A virtual brain MRI shown in the three standard planes: axial, sagittal and coronal. Drag a slider to move through the brain, or click inside any image to aim the other two views at that spot. Switch the scan contrast or color the tissue types to see where gray matter and white matter sit. On a T1 scan, gray matter is the darker tissue and white matter the brighter one. Then pick a diagnosis to see the structural differences large MRI studies report, and what happens after treatment.
Can MRI diagnose it?
See the same diagnosis at the level of chemistry in Synapse to Symptom, and as brain activity (fMRI, PET, EEG) in Scanning the Mind.
Model % shows how far this teaching model shifts each structure, exaggerated so the change is visible. Real group differences are much smaller; the right-hand column gives the published effect size (Cohen's d).
Gray matter holds neuron cell bodies, dendrites and synapses, where information is processed. It forms the 2–4 mm outer cortex and the deep nuclei (thalamus, caudate, putamen, hippocampus, amygdala).
White matter is bundles of axons wrapped in fatty myelin, the wiring between regions. The fat makes it look white in a real brain and bright on T1 MRI.
CSF (cerebrospinal fluid) fills the ventricles and the grooves (sulci) between folds. Gray and white matter each make up roughly 40–50% of adult brain volume.
| Scan | White | Gray | CSF |
|---|
T1 is the anatomy scan: white matter bright, CSF dark. T2 reverses that, so fluid and swelling glow. FLAIR is a T2 scan with the fluid signal cancelled, which makes lesions next to the ventricles (such as MS plaques) stand out.
Mental-health research measures gray matter volume and cortical thickness from T1 scans, and white-matter tracts with DTI.
Six questions on Slice by Slice. Rate how sure you are for each one. Your answers are anonymous and add to the class results. Or practice with a timed game, alone or with classmates.