Magnetic resonance imaging (MRI) is a common diagnostic tool used in medicine, but MRI techniques can also be used to map the direction of water movement within tissues. Such a technique is called diffusion tensor imaging (DTI), and researchers have used DTI to study the 3D structure of the brain. Seen here are axons from neurons in a monkey brain with different directionality: red means the axon travels left to right, green front to back, and blue top to bottom. This image was collected to understand how cocaine use causes long-term changes in the brain’s structure and connectivity.
Image by John D. Olson, Paul W. Czoty, and Michelle Bell, Wake Forest University School of Medicine.