Localisation of brain functions : stimuling brain activity and sourcereconstruction for classification/
Year: 2006
Type: dissertation
Abstract: A key issue in understanding how the brain functions is the ability to\ncorrelate functional information with anatomical localisation.\nFunctional information can be provided by a variety of techniques like\npositron emission tomography (PET), functional MRI (fMRI),\nelectroencephalography (EEG), magnetoencephalography (MEG) or\ntranscranial magnetic stimulation (TMS). All these methods provide\ndifferent, but complementary, information about the functional areas of\nthe brain. PET and fMRI provide spatially accurate picture of brain\nregions involved in a given task. TMS permits to infer the contribution\nof the stimulated brain area to the task under investigation. EEG and\nMEG, which reflects brain activity directly, have temporal accuracy of\nthe order of a millisecond. TMS, EEG and MEG are offset by their low\nspatial resolution. In this thesis, we propose two methods to improve\nthe spatial accuracy of method based on TMS and EEG.\nThe first part of this thesis presents an automatic method to improve\nthe localisation of TMS points. The method enables real-time\nvisualisation and registration of TMS evoked responses and MRI. A MF\ndigitiser is used to sample approximately 200 points on the subject's\nhead following a specific digitisation pattern. Registration is obtained\nby minimising the RMS point to surface distance, computed efficiently\nusing the Euclidean distance transform. Functional maps are created from\nTMS evoked responses projected onto the brain surface previously\nsegmented from MRI.\nThe second part presents the possibilities to set up a brain-computer\ninterface (BCI) based on reconstructed sources of EEG activity and the\nparameters to adjust. Reconstructed sources could improve the EEG\nspatial accuracy as well as add biophysical information on the origin of\nthe signal. Both informations could improve the BCI classification step.\nEight BCIs are built to enable comparison between electrode-based and\nreconstructed source-based BCIs. Tests on detection of laterality of\nupcoming hand movement demonstrate the interest of reconstructed\nsources.
Author: Quentin Noirhomme
Institution: University of Liège
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2168342059