BrainFacts.org (SfN)

Ask a Neuroscientist: Sarah Heilbronner

Dr. Sarah Heilbronner outlines how magnetic resonance imaging, the workhorse of modern neuroscience, can be tuned to reveal three distinct layers of brain information. Structural MRI produces high‑resolution maps of gray‑matter regions, white‑matter tracts, ventricles, and the brain’s relationship to the skull, highlighting individual anatomical variability. Functional MRI captures moment‑to‑moment neuronal activation by having subjects perform tasks—such as solving a crossword puzzle—while the scanner records localized blood‑oxygen changes that “light up” engaged regions. Diffusion‑weighted MRI leverages the random motion of water molecules; in tightly packed axon bundles, diffusion is constrained, allowing researchers to infer the orientation of fiber pathways and approximate the brain’s wiring diagram. These techniques together provide the only non‑invasive window into the living human connectome, informing both basic research and clinical diagnostics.