Abstract
Magnetic resonance imaging (MRI) can be used to map the pattern of diffusion in tissue. These diffusion MR measurements allow us to infer the complex pattern of long-range anatomical connections in the human brain. Understanding these connections and measuring their properties in individual brains is important because they are crucial to normal brain function, their disruption may underlie many neurological disorders, and their variability across individuals may explain behavioral variability. These connections also mature relatively late in development and limit neural plasticity in the adult. In the visual system, we can routinely find and measure the connections between the retina and the LGN (the optic nerve and optic tract), the connections from the LGN to V1 (the optic radiation), and many cortical connections important in visual processing. I will discuss diffusion MR measurements that we and others have made in the visual system and describe how these measures advance our understanding of the visual processing circuits. Finally, I will describe our efforts to more precisely measure neural tissue properties by using quantitative tissue models to combine diffusion measures with other quantitative MR measures such as longitudinal relaxation and magnetization transfer.