Littérature scientifique sur le sujet « Aging, Motor Imagery, fMRI »

We present a robotic embodiment experiment based on real-time functional magnetic resonance imaging (rt-fMRI). In this study, fMRI is used as an input device to identify a subject's intentions and convert them into actions performed by a humanoid robot. The process, based on motor imagery, has allowed four subjects located in Israel to control a HOAP3 humanoid robot in France, in a relatively natural manner, experiencing the whole experiment through the eyes of the robot. Motor imagery or movement of the left hand, the right hand, or the legs were used to control the robotic motions of left, right, or walk forward, respectively.

Aims. While studies on healthy subjects have shown a partial overlap between the motor execution and motor imagery neural circuits, few have investigated brain activity during motor imagery in stroke patients with hemiparesis. This work is aimed at examining similarities between motor imagery and execution in a group of stroke patients. Materials and Methods. Eleven patients were asked to perform a visuomotor tracking task by either physically or mentally tracking a sine wave force target using their thumb and index finger during fMRI scanning. MIQ-RS questionnaire has been administered. Results and Conclusion. Whole-brain analyses confirmed shared neural substrates between motor imagery and motor execution in bilateral premotor cortex, SMA, and in the contralesional inferior parietal lobule. Additional region of interest-based analyses revealed a negative correlation between kinaesthetic imagery ability and percentage BOLD change in areas 4p and 3a; higher imagery ability was associated with negative and lower percentage BOLD change in primary sensorimotor areas during motor imagery.

Motor imagery (MI) is a cognitive state in which movements are mentally evoked. There is behavioural evidence that MI declines with aging, but limited information on the functional anatomical correlates of these changes. In my thesis, I present a systematic behavioural/fMRI investigation of this issue and demonstrate that aging is associated with modified brain responses ranging from successful compensation to failed compensation depending on the complexity of the motor imagery task. After a theoretical introduction in Chapter 1, I describe the effects of early aging on explicit MI, through a study of 24 young and 24 elderly subjects during two fMRI tasks requiring movement execution (ME) or MI of finger movements; temporal correlations between MI and ME were also measured (Chapter 2). I found significant differences between the two groups: elderly subjects lost the behavioural temporal correlation between MI and ME; moreover, they over-recruited occipito-temporal areas. The temporal discrepancy between MI and ME in the elderly subjects correlated with brain regions that showed increased activations. These observations suggest that elderly subjects have qualitatively different explicit MI abilities. MI can be elicited also by using implicit tasks, in which subjects are involved in motorically driven decisions. The hand laterality task is one such example: subjects are asked to decide whether a depicted hand is a left or a right one. Chapter 3 illustrates the fMRI correlates of this task in 30 young subjects. I found stronger signals in left premotor and parietal cortices for palm-viewed stimuli, whereas back-view stimuli were associated with stronger occipital activations to suggest the existence of brain-encoded, view-dependent representations of body segments. Chapter 4 reports the extension of the 2nd study to the assessment of the effects of early aging on implicit motor processes: I compared those data with the ones of 29 elderly subjects. While there was no specific aging related behavioural effect, I found significant additional activations in the elderly group in occipito-temporal regions, which were negatively correlated with RTs. These results reveal a pattern of graceful aging in the domain of implicit motor representations whereby cognitive performance remains at juvenile level thanks to some compensatory brain processes. It remained to be seen whether the effect of early aging could be detected by using more complex implicit MI tasks, something addressed in Chapter 5, through the study of 22 young and 23 elderly subjects performing a Grip Selection Task in which they were asked to report whether they would grip a portrayed tool with an over- or an under-hand grip. I found a behavioural decline in the elderly group, with hyperactivations in the occipital cortices and hypoactivations in the superior parietal lobule, an area previously associated with object grasping. The greater complexity of the imagined movement may determine a pattern interpretable in terms of a failed attempt of compensation. I conclude with Chapter 6, discussing my data in the light of neurocognitive models of healthy aging.

La deambulazione è un comportamento altamente automatizzato e iperappreso, ma basato su programmi sensori motori complessi che coinvolgono numerosi centri nel tronco encefalico, nel cervelletto e nella corteccia. Il decadimento delle abilità di deambulazione è uno dei tratti che definiscono l’invecchiamento. L’osteoartrite per gli arti inferiori è considerato la maggior causa di disabilità e handicap nelle società occidentali industrializzati: è la causa maggiore di dolore muscolo scheletrico e a causa della grave limitazione funzionale molte attività della vita quotidiana sono compromesse. La comprensione della fisiologia del cammino a livello centrale, i cambiamenti dovuti all’invecchiamento o l’impatto di patologie periferiche su questa fisiologia è molto limitato. In questa tesi ho descritto una serie di esperimenti con lo scopo di comprendere meglio la fenomenologia del cammino negli anziani e definire quanto questa abilità e la sua rappresentazione mentale, evocata tramite specifici compiti, potesse essere influenzata dall’osteoartrite al ginocchio. Questa patologia è stata selezionata come modello di un deterioramento delle rappresentazioni del cammino a livello cortico/sottocorticale in assenza di chiari disturbi neurologici. Lo scopo a lungo termine di questa ricerca è dare un solido razionale per poter testare l’efficacia di una riabilitazione basata su strategie di immaginazione motoria nel recupero post chirurgico. Tramite gli esperimenti ho definito la neurofisiologia del cammino a livello centrale (sopraspinale) nell’immaginazione motoria e nell’immaginazione dell’imitazione, tramite l’uso della fMRI. Questo è stato fatto prima nei sani. Nel mio esperimento finale il pattern fMRI ottenuti per i soggetti sani sono stati confrontati con quelli di un gruppo di pazienti con osteoartrite del ginocchio. I punti principali possono essere così riassunti: (1) i pazienti con osteoartrite al ginocchio sono ancora capaci di eseguire compiti di immaginazione motoria che coinvolgono la deambulazione; (2) ciononostante sembra che i pazienti non siano stati in grado di incorporare la loro limitazione motoria periferica nella simulazione mentale della deambulazione in quanto risultano più veloci dei loro controlli sani; (3) i dati fMRI per i soggetti sani mostrano che l’immaginazione motoria per il cammino dipende da un grande pattern fronto-parietale a livello corticale e maggiori attivazioni a livello cerebellare e del tronco encefalico, in aree legate al cammino, rispetto all’immaginazione dell’imitazione.(4) Infine i dati fMRI per i pazienti con osteoartrite hanno mostrato maggiori attivazioni per aree coinvolte nell’immaginazione motoria quando il compito di immaginazione era combinato con un’esplicita simulazione della deambulazione ossia la dorsi-flessione delle caviglie. Insieme questi risultati (1) contribuiscono alla definizione dei pattern neurali coinvolti nell’immaginazione del cammino per cervelli sani, (2) dimostrano abilità qualitativamente differenti, ma ancora accessibili, nella rappresentazione della deambulazione per compiti di immaginazione motoria sia a livello comportamentale (3) che a livello anatomo-funzionale. Il razionale di questo studio lascia ipotizzare che l’uso dell’immaginazione motoria possa facilitare il recupero della deambulazione in pazienti con osteoartrite al ginocchio nel periodo post operatorio, magari aggiungendo qualche particolare aggiuntivo, come minimo comportamento motorio (come la dorsi-flessione della caviglia). Questo mi sarà possibile discuterlo nel momento in cui avrò terminato gli specifici esperimenti per l’uso dell’immaginazione motoria in riabilitazione.
Gait is a highly automatic behavior. Although walking is an over-experienced action, stance and locomotion are based on complex sensorimotor programs that involve several distinct and separate supraspinal centers in the brainstem, cerebellum and the cortex (l’italiano sarebbe: Gait is a highly automatic and over-experienced behavior, based on complex sensorimotor programs that involve several centers in the brainstem, cerebellum and the cortex). The decay of gait related skills is one of the defining traits of ageing. Osteoarthritis in the lower limbs is considered the single most important cause of disability and handicap in Western industrialized countries: it is the main cause of musculoskeletal pain, and daily life activities are reduced due to severe functional limitation. The comprehension of the central physiology of walking and its age-related changes or the impact of peripheral disease on this physiology is very limited. In the present thesis I describe a series of experiments whose aim was to better understand the phenomenology of walking in elderly people and to assess to what extent this skill and its mental representation, evoked through specific motor imagery tasks, can be affected by a peripheral disorder such as knee osteoarthritis. This disease was chosen as a model of possible deterioration of cortical/subcortical representations of walking behavior in the absence of obvious neurological disorders. The long-term goal of this research is also to test the beneficial effect of motor-imagery-based rehabilitation strategies in guiding post-surgery recovery of the patients. The present study aims at providing a strong rationale for this overarching goal. In the same series of experiments, I characterize the central (supraspinal) neurophysiology of walking using fMRI in motor imagery or imitation through imagery. This is done in normal subjects first. In my final experiment I compare the fMRI patterns of normal subjects with those of patients with knee osteoarthritis. The main points of my experiments can be summarized as follows: (1) patients with knee osteoarthritis are still capable of motor imagery for the walking behavior; (2) yet, they seem not to have incorporated their peripheral motor limitation in the walking simulation performed during imagery as they are comparatively faster in motor imagery than the normal controls, once the time taken to walk is subtracted; (3) the fMRI data on normal controls showed that motor imagery of walking in normal controls depends on a rich fronto-parietal pattern at the cortical level with stronger activation of cerebellar and brainstem gait specific regions for motor imagery rather than imitation through imagery task. (4) Finally patients with knee osteoarthritis displayed stronger fMRI activations in walking-specific brain regions for motor imagery, compared with normal controls, providing that the motor imagery task was performed in combination with an explicit simulation of gait through explicit ankle dorsiflexion. Taken together, these results (1) contribute to the definition of the normal brain patterns associated with simulated gait, (2) testify to a qualitatively different, yet still available, ability in representing a walking behavior through motor imagery in patients with knee osteoarthritis both at a behavioral and (3) at a functional anatomical level. With some additional care, like the combination of the execution of a minimal peripheral motor behavior (the ankle dorsiflexion), the present data provide a rationale to test the hypothesis that motor imagery may prove of some use in boosting motor recovery of walking in patients with knee osteoarthritis after surgery. This is something that I should be able to discuss in person when specific experiments on motor imagery in motor rehabilitation will be completed.

Dissertação para a obtenção do Grau de Mestre em Engenharia Biomédica
Human behaviour is grounded in our ability to perform complex tasks. While human motor function has been studied for over a century the cortical processes underlying motor behaviour are still under debate. Central to the execution of action is the primary motor cortex (M1), which has previously been considered to be responsible for the execution of movements planned in the premotor cortex, yet recent studies point to more complex roles for M1 in orchestrating motor-related information. The purpose of this project is to study the functional properties of primary motor cortex using ultra-high fMRI. The spatial resolution made possible by using a high field magnet allows us to investigate novel questions such as the existence of cortical columns, the functional organization pattern for single fingers and functional involvement of M1 in motor imagery and observation. Thirteen young healthy subjects participated in this study. Functional and anatomical high resolution images were acquired. Four functional scans were acquired for the different tasks: motor execution; motor imagery; movement observation and rest. The paradigm used was a randomized finger tapping. The images analysis was performed with the Brainvoyager QX program. Using the novel high resolution cortical grid sampling analysis tools, different cortical laminas of human M1 were examined. Our results reveal a distributed pattern (intermingled with somatotopic “hot spots”) for single fingers activity in M1. Furthermore we show novel evidence of columnar structures in M1 and show that non motor tasks such as motor imagery and action observation also activate this region. We conclude that the primary motor cortex has much more un-expected complex roles regarding the processing of movement related information, not only due to their involvement in tasks that do not imply muscle movement, but also due to their intriguing organization pattern.

Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction.   This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric ­– and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions.   The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions.    Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke.
Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke.   Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner.   Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen.   Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke.   Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.

Quel rôle joue la gravité dans les représentations internes de l'action ? Au-delà des contraintes d'équilibre, le vecteur gravitaire influence-t-il l'action de façon globale, jusqu'à la perception des mouvements de nos semblables ? Ces questions ont été celles qui ont guidé mes travaux de thèse. L'originalité de notre approche a été de placer l'exécution et la perception de l'action dans un « continuum fonctionnel » s'articulant autour des représentations internes de l'action. Pour ce faire, l'outil de choix qui est commun aux trois expériences de cette thèse est la microgravité (0G). Les expériences de cette thèse ont montré que les représentations internes de l'action se nourrissaient des informations graviceptives pour se construire et s'adapter constamment. Cependant, dans certaines conditions telle que la 0G à court terme, apparaît un ordre de priorité. En effet, le SNC est capable de mettre en place des solutions immédiates et efficaces pour l'exécution, comme en témoigne la repondération sensorielle rapide qui s'opère en 0G dans une tâche d'orientation posturale. Cependant, un temps de latence est observé dans la recalibration des modèles internes sur la base des afférences sensorielles fortement perturbées. C'est ce que nous avons montré grâce à un protocole d'imagerie motrice, mettant en évidence une perte de l'isochronie entre les mouvements exécutés et imaginés en 0G. Enfin, nous avons mis en évidence, chez des sujets sans expérience aucune de microgravité, que la perception du mouvement humain est efficace même lorsque ce dernier est exécuté en apesanteur, bien que des réseaux cérébraux différents soient mis en jeux
What is the role of gravity in the internal representations of action? Beyond the constraints of balance, does the gravity vector influence the action globally, up to the perception of our peers' movement? These issues have guided my thesis work. The originality of our approach was to place the execution and the perception of action in a "functional continuum" built around the internal representations of the action. To do this, the tool of choice, that is common to all three experiments presented here, is microgravity (0G). The experiments of this thesis showed that the internal representations of action are fed with graviceptive information to build and adapt constantly. However, under certain conditions such as short-term 0G, an order of priority appears. Indeed, the CNS is able to implement immediate and effective solutions, as we demonstrate it with the fast sensorial reweighting observed during a postural orientation task. However, a lag is observed in the recalibration of internal models based on sensory inputs severely disrupted. This is what we have shown through a protocol of motor imagery, showing a loss of isochrony between executed and imagined movements under 0G. Finally, we have demonstrated in subjects without any experience of microgravity, that the perception of human movement is effective even when it is performed in weightlessness, although different cerebral networks are involved

Ce travail de thèse repose sur la combinaison de deux paradigmes de recherche en psychologie cognitive : la rotation mentale et les transferts intermodaux/inter-tâches. Dans notre première étude (Expériences 1a, 1b, 1c, 2a, et 2b), l'objectif était d'évaluer la dépendance/indépendance des traitements visuel et tactile, lors de tâches de rotation mentale : le Test des Rotations Mentales (Vandenberg & Kuse, 1978) et une tâche élémentaire de rotation mentale (Shepard & Metzler, 1971). En utilisant un plan expérimental intra-sujet, nous avons comparé quatre conditions expérimentales incluant des apprentissages intramodaux : 1. Visuel-Visuel ; 2. Tactile-Tactile, et des transferts intermodaux : 3. Visuel-Tactile ; 4. Tactile-Visuel. Les participants ont ainsi réalisé deux tâches successives dans des conditions sensorielles similaires ou différentes (session 1 et session 2). Nos résultats révèlent que la rotation mentale peut dépendre de processus de traitement des représentations spécifiques à la modalité sensorielle utilisée. Les informations découlant d'une expérience visuelle sont réutilisables dans la condition tactile, alors qu'à l'inverse, nous n'avons observé que très peu de transferts tactiles en condition visuelle. Les traitements visuels et tactiles, sur des objets tridimensionnels complexes, permettent ainsi le développement de stratégies d'imagerie mentale spécifiques (Visuel-Visuel-IM vs. Tactile-Spatial-IM), découlant de différents modes de traitements perceptifs (visuel-global vs. tactile-spatial)
The work presented in this dissertation is based on the combination of two research paradigms in the field of cognitive psychology: mental rotation and intermodal/inter-task transfer of learning. In our first study (Experiments 1a, 1b, 1c, 2a, and 2b), the objective was to evaluate the processing dependence/independence of visual and tactile information during two mental rotation tasks: the Mental Rotation Test (Vandenberg & Kuse, 1978) and an object mental rotation task (Shepard & Metzler, 1971). Using an intra-subject experimental design, we compared four experimental conditions including intramodal learning: 1. Visual-Visual ; 2. Tactile-Tactile, and intermodal transfer: 3. Visual-Tactile ; 4. Tactile-Visual. Subjects performed two successive tasks in similar perceptual conditions or different perceptual conditions (session 1 and session 2). Our results revealed that mental rotation can depend on treatment processes of mental representations specific to the perceptual modality being used. The information derived from visual prior experience can be used in the tactile condition, whereas we observed few significant tactile transfers in the visual condition. Visual and tactile treatments on complex three-dimensional objects thus permit specific mental imagery strategies (Visual-Visual-IM vs. Tactile-Spatial-IM), derived from different perceptual exploration strategies (visual-global vs. tactile-spatial)

Trabalho de Projeto do Mestrado Integrado em Engenharia Biomédica apresentado à Faculdade de Ciências e Tecnologia
A técnica de imagem usando ressonância magnética funcional (IRMf) é uma abordagemeficaz para medir a função cerebral, uma vez que pode medir o sinal dependente do nível de oxigéniono sangue (BOLD), uma medida indireta da atividade neural. Recentes avanços permitiram odesenvolvimento de IRMf em tempo real (rt-fMRI), em que o sinal BOLD de uma (ou mais regiões)está disponível em tempo real. Neurofeedback (NF) é um tipo de biofeedback em que umarepresentação visual, auditiva ou outra de natureza cognitiva, da atividade cerebral medida (regiãoespecífica de interesse - ROI - ou correlação de dois substratos neurais de uma rede funcional) éapresentada ao participante para facilitar a auto-regulação desses correlatos neurais. Há evidênciascrescentes de que há mudanças patológicas na interação entre regiões cerebrais associadas adistúrbios psiquiátricos e neurológicos. Uma experiência rt-fMRI-NF pode permitir a manipulação nainteração funcional entre regiões, representando assim uma maneira de estudar a relação entrecomportamento e auto-regulação de medidas de conectividade. NF baseado em conectividade foipreviamente sugerido como uma abordagem promissora, possivelmente fornecendo um melhorindicador de um aumento na dificuldade da tarefa, bem como uma ferramenta valiosa para melhorara aprendizagem e neuroreabilitação. Este projeto visa projetar e testar um protocolo que permita aosparticipantes auto-regular a conectividade funcional em tempo real, calculada com uma Correlaçãode Pearson com janelas deslizantes, entre regiões que se sobrepõem durante performance motora(MP) e imaginação motora (MI), como o córtex premotor bilateral (PMC). Para este fim, osparticipantes são encorajados a adaptar tarefas de imaginação motora. A nossa hipótese é baseadana noção de que controlo de aprendizagem sobre substratos neuronais específicos (ou interaçõesentre regiões), modifica comportamentos específicos, função cerebral e neuro plasticidade, podendorepresentar uma estratégia terapêutica para distúrbios relacionados à conectividade. Os resultadosmostram que os participantes foram capazes de modular conectividade inter-hemisférica obtendorepresentação visual do valor de correlação entre PMC bilateral como neurofeedback em tempo real.Isto suporta a ideia de que é possível criar uma aplicação terapêutica de treino motor em indivíduoscom diminuição da conectividade inter-hemisférica, como doentes com que sofreram de AVC.
Functional magnetic resonance imaging technique (fMRI) is an effective approach to measurebrain function since it can measure blood oxygenation level-dependent (BOLD) signal, an indirectmeasure of neural activity. Recent advances allowed the development of real-time fMRI (rt-fMRI), inwhich the BOLD signal of one (or more regions) is available in real-time. Neurofeedback (NF) is a typeof biofeedback in which a visual, auditory or cognitive representation of the measured neural activity(specific region of interest - ROI - or correlation of two neural substrates of a functional network ispresented to the participant to facilitate self-regulation of the neural correlates. There is increasingevidence that there are pathological disturbances in the functional interaction between brain regionsassociated to psychiatric and neurological disorders. A Real-time Functional Magnetic ResonanceImaging Neurofeedback (rt-fMRI-NF) experiment might enable the manipulation of interactionsbetween regions, and thus represents a way of investigating the relationship between behavior andself-regulation of connectivity measures. Connectivity-based NF has previously been confirmed as asuitable approach for neurofeedback implementation and possibly a valuable tool to enhance motorlearning and rehabilitation. This project aims to design and test a framework that enables theparticipants to self-regulate the functional connectivity, calculated with a windowed PearsonCorrelation, between regions that overlap during motor performance (MP) and motor imagery (MI)such as bilateral premotor cortex (PMC) in real time. To this end, participants are encouraged to usea adaptive motor imagery task. Our hypothesis is based on the notion of learning control over specificneural substrates (or interactions between regions) changes specific behaviors, brain function andneuroplasticity, and may represent a therapeutic strategy for connectivity-related disorders. The resultsshow that the participants were able to modulate interhemispheric connectivity while getting visualrepresentation of the value of correlation between bilateral PMC as real-time neurofeedback. Thissupports the idea that it is possible the design a motor training as a therapeutical application in subjectswith decreased interhemispheric connectivity such as stroke patients.