Multimodal Neuroimaging to Visualize Human Visual Processing
Each non-invasive neuroimaging modality has its own inherent limitations resulting from temporal and special inaccuracies due to the nature of information that can be measured. While functional magnetic resonance imaging (fMRI) techniques provide excellent spatial resolution, (up to sub-millimeter resolution), their temporal resolution is limited by the hemodynamic time constant. Conversely, magnetoencephalography (MEG) and electroencephalography (EEG), which measure temporal changes in neural current directly, have temporal resolution of approximately a few milliseconds. However, their spatial accuracy is limited by the non-unique nature of the problem of estimating the spatial distribution of neural currents from the measurement of voltage (EEG) or magnetic field (MEG) distributions from outside of the brain. In this chapter, recent developments in multimodal neuroimaging are introduced to allow for the reconstruction of human brain dynamics with high spatial accuracy without compromising temporal resolution. Specifically, the author describes a technique to combine data from MEG, MRI, and fMRI to visualize human visual processing while perceiving a three-dimensional (3-D) shape.