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Implementação de um sistema de localização espacial de regiões cerebrais em tempo real para aplicação de TMS por co-registro com fMRI; Implementation of a System for Real Time Space Localization of Cerebral Regions for TMS Application by MRI Co-Register

Peres, André Salles Cunha
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/04/2008 Português
Relevância na Pesquisa
37.44%
Nos últimos 20 anos tivemos um grande avanço na neurociência e nas técnicas de avaliação do sistema nervoso em humanos em uma tentativa inicial de compreensão de seu funcionamento. Colaboram com esse avanço técnicas como a eletroencefalografia (EEG), tomografia com-putadorizada (CT), tomografia por emissão de pósitron (PET), ressonância magnética funcional (fMRI), que geram mapas estatísticos de atividade cerebral, e a estimulação magnética transcrania-na (TMS), que se utiliza de pulsos de campo magnético, intensos e rápidos, de forma que a taxa de variação do fluxo magnético possa produzir uma estimulação cortical. No entanto a técnica de TMS ainda hoje utiliza parâmetros subjetivos para a determinação de um centro responsável por uma determinada atividade estimulada, os quais não possibilitam lo-calizar com precisão a região do córtex cerebral que está sendo estimulada por um pulso magnético. No intuito de eliminar essa subjetividade e estimularmos com precisão os centros de ativi-dade esse trabalho realiza um estudo do co-registro das técnicas de TMS e fMRI através de um neu-ronavegador que possibilita encontrar estruturas cerebrais sob uma determinada posição do escalpo. Inicialmente o estimulador foi caracterizado e um mapa de intensidade de campo magnético produ-zido pela bobina em forma de oito ou butterfly foi realizado por diferentes métodos. Em seguida um neuronavegador foi desenvolvido que permite fazer uma superposição das imagens de fMRI com o padrão de campos magnéticos produzido pela bobina. Pode-se variar a posição da bobina e observarem-se as regiões que provavelmente serão estimuladas pelo campo magnético. Com isso pode-se aperfeiçoar a estimulação. Para verificar a eficiência desse método estimulou-se o córtex motor de um grupo de 10 voluntários assintomáticos. O estímulo foi monitorado através de um eletromiógrafo posicionado no músculo abdutor do polegar da mão. Os resultados indicam que com o uso da neuronavegação foi possível estimular a região motora esperada em 100% dos voluntários estudados.; In the last 20 years we witnessed a great advance in neurosciences and evaluation techniques as an initial attempt for understanding of working principles of the human central nervous system Techniques such as electroencephalography (EEG)...

Desenvolvimento de protocolos de neuronavegação para estudos de estimulação magnética transcraniana e suas aplicações em voluntários controle e pacientes com acidente vascular cerebral; Development of protocols for Transcranial Magnetic Stimulation Neuronavigated studies and Its Applications in Control and Patients with Stroke subjects

Peres, André Salles Cunha
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/10/2012 Português
Relevância na Pesquisa
27.51%
Objetivos A estimulação magnética transcraniana (TMS, do inglês: Transcranial Magnetic Stimulation) e as imagens funcionais por ressonância magnética (fMRI, do inglês: functinal Magnetic Resonance Imaging) são duas técnicas não invasivas de investigação de atividade do sistema nervoso central. Porém essas duas técnicas utilizam estratégias diferentes para mensurar a atividade cerebral, sendo que a TMS avalia a resposta elétrica enquanto que a fMRI a resposta hemodinâmica. Nosso intuito nesse trabalho foi criar ferramentas para a comparação dessas duas técnicas no mapeamento do córtex motor, bem como utilizando as ferramentas desenvolvidas, fazer uma comparação dos mapas motores de pacientes com AVC com sujeitos assintomáticos, e nesses dois grupos, também realizar uma avaliação nos efeitos no córtex motor da eletroestimulação sensorial (SES, do inglês: Sensory Electric Stimulation) pelas técnicas de TMS e fMRI. Métodos Paro o mapeamento vetorial do campo magnético produzido pela bobina de TMS utilizamos fantomas que simulavam o tecido cerebral e realizamos medidas de imagens de ressonância magnética (MRI, do inglês: Magnetic Resonance Imaging) de fase em três direções para a construção do mapa vetorial. Uma vez dominada a técnica de mapeamento por imagens de fase...

Quantification of the TMS-EEG response in epilepsy

Santos, Maria Inês Fonseca Silva
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2012 Português
Relevância na Pesquisa
37.15%
Dissertação para obtenção do Grau de Mestre em Engenharia Biomédica; Purpose: The purpose of this thesis was to provide quantitative measures of the co-registration of transcranial magnetic stimulation (TMS) and electroencephalogram (EEG). The EEG is used to study changes in the neuronal activity evoked by the non-invasive technique TMS. These effects are determined mainly based on clinical judgment. Current uses in the diagnosis of epilepsy are based only on EEG, not taking into consideration the low sensitivity in the interictal period, in particular if routine recordings are used. Methods: Patient data was gathered, analyzed and compared to healthy controls. A total of ten patients and eighteen healthy subjects underwent sessions of 75 TMS pulses. The responses to the pulses were filtered and averaged. The use of topographical scalp plots of amplitude and power, and time-series analysis of power in search for late responses provide results which enable separation of epilepsy patients and healthy controls. By investigating the significance of the results it is also possible to determine, in a quantitative way how reliable the methods are for distinguishing between the two groups. Results: The definition of what is a response is critical in this project...

Interhemispheric Effect of Parietal TMS on Somatosensory Response Confirmed Directly with Concurrent TMS-fMRI

Blankenburg, Felix; Ruff, Christian C.; Bestmann, Sven; Bjoertomt, Otto; Eshel, Neir; Josephs, Oliver; Weiskopf, Nikolaus; Driver, Jon
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 03/12/2008 Português
Relevância na Pesquisa
27.44%
Transcranial magnetic stimulation (TMS) has been used to document some apparent interhemispheric influences behaviorally, with TMS over right parietal cortex reported to enhance processing of touch for the ipsilateral right hand (Seyal, Ro & Rafal, 1995). However, the neural bases of such apparent interhemispheric influences from TMS remain unknown. Here, we studied this directly by combining TMS with concurrent functional magnetic resonance imaging (fMRI). We applied bursts of 10-Hz TMS over right parietal cortex, at high or low intensity, during two sensory contexts: either without any other stimulation, or while participants received median-nerve stimulation to the right wrist, which projects to left primary somatosensory cortex (SI). TMS to right parietal cortex affected BOLD signal in left SI, with high-versus-low intensity TMS increasing the left SI signal during right-wrist somatosensory input, but decreasing this in the absence of somatosensory input. This state-dependent modulation of SI by parietal TMS over the other hemisphere was accompanied by a related pattern of TMS-induced influences in thalamus, as revealed by region-of-interest analyses there. A behavioral experiment confirmed that the same right-parietal TMS protocol of 10Hz bursts led to enhanced detection of peri-threshold electrical stimulation of the right median nerve...

Hemispheric differences in frontal and parietal influences on human occipital cortex: Direct confirmation with concurrent TMS-fMRI

Ruff, Christian C.; Blankenburg, Felix; Bjoertomt, Otto; Bestmann, Sven; Weiskopf, Nikolaus; Driver, Jon
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/2009 Português
Relevância na Pesquisa
27.42%
We used concurrent TMS-fMRI to test directly for hemispheric differences in causal influences of right or left fronto-parietal cortex on activity (BOLD signal) in human occipital cortex. Clinical data and some behavioral TMS studies have been taken to suggest right-hemisphere specialization for top-down modulation of vision in humans, based on deficits such as spatial neglect or extinction in lesioned patients, or findings that TMS to right (versus left) fronto-parietal structures can elicit stronger effects on visual performance. But prior to the recent advent of concurrent TMS and neuroimaging, it was not possible to directly examine the causal impact of one (stimulated) brain region upon others in humans. Here we stimulated frontal or intraparietal cortex in the left or right hemisphere with TMS, inside an MR scanner, while measuring with fMRI any resulting BOLD signal changes in visual areas V1-V4 and V5/MT+. For both frontal and parietal stimulation, we found clear differences between effects of right- versus left-hemisphere TMS on activity in visual cortex, with all differences significant in direct statistical comparisons. Frontal TMS over either hemisphere elicited similar BOLD-decreases for central visual field representations in V1-V4...

A Review of Combined TMS-EEG Studies to Characterize Lasting Effects of Repetitive TMS and Assess Their Usefulness in Cognitive and Clinical Neuroscience

Thut, Gregor; Pascual-Leone, Alvaro
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.46%
Transcranial magnetic stimulation (TMS) has developed into a powerful tool for studying human brain physiology and brain–behavior relations. When applied in sessions of repeated stimulation, TMS can lead to changes in neuronal activity/excitability that outlast the stimulation itself. Such aftereffects are at the heart of the offline TMS protocols in cognitive neuroscience and neurotherapeutics. However, whether these aftereffects are of applied interest critically depends on their magnitude and duration, which should fall within an experimentally or clinically useful range without increasing risks and adverse effects. In this short review, we survey combined TMS-EEG studies to characterize the TMS-aftereffects as revealed by EEG to contribute to the characterization of the most effective and promising repetitive TMS-parameters. With one session of conventional repetitive TMS (of fixed pulse frequency), aftereffects were consistently comparable in magnitude to EEG-changes reported after learning or with fatigue, and were short-lived (<70 min). The few studies using recently developed protocols (such as theta burst stimulation) suggest comparable effect-size but longer effect-durations. Based on the reviewed data, it is expected that TMS-efficacy can be further promoted by repeating TMS-sessions...

Occipital TMS has an activity-dependent suppressive effect

Perini, Francesca; Cattaneo, Luigi; Carrasco, Marisa; Schwarzbach, Jens V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 05/09/2012 Português
Relevância na Pesquisa
27.44%
The effects of transcranial magnetic stimulation (TMS) vary depending on the brain state at the stimulation moment. Four mechanisms have been proposed to underlie these effects: (i) virtual lesion–TMS suppresses neural signals; (ii) preferential activation of less active neurons–TMS drives up activity in the stimulated area, but active neurons are saturating, (iii) noise generation–TMS adds random neuronal activity and its effect interacts with stimulus-intensity; (iv) noise generation–TMS adds random neuronal activity and its effect depends on TMS-intensity. Here we explore these hypotheses by investigating the effects of TMS on early visual cortex on the contrast response function while varying adaptation state of the observers. We tested human participants in an orientation discrimination task, in which performance is contingent upon contrast sensitivity. Before each trial, neuronal activation of visual cortex was altered through contrast adaptation to two flickering gratings. In a factorial design, with or without adaptation, a single TMS pulse was delivered simultaneously with targets of varying contrast. Adaptation decreased contrast sensitivity. The effect of TMS on performance was state-dependent: TMS decreased contrast sensitivity in the absence of adaptation but increased it after adaptation. None of the proposed mechanisms can account for the results in their entirety...

Pre-Stimulus Sham TMS Facilitates Target Detection

Duecker, Felix; Sack, Alexander T.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 04/03/2013 Português
Relevância na Pesquisa
27.44%
Transcranial magnetic stimulation (TMS) allows non-invasive manipulation of brain activity during active task performance. Because every TMS pulse is accompanied by non-neural effects such as a clicking sound and somato-sensation on the head, control conditions are required to ensure that changes in task behavior are indeed due to the induced neural effects. However, the non-neural effects of TMS in the context of a given task performance are largely unknown and, consequently, it is unclear what constitutes a valid control condition. We explored the non-neural effects of TMS on visual target detection. Participants received single pulse sham TMS to each hemisphere at different time points prior to target appearance during a visual target detection task. It was hypothesized that the clicking sound of a sham TMS pulse differentially affects performance depending on the location of the coil and the timing of the pulse.Our results show that, first, sham TMS caused a facilitation of reaction times when preceding the target stimulus by 150, 200, and 250 ms, whereas earlier and later time windows were not effective. Second, positioning the TMS coil ipsilateral instead of contralateral relative to the target stimulus improved reaction times. Third...

Time- and Task-Dependent Non-Neural Effects of Real and Sham TMS

Duecker, Felix; de Graaf, Tom A.; Jacobs, Christianne; Sack, Alexander T.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/09/2013 Português
Relevância na Pesquisa
27.5%
Transcranial magnetic stimulation (TMS) is widely used in experimental brain research to manipulate brain activity in humans. Next to the intended neural effects, every TMS pulse produces a distinct clicking sound and sensation on the head which can also influence task performance. This necessitates careful consideration of control conditions in order to ensure that behavioral effects of interest can be attributed to the neural consequences of TMS and not to non-neural effects of a TMS pulse. Surprisingly, even though these non-neural effects of TMS are largely unknown, they are often assumed to be unspecific, i.e. not dependent on TMS parameters. This assumption is inherent to many control strategies in TMS research but has recently been challenged on empirical grounds. Here, we further develop the empirical basis of control strategies in TMS research. We investigated the time-dependence and task-dependence of the non-neural effects of TMS and compared real and sham TMS over vertex. Critically, we show that non-neural TMS effects depend on a complex interplay of these factors. Although TMS had no direct neural effects, both pre- and post-stimulus TMS time windows modulated task performance on both a sensory detection task and a cognitive angle judgment task. For the most part...

Non-invasive Transcranial Magnetic Stimulation (TMS) of the Motor Cortex for Neuropathic Pain—At the Tipping Point?

Treister, Roi; Lang, Magdalena; Klein, Max M.; Oaklander, Anne Louise
Fonte: Rambam Health Care Campus Publicador: Rambam Health Care Campus
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.27%
The term “neuropathic pain” (NP) refers to chronic pain caused by illnesses or injuries that damage peripheral or central pain-sensing neural pathways to cause them to fire inappropriately and signal pain without cause. Neuropathic pain is common, complicating diabetes, shingles, HIV, and cancer. Medications are often ineffective or cause various adverse effects, so better approaches are needed. Half a century ago, electrical stimulation of specific brain regions (neuromodulation) was demonstrated to relieve refractory NP without distant effects, but the need for surgical electrode implantation limited use of deep brain stimulation. Next, electrodes applied to the dura outside the brain’s surface to stimulate the motor cortex were shown to relieve NP less invasively. Now, electromagnetic induction permits cortical neurons to be stimulated entirely non-invasively using transcranial magnetic stimulation (TMS). Repeated sessions of many TMS pulses (rTMS) can trigger neuronal plasticity to produce long-lasting therapeutic benefit. Repeated TMS already has US and European regulatory approval for treating refractory depression, and multiple small studies report efficacy for neuropathic pain. Recent improvements include “frameless stereotactic” neuronavigation systems...

TMS affects moral judgment, showing the role of DLPFC and TPJ in cognitive and emotional processing

Jeurissen, Danique; Sack, Alexander T.; Roebroeck, Alard; Russ, Brian E.; Pascual-Leone, Alvaro
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.31%
Decision-making involves a complex interplay of emotional responses and reasoning processes. In this study, we use TMS to explore the neurobiological substrates of moral decisions in humans. To examining the effects of TMS on the outcome of a moral-decision, we compare the decision outcome of moral-personal and moral-impersonal dilemmas to each other and examine the differential effects of applying TMS over the right DLPFC or right TPJ. In this comparison, we find that the TMS-induced disruption of the DLPFC during the decision process, affects the outcome of the moral-personal judgment, while TMS-induced disruption of TPJ affects only moral-impersonal conditions. In other words, we find a double-dissociation between DLPFC and TPJ in the outcome of a moral decision. Furthermore, we find that TMS-induced disruption of the DLPFC during non-moral, moral-impersonal, and moral-personal decisions lead to lower ratings of regret about the decision. Our results are in line with the dual-process theory and suggest a role for both the emotional response and cognitive reasoning process in moral judgment. Both the emotional and cognitive processes were shown to be involved in the decision outcome.

Non invasive brain stimulation : modeling and experimental analysis of transcranial magnetic stimulations and transcranial DC stimulation as a modality for neuropathology treatment; TMS stimulations and tDCS as a modality for neuropathology treatment

Wagner, Timothy A. (Timothy Andrew), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 301 p.
Português
Relevância na Pesquisa
27.45%
This thesis will explore the use of Transcranial Magnetic Stimulation (TMS) and Transcranial DC Stimulation (tDCS) as modalities for neuropathology treatment by means of both experimental and modeling paradigms. The first and primary modality that will be analyzed is Transcranial Magnetic Stimulation (TMS). TMS is a technique that uses the principle of electromagnetic induction to focus induced currents in the brain and modulate cortical function. These currents can be of sufficient magnitude to depolarize neurons, and when these currents are applied repetitively (repetitive Transcranial Magnetic Stimulation (rTMS)) they can modulate cortical excitability, decreasing or increasing it, depending on the parameters of stimulation. This thesis will explore important facets of the electromagnetic field distributions and fundamental electromagnetic interactions to lay the foundation for future development of a more complete neural model and improved stimulation techniques. First, TMS will be analyzed as a technique used in normal healthy subjects. Finite element modeling (FEM) studies will be explored for realistic healthy human head models with a particular focus placed on the TMS induced cortical currents and their dependency on coil position...

Methodological Improvements in Combining TMS and Functional MRI; Methodologische Optimierung für kombinierte TMS und fMRT Anwendungen

Moisa, Marius
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
27.55%
Since 1997, when Bohning and colleagues demonstrated for the first time the feasibility of interleaving transcranial magnetic stimulation (TMS) with blood oxygenation level dependency functional magnetic resonance imaging (BOLD fMRI), this combination became a very promising techniques to study brain connectivity. However, the implementation of a reliable setup for interleaved TMS/fMRI is still technically challenging. In this thesis, I intended to further explore and develop methodological improvements in combining TMS and fMRI and to apply them in order to better understand the neural underpinnings of the behavioral TMS effects and to study brain connectivity. First, I developed and validated a new hardware/software coil positioning method for interleaved TMS/fMRI and demonstrated the feasibility of our overall setup. Second, a setup for combining TMS with continuous arterial spin labeling (CASL) was implemented and I tested the feasibility of this novel combination. Third, I demonstrated that this combination is sensitive enough to reliably measure rCBF changes induced by TMS, and that interleaved TMS/CASL can detect differences between the effects on regional cerebral flow (rCBF) of two different stimulation protocols. Fourth, it was shown that interleaved TMS/CASL is suitable to target questions from cognitive neuroscience. It was demonstrated that TMS applied over left dorsal premotor cortex (PMd) has different effects on the remote rCBF activation depending on the motor task. Overall...

Selbstregulation langsamer Hirnpotentiale (SCP) nach transkranieller Magnetstimulation (TMS); Modulation of slow cortical potentials by transcranial magnetic stimulation in humans

Schmidt, Konrad-Friedrich Reinhart
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
37.45%
Die Arbeiten von Birbaumer et al. haben in Vergangenheit hinreichend gezeigt, daß die langsamen Komponenten (SCPs) des Elektroenzephalogrammes bewußt kontrolliert werden können. Auf Grundlage dieses Effektes konnte eine Kommunikationshilfe für schwerstgelähmte Patienten konstruiert werden. Die transkranielle Magnetstimulation (TMS) ermöglicht eine schmerzlose und nichtinvasive Induktion von elektrischer Spannung in das menschliche Gehirn. Für wenige Millisekunden können durch ein starkes Magnetfeld ausgedehnte Kortexareale depolarisiert werden. Thema der vorliegenden Arbeit ist die Wechselwirkung von TMS mit der Selbstregulation langsamer Hirnpotentiale. Dreizehn gesunde Probanden und ein gelähmter Patient mit amyotropher Lateralsklerose (ALS) wurden durch visuelle Rückkoppelung trainiert, ihre SCPs selbst zu kontrollieren. Ihre Aufgabe bestand darin, auf ein Signal hin positive oder negative SCPs zu generieren. Ein Durchgang dauerte dabei 5 Sekunden und wurde bei Erfolg mit einer Bildschirmanzeige belohnt. Eine Sitzung bestand aus 70 Durchgängen, pro Proband wurden 27 Sitzungen durchgeführt. Die Potentiale wurden unipolar und zentral von der Elektrodenposition Cz abgeleitet. Neun der dreizehn Probanden erlernten die Selbstkontrolle über ihre langsamen Hirnpotentiale...

Der Einfluß der Stromrichtung auf motorische und visuelle Schwellen der transcraniellen Magnetstimulation; The influence of current direction on motor and visual thresholds by TMS

Beck, Sandra Christine
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
37.27%
Gegenstand der vorliegenden Arbeit war die Bestimmung von Schwellenwerten mit der TMS und die sich daraus ableitende Einschätzung der Erregbarkeit verschiedener kortikaler Areale. Als wichtiger Parameter hierfür gilt die motorische Schwelle, die mit Hilfe der transkraniellen Magnetstimulation bestimmt werden kann. Im motorischen System verwendeten wir ein bereits veröffentlichtes Messverfahren (Kammer et al., 2000). Aus-gehend von diesem Verfahren haben wir eine neue Messmethode für den visuellen Kortex entwickelt, die es ermöglicht, die Erregbarkeit von motorischem und visuellem Kortex zu vergleichen. In unseren Experimenten, die jeweils mit zwei verschiedenen Stimulationsgeräten durchgeführt wurden, variierten wir die Richtung des im Gehirn induzierten Stroms, die stimulierte Hemisphäre und äußere Faktoren, wie die Luminanz des Hintergrundes. Als wesentliches Ergebnis unserer Messungen zeigte sich, dass es im visuellen Kortex, wie im motorischen, eine Vorzugsstromrichtung gibt. Die Schwellenwerte waren signifikant niedriger, wenn der induzierte Strom von lateral nach medial, also horizontal und senkrecht zum Inter-hemisphärenspalt floß. Die Schwellen bei entgegengesetzter Stromrichtung lagen im Mittel 20% höher. Dieser Stromrichtungseffekt trat unab-hängig von der Hemisphäre und vom Stimulations-gerät auf. Die Luminanz des Hintergrundes (von Dunkelheit bis 3200 cd/m²) hatte keinen Einfluß auf die visuellen Schwellenwerte. Im Gegensatz zum "hot spot" des motorischen gab es im visuellen Kortex ein mehrere Quadrat-zentimeter umfassendes Areal...

Kortiko-spinale Reorganisation bei kongenitaler Hemiparese: Einfluss der Größe der Pyramidenbahnläsion bei periventrikulären Läsionen - eine Studie mit TMS und MRT; Cortico-spinal reorganization in congenital hemiparesis: Influence of the extent of pyramidal periventricular lesions – a TMS and MRI study

Stitz, Jutta Silvia
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
37.42%
Einleitung: Die neuronale Reorganisation nach frühen Hirnläsionen wird wesentlich durch die Faktoren Entstehungszeitpunkt, Lokalisation und Ausmaß der Läsion bestimmt. In der vorliegenden Arbeit wurde am Beispiel der Handmotorik die kortiko-spinale Reorganisation abhängig von der Läsionsgröße untersucht. Im Gegensatz zu den bisherigen Studien wurde hierzu ein Patientenkollektiv mit Läsionen einheitlicher Lokalisation und einheitlichen Entstehungszeitraums gewählt, nämlich Patienten mit kongenitaler Hemiparese aufgrund unilateraler periventrikulärer Läsionen (Entstehungszeitraum: 24.-36. Schwangerschaftswoche). Methode: Mittels TMS (Transkranielle Magnetstimulation) wurden neun Patienten (Alter: 16-23 Jahre) und acht gesunde Probanden (Alter: 19-33 Jahre) unter Verwendung einer Schmetterlingsspule mit fokaler Einzelpulstechnik über beiden Hemisphären stimuliert. Gleichzeitig wurden beidseits an den Unterarm-Extensoren die mittels TMS hervorgerufenen motorisch evozierten Potentiale (MEP) abgeleitet und deren Latenz gemessen. Ergebnisse: Es konnte gezeigt werden, dass die TMS-Ergebnisse sowohl mit der in einer Vorstudie (Staudt et al., Neuropediatrics 2000) kernspintomografisch ermittelten Ausdehnung der strukturellen Schädigung handmotorischer Pyramidenbahnfasern als auch mit dem Grad der motorischen Beeinträchtigung korrelieren: Bei TMS der geschädigten Hemisphäre konnten kontralaterale MEPs der paretischen Hand nur bei geringer und mäßig schwerer struktureller Schädigung ausgelöst werden. Bei mäßig schwerer und ausgeprägter Schädigung waren dagegen abnorme ipsi-laterale MEPs der paretischen Hand bei Stimulation der intakten Hemisphäre nachweisbar. Dabei unterschieden sich Latenzen und Stimulationsorte der ipsilateralen MEPs der paretischen Hand nicht wesentlich von denen der kontralateralen MEPs der nicht-paretischen Hand. Schlussfolgerung: Die Reorganisation des kortiko-spinalen Systems korreliert mit dem Ausmaß der Schädigung pyramidaler Nervenfasern im periventrikulären Marklager: Bei Patienten mit großen...

Neural Correlates of Perception for Action in Humans Using TMS and fMRI; Neuronale Korrelate der Perzeption zur Bewegungssteuerung beim Menschen untersucht mittels TMS und fMRI

Reichenbach, Alexandra
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
27.48%
Movements are humans interface to their social and physical environment. The human brain processes numerous complex computations during everyday actions, such as reaching for a door knob. It must recognize and localize the knob visually, and calculate its spatial relation to the hand. Then, the movement of the arm and hand with all their muscles has to be planned. During the movement, these parameters are monitored, and when the environment changes, for instance when the door is opened, the movement is adapted on the fly. Sensorimotor integration processes during a movement take 60-160ms, thus are much faster than processes for conscious perception. The mechanisms and cortical localization of these processes is the topic of the present dissertation. Perturbation paradigms are utilized for investigating reach adjustments: Participants have to reach for a target, and a perturbation, such as a displacement of the target, is introduced during the ongoing movement. Thus, the participant must adjust the movement, and the brain has to integrate the newly arriving sensory information into the current movement plan. The first project investigated the chronometry of the processes responsible for the integration of visual and proprioceptive information. I measured with electromyography (EMG) the neural latency from the perturbation to the response. This method provided the computation time necessary for integrating and transforming sensory to motor signals. Furthermore...

A Randomized, Controlled Investigation of Motor Cortex Transcranial Magnetic Stimulation (TMS) Effects on Quantitative Sensory Measures in Healthy Adults: Evaluation of TMS Device Parameters

Borckardt, Jeffrey J.; Reeves, Scott T.; Beam, Will; Jensen, Mark P.; Gracely, Richard H.; Katz, Sophie; Smith, A. Richard; Madan, Alok; Patterson, David; George, Mark S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
27.45%
There is emerging evidence that transcranial magnetic stimulation (TMS) can produce analgesic effects in clinical samples and in healthy adults undergoing experimentally induced pain, and the field of minimally invasive brain stimulation for the management of pain is expanding rapidly. While, motor cortex is the most widely used cortical target for TMS in the management of neuropathic pain, few studies have systematically investigated the analgesic effects of a full range of device parameters to provide initial hints about what stimulation intensities and frequencies are most helpful (or even potentially harmful) to patients. Further, there is considerable inconsistency between studies with respect to laboratory pain measurement procedures, TMS treatment parameters, sophistication of the sham methods, and sample-sizes. The present study employed a sham-controlled, within-subject, cross-over design to examine the effects of five different TMS treatment parameters across several quantitative sensory measures in a sample of healthy adult volunteers. 65 participants underwent quantitative sensory testing procedures pre- and post- 40-minutes of real and sham motor cortex TMS. TMS was delivered at 1Hz 80% resting motor threshold (rMT), 1Hz 100%rMT...

TMS-EEG combined with granger causality: an innovative information flow approach over the full brain connectivity

Fernandes, Tiago José Cardoso Pires Timóteo
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2015 Português
Relevância na Pesquisa
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Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015; Atualmente, no mundo das neurociências, a conectividade cerebral é um tema em destaque. Este conceito encontra-se dividido em conetividade estrutural (relações anatómicas entre estruturas cerebrais), conectividade funcional (dependências estatísticas entre estruturas cerebrais) e conectividade efetiva (relações de causalidade entre estruturas cerebrais). Esta tese debaterá fundamentalmente sobre o último destes conceitos, tentando oferecer uma interpretação para o fluxo de informações entre as áreas do cérebro. Muitas técnicas podem ser utilizadas na sua análise, entre os quais a Causalidade de Granger (GC) ou a estimulação magnética transcraniana em combinação com eletroencefalografia (TMS-EEG). Por um lado, a GC permite uma interpretação das ligações diretas dentro e fora das mesmas áreas cerebrais, sendo uma abordagem explicativa sobre os dados, onde não é necessária nenhuma hipótese sobre o comportamento das relações causais. No entanto, os resultados de GC são muito sensíveis, uma vez que dependem de sinais não-estacionários e não colineares, aspetos bastante presentes em sinais de eletroencefalografia (EEG). Desta forma...

γ-Lactones Upon Double Nucleophilic Additions of Bis(TMS)Ketene Acetals to Π-systems and Access to New-towards Cancer Cells Cytotoxic-Endoperoxide Lactones

Rudler,Henri; Aldeco-Pérez,Eugenia; Parlier,Andrée; Álvarez,Cecilio; Chaquin,Patrick; Herson,Patrick; Toscano,Alfredo; Ramírez-Apan,María-Teresa
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2008 Português
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Arenechromium and cycloheptatrienechromium complexes react with (TMS)ketene acetals to give upon a double nucleophilic addition either diene-lactones or cyclohexenone-lactones. In the first case, the scope of the reaction and the stability of the dienes were examined: they could be easily transformed either in arylpropionic acids or in conjugated ketones and more interestingly, they reacted with oxygen to give new highly active cytotoxic endoperoxide lactones. Unfortunately, in the second case, no further functionalization could be achieved up to now.