24 adult men and women during the Stroop test, perception of object recognition and spatial location tasks, and the perception of object size, shape, and spatial location tasks. The data were analyzed using univariate analysis of variance and 1-way multivariate analysis of variance. The Experiment 1 findings indicated reaction time performance for gender and age group was affected by auditory interference between experimental conditions, and recognition accuracy was affected only by experimental condition. The Experiment 2a results showed reaction time performance for recognizing object features was affected by auditory interference between age groups, and recognition accuracy by experimental condition. The Experiment 2b results demonstrated reaction time performance for detecting the spatial location of objects was affected by auditory interference between age groups. In addition, reaction time was affected by the type of interference and spatial location. Further, recognition accuracy was affected by interference condition and spatial location. The Experiment 3 findings suggested reaction time performance for assessing part-whole relationships was affected by auditory interference between age groups. Further, recognition accuracy was affected by interference condition between experimental groups. This study may create social change by affecting the design of learning and workplace environments, the neurological correlates of auditory and visual stimuli, and the pathologies of adults such as attention deficit hyperactivity disorder.

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.

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.

Il apparaît, suite aux résultats de plusieurs études comportementales et d’imagerie cérébrale, que les hormones gonadiques peuvent moduler le fonctionnement cérébral chez la femme. Les asymétries cérébrales fonctionnelles (ACFs), en particulier, changeraient en fonction du niveau de progestérone et d’œstrogène. On a également observé que lorsque le taux d’œstrogène est bas, les performances aux tâches impliquant l’hémisphère droit sont améliorées. Par contre, les preuves de l’action physiologique de ces deux hormones sur le cerveau ne sont pas très nombreuses. Le peu d’études d’électrophysiologie cognitive qui ont porté sur les effets du cycle menstruel ont rapporté que la composante P300 y serait sensible. Aucune n’a cependant utilisé une tâche d’habileté spatiale ou de rotation mentale qui sont connues pour impliquer davantage l’hémisphère droit. Le but de la présente étude est de documenter les changements électrocorticaux reliés aux variations hormonales lors d’une tâche de rotation mentale. Notre hypothèse de départ est que le taux d’œstrogène influencera l’activité électrocorticale et la latéralisation. Les potentiels évoqués cognitifs ont été comparés chez les mêmes femmes (n=12) lors d’une tâche de rotation mentale, répétée à deux périodes du cycle menstruel. Nos résultats démontrent que la condition de rotation induit une latéralisation de l’activité pariétale, vers l’hémisphère gauche, quand le niveau d’œstrogène est bas. Par contre, lorsque le niveau d’œstrogène est élevé, il n’y a aucune latéralisation. Par ailleurs, nous avons observé une augmentation de l’amplitude de la P300 lors du niveau oestrogénique élevé. En conclusion, les fluctuations oestrogéniques du cycle menstruel ont un impact sur la latéralisation de l’activité électrocorticale, lors d’un effort de rotation mentale. / After many behavioral and some neuroimaging studies, it appears that the gonadic hormones can modulate the neuronal function of women's brain. In particular, the functional cerebral asymmetries can be affected by the level of progesterone and estrogens. It has been observed that when the level of estrogen is low, the performance at task that engages more the right hemisphere is enhanced. However, there is a lack of evidence for the physiological actions of these two hormones on the brain. The few event-related potential studies taking into account the menstrual cycle effects, had noticed that the component P300 can be affected. No electrophysiological study has used a mental rotation task or spatial ability tests which are known for their right hemisphere dominance. The aim of the present research is to document the effect of hormonal variations on the electrocortical activity, using a mental rotation task. Our hypothesis is that estrogen levels affect electrocortical activity and lateralization. The ERPs were compared in the same women (n = 12) during a mental rotation task, repeated over two periods of the menstrual cycle. Our results show a lateralization of the left parietal activity when estrogen levels are low and during the rotation. Whereas when the estrogen level is high, there is no lateralization. In addition, we observed an increase in the amplitude of P300 for this same high level. In conclusion, estrogens fluctuations associated with the menstrual cycle have an impact on the lateralization of electrocortical activity, when a mental rotation is needed.

La perception de mouvements est associée à une augmentation de l’excitabilité du cortex moteur humain. Ce système appelé « miroir » sous-tendrait notre habileté à comprendre les gestes posés par une tierce personne puisqu’il est impliqué dans la reconnaissance, la compréhension et l’imitation de ces gestes. Dans cette étude, nous examinons de quelle façon ce système miroir s’implique et se latéralise dans la perception du chant et de la parole. Une stimulation magnétique transcrânienne (TMS) à impulsion unique a été appliquée sur la représentation de la bouche du cortex moteur de 11 participants. La réponse motrice engendrée a été mesurée sous la forme de potentiels évoqués moteurs (PÉMs), enregistrés à partir du muscle de la bouche. Ceux-ci ont été comparés lors de la perception de chant et de parole, dans chaque hémisphère cérébral. Afin d’examiner l’activation de ce système moteur dans le temps, les impulsions de la TMS ont été envoyées aléatoirement à l’intérieur de 7 fenêtres temporelles (500-3500 ms). Les stimuli pour la tâche de perception du chant correspondaient à des vidéos de 4 secondes dans lesquelles une chanteuse produisait un intervalle ascendant de deux notes que les participants devaient juger comme correspondant ou non à un intervalle écrit. Pour la tâche de perception de la parole, les participants regardaient des vidéos de 4 secondes montrant une personne expliquant un proverbe et devaient juger si cette explication correspondait bien à un proverbe écrit. Les résultats de cette étude montrent que les amplitudes des PÉMs recueillis dans la tâche de perception de chant étaient plus grandes après stimulation de l’hémisphère droit que de l’hémisphère gauche, surtout lorsque l’impulsion était envoyée entre 1000 et 1500 ms. Aucun effet significatif n’est ressorti de la condition de perception de la parole. Ces résultats suggèrent que le système miroir de l’hémisphère droit s’active davantage après une présentation motrice audio-visuelle, en comparaison de l’hémisphère gauche. / The perception of movements is associated with increased activity in the human motor cortex. This system underlies our ability to understand one’s actions, as it is implicated in the recognition, understanding and imitation of actions. In this study, we investigated the involvement and lateralization of this “mirror neuron” system (MNS) in the perception of singing and speech. Transcranial magnetic stimulation (TMS) was applied over the mouth representation of the motor cortex in 11 participants. The generated motor response was measured in the form of motor evoked potentials (MEPs), recorded from the mouth muscle. The MEPs were compared for the singing and speech conditions in each cerebral hemisphere. Furthermore, to investigate the time course of the MNS activation, TMS pulses were randomly emitted in 7 time windows (ranging from 500 to 3500 milliseconds after stimulus onset). The stimuli for the singing condition consisted in 4-second videos of singers producing a 2-note ascending interval. Participants had to judge whether the sung interval matched a written interval, previously presented on the screen. For the speech condition, 4-second videos of a person explaining a proverb were shown. Participants had to decide whether this explanation matched a written proverb previously displayed on the screen. Results show that the MEP amplitudes were higher after stimulation of the right hemisphere in the singing condition. More specifically, sending TMS pulses between 1000 and 1500 milliseconds over the right hemisphere yielded higher MEPs as compared to the left hemisphere. No effect was found in the speech condition. These results suggest that the right MNS is more activated after an audiovisual motor presentation compared to the left hemisphere.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T19:35:48Z No. of bitstreams: 1 DissNSC.pdf: 1757369 bytes, checksum: 8c5c3122b8536a2aa61fd673039785e3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T19:35:55Z (GMT) No. of bitstreams: 1 DissNSC.pdf: 1757369 bytes, checksum: 8c5c3122b8536a2aa61fd673039785e3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T19:36:03Z (GMT) No. of bitstreams: 1 DissNSC.pdf: 1757369 bytes, checksum: 8c5c3122b8536a2aa61fd673039785e3 (MD5) / Made available in DSpace on 2017-08-23T19:36:10Z (GMT). No. of bitstreams: 1 DissNSC.pdf: 1757369 bytes, checksum: 8c5c3122b8536a2aa61fd673039785e3 (MD5) Previous issue date: 2017-04-13 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Stressful situations are risk factors to the development of neuropsychiatric diseases, as anxiety disorders. However, not everyone who experiences stressful events develops stress-related illness. That is due to the existence of differences in the ability to adapt to stress, that is, the manifestation of susceptibility or resilience phenotypes. The search for understanding neural systems involved to these differences has evidenced an important role of the medial Prefrontal Cortex (mPFC), and, recently, its functional lateralization has been highlighted. In this sense, the right mPFC (RmPFC) seems to modulate anxiogenic-like responses, while the left mPFC (LmPFC) would attenuate such responses, thereby facilitating animals to cope with threatening situations. If so, LmPFC inhibition would intensify ansiogenic-like behavior front to aversive stimuli. Under this hypothesis, one of the goals of the present study was to investigate whether the inhibition of the LmPFC could modulate the effect of two types of stress (the restraint and the social defeat) on anxiety. Yet, we also aimed to investigate whether NMDA-glutamate receptor would be involved to the anxiogenic-like effect induced by nitrergic activation of the RmPFC, given the anxiogenic potential of glutamate and the interaction already known between these neurotransmissions. To reach that, experiments were carried out (1) to characterize the effects of social defeat and restraint stress on animals exposed to elevated plus maze (EPM) 5 minutes or 24 hours later; (2) to evaluate the effects of restraint or social defeat combined to the synaptic inactivation (through nonspecific inhibitor, CoCl2) of the LmPFC on the defensive behavior of mice exposed to EPM 24 h after stress; (3) to investigate the effects of NMDA receptor antagonism and (4) the effect of that antagonism on anxiogenic-like effects induced by NO donor. The results showed that both restraint and defeat stress are anxiogenic at 5 minutes, but defeated mice do not display anxiety 24 h after stress. Furthermore, the synaptic inhibition produced a clear anxiogenic-like effect in defeated (but not restrained) mice. In addition, the blockade of NMDA receptors produced anxiolytic-like effects and reversed the anxiogenic effect induced by NO injection into the RmPFC. Taken together, these results corroborate previous studies demonstrating the functional lateralization of the mPFC, in which the right and left hemispheres seem to have distinct roles in the modulation of aversive events. / O estresse, que pode ser definido como uma condição que perturba o equilíbrio fisiológico e psicológico de um indivíduo, é fator de risco para o desenvolvimento de doenças neuropsiquiáticas, como transtornos de ansiedade. No entanto, nem todos os indivíduos que vivenciam um evento estressor desenvolvem doenças relacionadas a ele. Isto se deve à existência de diferenças na habilidade de se adaptar ao estresse, ou seja, a manifestação dos fenótipos de susceptibilidade ou resiliência. A busca pelo entendimento dos sistemas neurais envolvidos nessas diferenças tem evidenciado um papel importante do Córtex Pré-Frontal medial (CPFm) e, mais recentemente, a sua lateralização funcional vem ganhando especial destaque. Neste sentido, o CPFm Direito (D) parece modular respostas ansiogênicas, enquanto o CPFm Esquerdo (E) atenuaria essas respostas, ajudando o animal a lidar com eventos aversivos. Neste caso, a inibição do CPFmE intensificaria as respostas geradas por situações ameaçadoras. Sob essa hipótese, um dos objetivos do presente trabalho foi investigar se a inibição do CPFmE poderia modular o efeito de dois tipos de estresse (a contenção e a derrota social) sobre a ansiedade. Ainda, esse estudo também investigou se os receptores glutamatérgicos do tipo NMDA (N-metil-D-aspartato) estariam envolvidos no efeito ansiogênico provocado pela ativação nitrérgica [com injeção local do doador de óxido nítrico (NO), o NOC-9] no CPFmD, haja vista o potencial ansiogênico do glutamato e as interações já conhecidas entre essas neurotransmissões. Para tanto, foram feitos experimentos para (1) caracterizar os efeitos imediatos (após 5 minutos) ou tardios (após 24 horas) do estresse de derrota social e de contenção sobre o comportamento de animais expostos ao labirinto em cruz elevado (LCE); (2) avaliar os efeitos da combinação do estresse de contenção ou de derrota social com a inativação sináptica (através do inibidor inespecífico, CoCl2) do CPFm E no comportamento defensivo de camundongos expostos ao LCE 24h após o evento estressor; (3) investigar os efeitos do antagonismo per se de receptores NMDA e (4) o efeito desse antagonismo sobre a ansiogênese provocada pelo doador de NO sobre o comportamento de animais expostos ao LCE. Os resultados obtidos demonstram que ambos os estressores são ansiogênicos aos 5 minutos, mas a derrota social não provoca aumento de ansiedade 24 h após o estresse. Ainda, a inbição sináptica do CPFmE produz efeito ansiogênico 24 h depois quando associada ao estresse de derrota social (mas não à contenção). Além disso, o bloqueio de receptores NMDA por si provoca efeito ansiolítico e reverte o efeito ansiogênico provocado pelo NO em animais expostos ao LCE. Tomados em conjunto, esses resultados substanciam as evidências sobre a lateralização funcional do CPFm, em que os hemisférios direito e esquerdo parecem possuir diferentes participações na modulação de eventos aversivos.