La stimulation transcrânienne par courant continu (tDCS) sert à moduler l’activité neuronale. Elle consiste à appliquer un faible courant constant entre deux électrodes placées sur le cuir chevelu. Deux montages semblent efficaces pour moduler les capacités cognitives et/ou soulager des symptômes cliniques. Cependant, les effets neurobiologiques de la tDCS sont encore mal connues. Ce travail de thèse a tenté de clarifier les mécanismes cérébraux de la tDCS chez les sujets sains, en particulier en lien avec le système dopaminergique. En utilisant un design randomisée en double aveugle, nous avons combiné une session de tDCS online avec plusieurs modalités d'imagerie (PET ou PET-IRM simultanée) chez le sujet au repos. Une première étude (n=32, 2mA, 20min) a montré que la tDCS bifrontale induit une augmentation de la dopamine extracellulaire dans le striatum ventral, impliqué dans le réseau de récompense-motivation, après la stimulation. Une seconde étude (n=30, 1mA, 30min) a montré que la tDCS fronto-temporale induit une augmentation de la dopamine extracellulaire dans la partie exécutive du striatum et une diminution de la perfusion dans une région du réseau du default mode (DMN), après la stimulation. L'analyse des données de cette étude est toujours en cours. Dans l’ensemble, ce travail fournit la preuve qu'une seule session de tDCS frontale peut impacter le système dopaminergique dans des régions connectées aux zones corticales stimulées. Par conséquent, les niveaux d'activité et réactivité dopaminergique doivent être de nouveaux éléments à considérer dans l’hypothèse globale de modulation de l’activité cérébrale par la tDCS frontale / Transcranial direct current stimulation (tDCS) is used to modulate neuronal activity in the brain. It consists in applying a small constant current between two electrodes placed over the scalp. Two frontal tDCS montages have shown promises in modulating cognitive abilities and/or helping to alleviate clinical symptoms. However, the effects of tDCS on brain physiology are still poorly understood. The aim of this thesis work was to clarify brain mechanisms underlying frontal tDCS in healthy subjects, specifically in relation to the dopaminergic system. Using a double blind sham-controlled design, we combined a single session of tDCS online with several imaging techniques (PET or simultaneous PET-MRI) with the subject at rest. A first study (n=32, 2mA, 20min) showed that bifrontal tDCS induced an increase in extracellular dopamine in the ventral striatum, involved in the reward-motivation network, after the stimulation period. A second study (n=30, 1mA, 30min) showed that fronto-temporal tDCS induced an increase in extracellular dopamine in the executive part of striatum as well as a decrease in perfusion in a region part of the default mode network (DMN), after the stimulation period. The data analysis of this study is still ongoing. Overall, the present work provides evidence that a single session of frontal tDCS impacts the dopaminergic system in regions connected to the stimulated cortical areas. Therefore, levels of dopamine activity and reactivity should be new elements to consider for a general hypothesis of brain modulation by frontal tDCS

Submitted by Edineia Teixeira (edineia.teixeira@unioeste.br) on 2018-02-20T18:39:49Z No. of bitstreams: 2 Claudia_Fioresi2016.pdf: 16935854 bytes, checksum: 8a451f765c75e7a45afddf0008ee2b4d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-02-20T18:39:49Z (GMT). No. of bitstreams: 2 Claudia_Fioresi2016.pdf: 16935854 bytes, checksum: 8a451f765c75e7a45afddf0008ee2b4d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / One of the media's functions is to communicate science constituting a discursive genre that we call dissemination of science communication. Also the Comics are considered a specific genre of discourse, which can be used as a teaching resource for science classes. This work was carried out by a production activity of comics, which aimed to grant the dissemination of science. The production of comic books was performed by high school students from a public school in the city of Toledo/PR, in order to investigate how these students divulge certain issues of Science. Initially, it was performed the analysis of two texts "Paradise Pesticides", the journal Science Today and "The Truth About Gluten," the Journal Superinteressante. Our intention was to make a critical reading and to find out how each issue was addressed by their authors. It was verified the presence or non-objectivity of indices and some didatizantes elements. Based on the analysis, we observed that the text relating to gluten has a greater amount of didatizantes elements which seek a closer relationship with the reader, but can lead to erroneous relations of science. The text of pesticides have fewer didatizantes elements, which makes it closer to science. These two texts were brought to the classroom for reading and discussion with students, who could then, build their own comics. Later, it was worked the analysis of Comics produced by the students, which was held based on the method of content analysis, following the premises of Bardin (2011). The speeches found in Science dissemination of texts provided to students reflected directly in the content of elaborate stories in which can be seen an uncritical reading of the text by students, representing reductive perceptions of Science and Technology. Finally, considerations can anticipate that it is important to conduct critical anaylisis of the dissemination of science texts in the classroom then students can develop a critical look at the reports in the media. / Uma das funções da mídia é comunicar a Ciência. A linguagem com que informa constitui um gênero discursivo que denominamos Divulgação Científica. Também as Histórias em Quadrinhos são consideradas um gênero específico de discurso e que pode ser utilizado como recurso didático para as aulas de Ciências. Neste trabalho foi realizada uma atividade de produção de histórias em quadrinhos que teve como subsídio a divulgação da ciência. A produção das histórias em quadrinhos foi realizada por estudantes do Ensino Médio de uma escola pública, do município de Toledo/PR, com vistas a investigar a forma como esses estudantes divulgariam determinado assunto da Ciência. Inicialmente realizamos a análise de dois textos, sendo “Paraíso dos Agrotóxicos”, da Revista Ciência Hoje e “A Verdade sobre o Glúten”, da Revista Superinteressante. Nosso intuito foi realizar uma leitura crítica e averiguar como cada assunto foi abordado pelos seus autores. Verificamos a presença/frequência ou não de índices de objetividade e de alguns elementos didatizantes. Com base nas análises, observamos que o texto referente ao glúten possui maior quantidade de elementos didatizantes e que buscam uma aproximação maior com o leitor, mas que podem induzir a relações equivocadas da ciência. O texto sobre os agrotóxicos tem menor quantidade de elementos didatizantes, o que o torna mais próximo da ciência. Esses dois textos foram levados à sala de aula para leitura e discussão com os estudantes, que, a partir deles, construíram suas histórias em quadrinhos. Posteriormente nos debruçamos sobre essas histórias em quadrinhos produzidas pelos estudantes para analisá-las, análise que foi realizada tendo como base o método da Análise de Conteúdo, seguindo os pressupostos de Bardin (2011). Os discursos apresentados nos textos de divulgação da ciência fornecidos aos estudantes se refletiram diretamente no conteúdo das histórias elaboradas, nas quais é possível perceber uma leitura acrítica do texto por parte dos estudantes, representando, assim, percepções reducionistas de Ciência e Tecnologia. Como considerações é possível antecipar que é importante a realização de leitura crítica de textos de Divulgação Científica em sala de aula, para que os estudantes possam desenvolver um olhar crítico sobre as informações veiculadas pela mídia.

Cochlea-Implantate sind Neuroprothesen, die es Gehörlosen ermöglichen, Zugang zu auditiver Information wieder zu erlangen. Allerdings ist das resultierende Signal stark verzerrt bzw. degradiert und eine erfolgreiche Adaptation oft unvollständig. Das Verständnis zugrundeliegender perzeptueller Lernprozesse ist somit von enormer klinischer Bedeutung. Perzeptuelles Lernen degradierter Sprache lässt sich mittels Noise-Vokodierung bei Hörgesunden simulieren. In Bildgebungsstudien konnte anhand funktioneller Magnetresonanztomographie gezeigt werden, dass perzeptuelles Lernen degradierter Sprache mit einer Aktivitätssteigerung im linken inferior frontal gyrus (IFG) und linken inferior parietal cortex (IPC) assoziiert war. Die vorliegende Studie untersucht den Einfluss von fazilitierender, nicht-invasiver Hirnstromstimulation (anodale transkranielle Gleichstromstimulation, tDCS) über dem linken IFG und linken IPC auf das perzeptuelle Lernen {\\itshape{Noise}}-vokodierter Sprache. Die Probanden trainierten die Diskrimination von Minimal- (\"Tisch\"- \"Fisch\") und identen (\"Tisch\"- \"Tisch\") Wortpaaren, während der erste Stimulus akustisch degradiert, der zweite in geschriebener Form präsentiert wurden. Vor und nach dem Training wurden die trainierten Stimuli und eine gleiche Anzahl untrainierter Stimuli präsentiert. Perzeptuelles Lernen wurde in unserer Studie als eine Verbesserung der Diskriminationsleistung untrainierter Wortpaare operationalisiert. Zudem wurde vor und nach dem Training ein Elektroenzephalogramm abgeleitet. Auf elektrophysiologischer Ebene wurde der Einfluss des Lernvorgangs und der tDCS auf die N400 untersucht, welche mit der Verarbeitung lexiko-semantischer Informationen assoziiert ist. Unsere Ergebnisse zeigen, dass eine anodale tDCS über dem linken IFG perzeptuelles Lernen stark degradierter Sprache fazilitierte, während bei einer Placebo- bzw. einer Stimulation über dem linken IPC kein perzeptuelles Lernen stattfand.

Avec le besoin croissant en bande-passante, les technologies dites de radio-cognitive sont de plus en plus étudiées par la communauté scientifique. L’enjeu est d’utiliser au mieux le spectre disponible. L'une de ces technologies, Transform Domain Communication System (TDCS), dont les performances en termes d’efficacité énergétique et spectrale étaient jusqu'à présent méconnues, constitue le sujet d'étude de cette thèse. Après une présentation du contexte scientifique et industriel de la thèse, le système TDCS est introduit, ainsi que ses similarités et différences avec OFDM et MC-CDMA. Le système est ensuite décrit sous le formalisme algébrique des modulations linaires. Cela a permis d’établir une expression de l’efficacité spectrale du système. Plusieurs techniques sont alors proposées pour améliorer celle-ci tout en améliorant, dans certains cas, le taux d’erreur binaire. Étant composé d’un de plusieurs composantes sinusoïdales, le signal TDCS souffre d’un fort Peak-to-Average Power Ratio (PAPR). La théorie ensembliste est alors présentée puis mise à profit en troisième partie de cette thèse pour proposer les algorithmes Douglas-Rachford et ROCS de réduction du PAPR des signaux TDCS. Ces algorithmes convergent plus rapidement et vers des valeurs plus basses que l’algorithme POCS précédemment utilisé dans la littérature / For about ten years, spectrum scarcity and the growing need of bandwidth have pushed the studies on cognitive-radio technologies to counter this waste. Among them: the Transform Domain Communication System (TDCS), on which this thesis focuses. Until now, TDCS’ performance in terms of spectral and power efficiency was largely unknown. After introducing the thesis’ industrial and scientific context, the TDCS is introduced and compared with popular technologies such as OFDM and MC-CDMA. The system is then studied by means of the linear modulations’ algebraic framework. This has led to the TDCS’ spectral efficiency determination and to new design rules to jointly achieve a better spectral efficiency and a lower BER. Several methods are then proposed to further increase the spectral efficiency by means of a dense multidimensional modulation. Since a TDCS signal is made of several sines, it suffers from a strong Peak-to-Average Power Ratio (PAPR). Set theoretic estimation is then introduced in a third part and new PAPR-reduction algorithms such as Douglas-Rachford and Reflection Onto Convex Sets are brought to light and achieve better performance than the usual POCS algorithm regarding to the convergence rate, as well as the achieved PAPR

Chronic neuropathic pain affects up to 8% of the United Kingdom population and is a difficult condition to manage. It is established and maintained through many mechanisms, including central sensitisation (CS) in the spinal cord and brainstem. Neuropathic pain manifests as spontaneous pain, sensory loss and evoked hypersensitivity. The development of novel treatments for neuropathic pain is challenging, in part due to inadequate experimental models of clinically relevant pain. The use of functional magnetic resonance imaging (fMRI) techniques for imaging acute and increasingly tonic states enables the assessment of the neural correlates of evoked hypersensitivity and persistent pain, with the goal of developing appropriate biomarkers to test new therapies. This thesis develops novel techniques for the assessment of ongoing pain states and their modulation by therapies. We first identified a suitable human experimental model of CS using topical capsaicin, and an fMRI pipeline for the investigation of supraspinal involvement in pain hypersensitivity. In a placebo-controlled study, we then demonstrated the improved sensitivity of fMRI above subjective reports in detecting the efficacy of a known analgesic as compared to an ineffective active compound in a small cohort. To translate this to the more clinically relevant symptom of spontaneous pain, we developed and validated the use of a multi-inversion time pseudo-continuous arterial spin labelling (ASL) imaging and analysis pipeline for the neural assessment of tonic states and the absolute quantification of cerebral blood flow (CBF). Current evidence from structural and functional studies suggests a direct role for the posterior insula cortex in the encoding of nociception and pain. Using the ASL pipeline, we found that only a CBF change in the posterior insula region was correlated with the changing perception of persistent capsaicin-induced pain, and in a separate experiment showed that suppression of CBF in this region by gabapentin was related to the drug's suppression of subjective pain perception. We also demonstrated in a cohort of phantom limb patients that pain relief resulting from transcranial direct current stimulation of the deprived sensorimotor cortex is neurally represented by a decrease in posterior insula CBF. In a separate study, we showed that baseline CBF in the periaqueductal grey can predict individuals who are most vulnerable to pain and hypersensitivity following the induction of capsaicin-related CS. Taken together, these findings suggest that fMRI can be used as a tool to assess the efficacy of established and novel analgesics, with the midbrain reticular formation and posterior insula cortex being prime candidates as biomarkers of CS mechanisms and persistent pain respectively. Relatedly, ASL-fMRI may also be an effective technique for evaluating individuals' susceptibility to pain following inflammation or injury.

While fatigue is a common daily phenomenon, the exact relationship between perception of effort and fatigue is still unknown. Existing tools for assessing perception of effort are effectively limited to whole body exercise, while current methods for assessing voluntary activation are painful and not feasible for clinical application. The main aims of this thesis were to evaluate existing methodologies for their appropriateness in assessing perception of effort and voluntary activation following isolated muscle function testing, and to examine the relationship between subjective perception of effort and objective changes in the healthy motor control system. The implementation of reliable and valid assessment tools in clinical practice may enable clarification of the pathogenesis of many neurological conditions that have chronic fatigue as a key feature. Four studies of within-subjects repeated measures design have been conducted. Sixtynine healthy volunteers were recruited among staff and students of Brunel University. Magnetic stimulation was tested as a valid alternative to electrical stimulation in the conventional single-pulse Twitch Interpolation Technique. The 0–10 Numeric Rating Scale (NRS) was also tested for its reliability and validity in assessing the perception of effort during isometric exercise of elbow flexors. The changes of perception of effort following a submaximal elbow flexion fatiguing task, as well as following transcranial direct current stimulation (tDCS) over the motor cortex were also tested. The main findings showed significant differences between peripheral and magnetic stimulation in conventional single-pulse Twitch Interpolation Technique. The 0–10 NRS demonstrated linear properties and reported excellent test-retest reliability and good concurrent criterion validity in recording perception of effort under repeated isometric contractions of elbow flexors. Ten minutes of a submaximal intermittent isometric fatiguing exercise produced a significant elevation in rating of perceived effort, which was associated with central and peripheral neurophysiological changes of the motor control system. In contrast, perception of effort did not change significantly following 10 minutes of tDCS. The major findings of this thesis suggest the 0–10 NRS is a valid and reliable scale for rating perception of effort in healthy individuals. Further testing of the scale on patients is needed to establish its validity in clinical settings. Additionally, the findings indicate a substantial role of perception of effort in the voluntary motor control system. However, further research towards revealing the underlying mechanisms of perceived effort regulation in both health and disease is required.

No description available.

Introdução: Os opioides são os analgésicos mais efetivos para tratamento da dor moderada a intensa. No entanto, evidências crescentes têm demonstrado que seu uso pode levar a mudanças na sensibilidade dolorosa. Nesse contexto, a hiperalgesia induzida pelo remifentanil (r-IH) envolve um desequilíbrio nos sistemas inibitórios e excitatórios. Postula-se que um dos mecanismos centrais seja a disfunção do sistema modulador descendente da dor. Então, neste estudo, testamos a hipótese de que a estimulação transcraniana de corrente contínua (ETCC), devido aos seus efeitos analgésicos, poderia prevenir a r-IH. Os desfechos primários incluíram a escala numérica de dor (END 0-10) durante o teste repetitivo ao frio (rCOLDT), e a alteração na END (0-10) durante o teste de modulação condicionada de dor (CPM-TASK). Os desfechos secundários foram os limiares de dor ao calor (HPT) e o tempo de reação durante o teste de dor à água gelada [zero graus oC, (IPT)]. Métodos: Ensaio clínico randomizado, fatorial, duplo cego, que incluiu 48 homens saudáveis, com idades entre 19 e 40 anos. Os sujeitos foram randomizados em quatro grupos (n=12): ativo (a) - ETCC / solução salina, Sham (s) - ETCC / solução salina, a-ETCC / remifentanil e s-ETCC / remifentanil. Foi aplicado o ETCC sobre o córtex motor primário, com uma sessão única de 20 min e 2 mA. Resultados: Durante o rCOLDT, houve um efeito significativo entre os grupos nos escores cumulativos da END (P = 0,01). O grupo s-ETCC / remifentanil apresentou maiores escores de dor durante rCOLDT, [media (SD) 5,49 (1,04)] e a-ETCC / remifentanil apresentaram escores relativamente menores [4,15 (1,62)]. Este achado mostra que o efeito da ETCC bloqueou a HI-R. Os grupos a-ETCC / solução salina e s-ETCC / salina apresentaram menor índice de dor durante rCOLDT, [3.11 (1.2)] e [3.15 (1.62)], respectivamente. A incidência de hiperalgesia definida como um aumento de 15% na END durante o rCOLDT foi de: 31% no grupo s-ETCC/remifentanil; 22% no grupo a-ETCC/remifentanil; 11% no grupo a-ETCC/salina; e 8.3% no grupo s-ETCC/salina. Os grupos com remifentanil apresentaram escore positivo na END (0-10) durante a tarefa CPM, ou seja, produziu um desengate do sistema modulador descendente de dor (DPMS). Além disso, s-ETCC / Remifentanil em comparação com a-ETCC/remifentanil apresentou menor HPT e maior tempo de reação durante o IPT. Conclusão: Esses achados sugerem que os efeitos da a-ETCC previne a disfunção da capacidade inibitória do sistema modulador descendente da dor induzido pelo remifentanil durante o rCOLDT. / Background: Opioids are the most effective analgesics to treat moderate to severe pain. However, growing evidence shows that opioids can elicit unexpected changes in pain sensitivity. In this sense, remifentanil-induced hyperalgesia (r-IH) involves an imbalance in the inhibitory and excitatory systems. It postulates that one of the central mechanisms is the dysfunction of the descending pain modulating system. We tested the hypothesis that transcranial Direct Current Stimulation (t-DCS), given its analgesics effects, could prevent r-IH. The primary outcomes included the Numerical Pain Score NPS (0-10) during the repetitive cold test (rCOLDT) and the change on the NPS (0-10) during the conditioned pain modulation (CPM)-task. The secondary outcomes were the heat pain threshold (HPT) and the reaction-time during the Ice-Water Pain Test (IPT). Methods: This double blinded, explanatory factorial randomized trial included 48 healthy males, ages ranging 19 to 40 years. They were randomized into four equal groups: active (a)-tDCS/saline, sham (s)-tDCS/saline, a-tDCS/remifentanil and s-tDCS/remifentanil. We applied tDCS over the primary motor-cortex, with a single session of 20 minutes and 2mA. Results: During the rCOLDT, there was a significant group effect on the cumulative NPS scores (P=0.01). The s-tDCS/remifentanil group presented larger pain scores during rCOLDT, [mean (SD) 5.49 (1.04)] and a-tDCS/remifentanil group had relative lower pain scores [4.15 (1.62)]; showing its blocking effect on r-IH. a-tDCS/saline and s-tDCS/saline groups showed lowest pain scores during rCOLDT, [3.11(1.2)] and [3.15(1.62)], respectively. The incidence of hyperalgesia defined as a 15% increase in NPS during rCOLDT was: 30.3% in the s-tDCS / remifentanil group; 22% in the a-tDCS / remifentanil group; 11% in the a- tDCS / saline group; 8.3% in the s-tDCS / saline group. Remifentanil groups showed positive scores in the NPS (0-10) during the CPM-task, that is, it produced a disengagement of the descending pain modulatory system (DPMS). Also, s- tDCS/Remifentanil compared to a-tDCS/Remifentanil showed lower HPT and larger reaction-time during the IPT. Conclusion: These findings suggest that the effects of a-tDCS prevents the dysfunction of the inhibitory capacity of the descending modulatory pain system induced by remifentanil during rCOLDT.

With increasing life expectancy and global population of older adults, preserving cog- nitive function throughout life represents a growing priority. Numerous approaches to cognitive enhancement exist, but few have scientific merit. Among the most preva- lent – and commercialized – approaches are cognitive training (“brain training”) and non-invasive brain stimulation through electric currents applied at the surface of the scalp. The present dissertation describes a collection of work contextualizing the appeal of these cognitive enhancement methods and addressing some of the most pervasive limitations of research in this field thus far. One largely ignored issue in cognitive intervention research pertains to people’s expectations of programs and their relationship with intervention outcomes. In a series of initial studies, we developed and validated the Expectation Assessment Scale (EAS), a tool created to measure as well as prime expectations of outcomes in the context of cognitive enhancement interventions. In our first two studies, we probed expectations of cognitive training or non-invasive brain stimulation in over 1,000 young, middle-aged, and older adults. Ratings on the EAS suggested that older adults may have particularly high expectations of cognitive training, but that expectations can be primed to increase or decrease – at least in hypothetical scenarios. We used these data to assess the psychometric properties of the EAS with item-response theory, and confirmed its internal consistency. Next, we incorporated the EAS into two cognitive enhancement trials, one in- vestigating a computerized cognitive training intervention in nearly 100 older adults and another examining non-invasive brain stimulation in nearly 100 young adults. Both trials had a double-blind balanced-placebo design in which participants were assigned to the intervention or control condition, and then subdivided to receive ei- ther high or low expectation priming (i.e., primed to have high or low expectations of the program’s effectiveness). Although expectation ratings replicated our previous findings, results from these trials suggest little, if any, effect of either expectations or the intervention on performance outcomes. We nevertheless found that participants enjoyed their assigned program and that those who received high expectation prim- ing tended to report a more positive experience. Our findings put into question the effectiveness of such interventions and support the need for more rigorous trials of cognitive enhancement.

Tinnitus is the perception of sound in the absence of an actual sound stimulus. Recent developments have shifted the focus to the central nervous system and the neural correlate of tinnitus. Broadly, tinnitus involves cortical map rearrangement, pathological neural synchrony, and increased spontaneous firing rates. Various cortical regions, such as Heschl’s gyrus in the auditory cortex, have been found to be associated with different aspects of tinnitus, such as perception and loudness. I propose a cortical stimulation mapping study of Heschl’s gyrus using a depth and subdural electrode montage to conduct electrocorticography. This study would provide high-resolution data on abnormal frequency band oscillations characteristic of tinnitus and pinpoint regions where they occur. The validity of the neural synchrony model would also be tested in this study.