tailieunhanh - Independent component analysis P22

Brain Imaging Applications With the advent of new anatomical and functional brain imaging methods, it is now possible to collect vast amounts of data from the living human brain. It has thus become very important to extract the essential features from the data to allow an easier representation or interpretation of their properties. This is a very promising area of application for independent component analysis (ICA). Not only is this an area of rapid growth and great importance; some kinds of brain imaging data also seem to be quite well described by the ICA model. This is especially the case with. | Independent Component Analysis. Aapo Hyvarinen Juha Karhunen Erkki Oja Copyright 2001 John Wiley Sons Inc. ISBNs 0-471-40540-X Hardback 0-471-22131-7 Electronic 22 Brain Imaging Applications With the advent of new anatomical and functional brain imaging methods it is now possible to collect vast amounts of data from the living human brain. It has thus become very important to extract the essential features from the data to allow an easier representation or interpretation of their properties. This is a very promising area of application for independent component analysis ICA . Not only is this an area of rapid growth and great importance some kinds of brain imaging data also seem to be quite well described by the ICA model. This is especially the case with electroencephalograms EEG and magnetoencephalograms MEG which are recordings of electric and magnetic fields of signals emerging from neural currents within the brain. In this chapter we review some of these brain imaging applications concentrating on EEG and MEG. ELECTRO- AND MAGNETOENCEPHALOGRAPHY Classes of brain imaging techniques Several anatomical and functional imaging methods have been developed to study the living human brain noninvasively that is without any surgical procedures. One class of methods gives anatomical structural images of the brain with a high spatial resolution and include computerized X-ray tomography CT and magnetic resonance imaging MRI . Another class of methods gives functional information on which parts of the brain are activated at a given time. Such brain imaging methods can help in answering the question What parts of the brain are needed for a given task 407 408 BRAIN IMAGING APPLICATIONS Well-known functional brain mapping methods include positron emission tomography PET and functional MRI fMRI which are based on probing the changes in metabolic activity. The time resolution of PET and fMRI is limited due to the slowness of the metabolic response in the brain which