| Summary: | Thesis (Ph.D.)--Boston University === This thesis explored multimodal brain imaging using advanced
spatiotemporal techniques. The first set of experiments were based on
simulations. Much controversy exists in the literature regarding the differences
between magnetoencephalography (MEG) and electroencephalography (EEG},
both practically and theoretically. The differences were explored using
simulations that evaluated the expected signal-to-noise ratios from reasonable brain sources. MEG and EEG were found to be complementary, with each
modality optimally suited to image activity from different areas of the cortical
surface. Consequently, evaluations of epileptic patients and general
neuroscience experiments will both benefit from simultaneously collected
MEG/EEG. The second set of experiments represent an example of MEG
combined with magnetic resonance imaging (MRI) and functional MRI (fMRI)
applied to healthy subjects. The study set out to resolve two questions relating to
shape perception. First, does the brain activate functional areas sequentially
during shape perception, as has been suggested in recent literature? Second,
which , if any, functional areas are active time-locked with reaction-time? The
study found that functional areas are non-sequentially activated, and that area IT
is active time-locked with reaction-time. These two points, coupled with the
method for multimodal integration , can help further develop our understanding of
shape perception in particular, and cortical dynamics in general for healthy
subjects. Broadly, these two studies represent practical guidelines for epilepsy
evaluations and brain mapping studies. For epilepsy studies, clinicians could
combine MEG and EEG to maximize the probability of finding the source of
seizures. For brain mapping in general, EEG, MEG, MRI and fMRI can be
combined in the methods outlined here to obtain more sophisticated views of
cortical dynamics.
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