One of the fundamental principles of brain organization is functional specialization within anatomically distinct regions. However, normal and abnormal information processing in the brain occurs across several time scales. Basic and clinical researchers therefore seek insight into both the distribution and the temporal orchestration of human brain regions involved in a given behavioral or cognitive task. The overall goal of this research is to provide an integrated neuroimaging method for mapping the spatiotemporal dynamics of human brain function. The proposed model for this study will be the human visual system. The integration of the spatial and temporal domains represents a unique challenge because of the existence of distinct processing regions in the visual system which communicate across several time scales. The applicants presented an integrated methodology for spatiotemporal imaging that uses functional and anatomical MRI to inform and constrain the EEG/MEG forward/inverse problem, thereby improving the accuracy of neural activity maps of the visual system. The proposed experiments are designed to demonstrate the efficacy of the integrated fMRI/EEG/MEG technique and to provide further insight into visual processing by the human brain. The applicants proposed to combine modeling studies with analysis of empirical data to use anatomical and functional MRI information to constrain the EEG/MEG forward/inverse solution. The modeling component (Aim 1) includes (i) Monte Carlo studies (ii) error analyses of model mis-specifications; and (iii) determination of optimal anatomical and functional MRI weightings. The analysis portion includes important developments of single-trial event-related paradigms for fMRI experiments. A series of fMRI and EEG/MEG studies of the human visual system will then be performed, using paradigms that permit systematic variation in the intensity and location of the source distribution, ranging from simple to complex visual stimuli. The ability to manipulate the activity will offer a basis of evaluation for the fMRI/EEG/MEG technique versus direct intracranial measurements. This research will enable mapping of the human brain with the spatial resolution of fMRI and the temporal resolution of EEG/MEG.
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