The concept of structure, operation, and functionality, as they may be
understood by clinicians or researchers using neural transplantation
techniques, are briefly defined. Following Stein & Glasier, we emphasi
ze that the question of whether an intracerebral graft is really funct
ional should be addressed not only in terms of what such a graft does
in a given brain structure, but also in terms of what it does at the l
evel of the organism.