A galactolipid that is an important component of the normal turnover of myelin in nerve fibers. When there is an enzyme deficiency, excess galactosylceramide and psychosine (both galactolipids) store in certain cells- forming the globoid cells seen in Krabbe disease and the consequential damage found in myelin-forming cells. This damage leads to demyelination in the nervous system, the predominant clinical feature of Krabbe disease.