During the last decade, a number of remarkable magnetic resonance imaging (MRI) techniques have been developed for measuring human brain activity and structure. These MRI techniques have been accompanied by the development of signal processing, statistical and visualization methodologies. We review several examples of these methods, drawn mainly from work on the human visual pathways. We provide examples of how two methods- functional MRI (fMRI) and diffusion tensor imaging (DTI) - are used. First, we explain how fMRI enables us to identify and measure several distinct visual field maps and measure how these maps reorganize following disease or injury. Second we explain how DTI enables us to visualize neural structures within the brain's wires (white matter) and measure the patterns of connectivity in individual brains. Throughout, we identify signal processing, statistical, and visualization topics in need of further methodological development.