Falsecolour nuclear magnetic resonance NMR image of a midsagittal section through a human head showing structures of a normal brain airways facial tissues The heavilyfolded cerebral cortex the grey matter which forms the outer part of the cerebrum appears green yellow red Beneath it at right appears the feathery outline of the cerebellum Immediately to the left of the cerebellum in red are the structures of the brainstem an enlarged extension of the spinal cord The uppermost bones of the neck are seen to the left of the spinal cord The airway of the throat cerebrospinal fluid surrounding the brain spinal cord appear dark blue