Quantification of corpus callosum myelination was estimated from MOG immunofluorescence detected with a Spot 2 CCD camera. Using Metamorph software, pixel intensity values were normalized between sections by thresholding to exclude values below the level of immunoreactivity in the dorsal fornix, which was selected as an adjacent white matter tract that is not demyelinated by cuprizone. The percent area of the corpus callosum (midline bilaterally to a point under the cingulum apex) with MOG immunoreactivity above the threshold level was then used as an estimate of the myelinated area.