Εξόρυξη γνώσης από μαγνοτοεγκεφαλογραφικά δεδομένα μελέτη του οφθαλμολογικού συστήματος
Magnetoencephalographic research on oculomotor system
Τσιρούκη, Ανθή Κωνσταντίνου
A lot of studies have been developed that concern the relation between cerebral activity and the oculomotor system. In the present research the exact role of cortical areas in the posterior parietal cortex (PPC) in the eye movement and specifically in the saccadic movements is analyzed. A main issue that was studied, above many other, and concerns the cortical activation is that the eye movement processes involves the distance of the fixation target. The problem outgrows if we regard that there are two types of saccades, voluntary and reflexive. In our experiment voluntary saccadic movements were studied. In order to accomplice this 10 right - handed healthy volunteers, approved from the French national committee for human research (CCPPRB, Pitiι-Salpκtriθre Hospital), perform a modified memory-delay task.The experimental task was executed two times. In the first task participants were near the screen, while in second far. Eye movements were recorded binocularly with EOG. MEG activity was recorded with a whole head MEG system (151 sensors, CTF Canada). The anatomical MRI scan was acquired for each subject in the study. Data from the three basic periods of task were statistically studied: a) shift of attention to the target, b) target memorization, c) saccade initiation to the target.To reach to useful conclusions the multitude of cortical signals underwent sophisticated signal analysis that aimed at organizing the information in a compact form and presenting it in a directly interpretable way. Every subject’s signals were clustered using the prototyping method of Neural Gas network. In this way the different activation waveforms were compared across all cortical areas. Using Mountain-clustering algorithm the responses from different subjects were checked for consistencies and possible outliers. Finally, a differential curve was created, for each brain region, based on a class-discriminability index that helped us to compare brain responses from different recording conditions. From analyzing the whole set of available data (different conditions/tasks/subjects), we mined the useful information and presented in a table that can help the neuroscientist to scan the differentially activated brain regions, at specific response latencies, and hopefully will assist him in understanding the dynamics of occulomotor system.
Έχουνε γίνει πολλές έρευνες με αντικείμενο τη συσχέτιση της εγκεφαλικής λειτουργίας με το οφθαλμοκινητικό σύστημα. Στη συγκεκριμένη έρευνα μελετήθηκε ο ακριβής ρόλος των περιοχών που βρίσκονται στο posterior parietal cortex (PPC) στην κίνηση των ματιών και συγκεκριμένα στις σακκαδικές κινήσεις. Ένα από τα βασικότερα θέματα που μελετήθηκε αφορά στην εγκεφαλική δραστηριότητα όταν στις διαδικασίες κίνησης των ματιών εμπλέκεται και η μετατόπισης των αντικειμένων εστίασης στο χώρο. Το πρόβλημα γίνεται μεγαλύτερο αν λάβουμε υπ’ όψιν μας ότι υπάρχουν δύο ειδών σακκαδικές, οι εκούσιες και οι αντανακλαστικές.
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