7 research outputs found
Development of an algorithm that identifies the optimum final point of the stimulation electrode for deep brain stimulation, using the beta frequency band of intranuclear recordings
No full text88 σ.Αντικείμενο της παρούσας διπλωματικής εργασίας αποτελεί η δημιουργία ενός αλγορίθμου που υποστηρίζει την ταυτοποίηση της βέλτιστης τελικής θέσης του ηλεκτροδίου της εν τω βάθει εγκεφαλικής διέγερσης σε ασθενείς με τη νόσο του Parkinson. Σύμφωνα με πρόσφατη έρευνα στο εργαστήριο Βιοϊατρικών Προσομοιώσεων και Απεικονιστικής Τεχνολογίας του Εθνικού Μετσόβιου Πολυτεχνείου υπάρχουν ενδείξεις ότι η πυροδότηση στη β – ζώνη συνδέεται με αντίστοιχη αύξηση της ενέργειας στη β – ζώνη στα δυναμικά τοπικού πεδίου που λαμβάνονται από ενδοπυρηνικές καταγραφές μικροηλεκτροδίων εντός της αισθητικοκινητικής περιοχής του υποθαλαμικού πυρήνα. Η παρούσα διπλωματική εργασία διευρύνει τη μελέτη της σχέσης μεταξύ της αύξησης της ενέργειας στη β – ζώνη και των κλινικών αποτελεσμάτων της χειρουργικής διαδικασίας.
Οι ενδοπυρηνικές καταγραφές μικροηλεκτροδίων προέρχονται από 18 ασθενείς της Νευροχειρουργικής Κλινικής του Νοσοκομείου Ευαγγελισμός.
Η υπόθεση μας περί βελτίωσης των κλινικών κινητικών συμπτωμάτων όταν στην περιοχή όπου εφαρμόζεται η εν τω βάθει διέγερση έχει παρατηρηθεί η ύπαρξη μέγιστης κορύφωσης πλάτους της καταγραφής στη β – ζώνη συχνοτήτων υποστηρίζεται από τα αποτελέσματά μας. Στην περιοχή όπου εφαρμόζεται η εν τω βάθει διέγερση, 62.5% των ασθενών με καλή κλινική απόκριση εμφάνισαν μία μέγιστη κορύφωση πλάτους της καταγραφής στη β – ζώνη, ενώ 63.2% των ασθενών με κακή κλινική απόκριση δεν εμφάνισαν αντίστοιχη μέγιστη κορύφωση.The present thesis introduces an algorithm that supports the identification of the optimum final point of the stimulation electrode for the Deep Brain Stimulation (DBS) on Parkinson’s patients. A recent study at the Biomedical Simulations and Imaging (BIOSIM) Laboratory of the National Technical University of Athens shows evidence of the existence of correlations between beta band firing of the neurons and the increase of beta band energy in local field potentials acquired during intranuclear microelectrode recordings in the sensorimotor area of the subthalamic nucleus. The present study further expands the correlation study between this increase in beta band energy and the clinical outcome of DBS.
The intranuclear microelectrode recordings were acquired by 18 Parkinson’s patients from the Neurosurgery Clinic of Evangelismos Hospital.
Our hypothesis that the existence of a maximum beta band amplitude peak in the DBS area is related to an amelioration of clinical motor-related symptoms was supported by our results. More specifically, 62.5% of the patients with a good clinical response had a beta band amplitude peak in the DBS area, whereas 63.2% of the patients with poor clinical response didn’t have a beta band amplitude peak in the DBS area.Πολυτίμη Δ. Φράγγο
Cultural Differences in Visual Perceptual Learning
No full textCultural differences in visual perceptual learning (VPL) could be attributed to differences in the way that people from individualistic and collectivistic cultures preferentially attend to local objects (analytic) or global contexts (holistic). Indeed, individuals from different cultural backgrounds can adopt distinct processing styles and learn to differentially construct meaning from the environment. Therefore, the present work investigates if cross-cultural differences in VPL can vary as a function of holistic processing. A shape discrimination task was used to investigate whether the individualistic versus collectivistic backgrounds of individuals affected the detection of global shapes embedded in cluttered backgrounds. Seventy-seven participants – including Asian (collectivistic background) and European (individualistic background) students – were trained to discriminate between radial and concentric patterns. Singelis' (1994) self-construal scale was also used to assess whether differences in learning could be attributed to independent or interdependent self-construal. Results showed that collectivists had faster learning rates and better accuracy performance than individualists following training – thereby reflecting their tendency to attend holistically when learning to extract global forms. Further, we observed a negative association between independent self-construal – which has previously been linked to analytic processing – with performance. This study provides insight into how socio-cultural backgrounds affect VPL
Microstructural and neurochemical plasticity mechanisms interact to enhance human perceptual decision-making.
No full textExperience and training are known to boost our skills and mold the brain's organization and function. Yet, structural plasticity and functional neurotransmission are typically studied at different scales (large-scale networks, local circuits), limiting our understanding of the adaptive interactions that support learning of complex cognitive skills in the adult brain. Here, we employ multimodal brain imaging to investigate the link between microstructural (myelination) and neurochemical (GABAergic) plasticity for decision-making. We test (in males, due to potential confounding menstrual cycle effects on GABA measurements in females) for changes in MRI-measured myelin, GABA, and functional connectivity before versus after training on a perceptual decision task that involves identifying targets in clutter. We demonstrate that training alters subcortical (pulvinar, hippocampus) myelination and its functional connectivity to visual cortex and relates to decreased visual cortex GABAergic inhibition. Modeling interactions between MRI measures of myelin, GABA, and functional connectivity indicates that pulvinar myelin plasticity interacts-through thalamocortical connectivity-with GABAergic inhibition in visual cortex to support learning. Our findings propose a dynamic interplay of adaptive microstructural and neurochemical plasticity in subcortico-cortical circuits that supports learning for optimized decision-making in the adult human brain
Neurogenetic phenotypes of learning-dependent plasticity for improved perceptual decisions
No full textGenetics and experience are known to mold our cognitive development. Yet, the interactions between genetics and brain mechanisms that support learning and flexible behavior in the adult human brain remain largely unknown. Here, we test the link between brain-wide gene expression and macroscopic neuroimaging phenotypes of brain plasticity that support our ability to improve perceptual decisions with training. We demonstrate that gene expression links to learning-dependent changes in spatial variations of cortical microstructure and functional connectivity in visual and fronto-parietal networks that are known to be involved in perceptual decisions. Further, we show that brain stimulation in visual cortex during training boosts learning and alters functional connections, rather than microstructure organization, within and between these networks. Our results reveal neurogenetic phenotypes of plasticity in perceptual decision networks, providing insights into the interplay of genetic expression and macroscopic mechanisms of structural and functional plasticity for learning and flexible behavior
Neurochemical and functional interactions for improved perceptual decisions through training
No full textLearning and experience are known to improve our ability to make perceptual decisions. Yet, our understanding of the brain mechanisms that support improved perceptual decisions through training remains limited. Here, we test the neurochemical and functional interactions that support learning for perceptual decisions in the context of an orientation identification task. Using magnetic resonance spectroscopy (MRS), we measure neurotransmitters (i.e., glutamate, GABA) that are known to be involved in visual processing and learning in sensory [early visual cortex (EV)] and decision-related [dorsolateral prefrontal cortex (DLPFC)] brain regions. Using resting-state functional magnetic resonance imaging (rs-fMRI), we test for functional interactions between these regions that relate to decision processes. We demonstrate that training improves perceptual judgments (i.e., orientation identification), as indicated by faster rates of evidence accumulation after training. These learning-dependent changes in decision processes relate to lower EV glutamate levels and EV-DLPFC connectivity, suggesting that glutamatergic excitation and functional interactions between visual and dorsolateral prefrontal cortex facilitate perceptual decisions. Further, anodal transcranial direct current stimulation (tDCS) in EV impairs learning, suggesting a direct link between visual cortex excitation and perceptual decisions. Our findings advance our understanding of the role of learning in perceptual decision making, suggesting that glutamatergic excitation for efficient sensory processing and functional interactions between sensory and decision-related regions support improved perceptual decisions
Delopment and Validation of the Transcranial Magnetic Stimulation Reporting Assessment Tool (TMS-RAT)
No full textThis place is the storage for all supplementary materials associated with our manuscript 'Development and Validation of the Transcranial Magnetic Stimulation Reporting Assessment Tool (TMS-RAT)'
