These observations led us to propose that in AD, the primary pathology results in a secondary retrograde atrophy of cholinergic neurons of the nucleus basalis (Cuello and Sofroniew, 1984) which could be rescued by the application of exogenous mature NGF (mNGF), including the compensatory de novo cholinergic synaptogenesis of the remaining, non-lesioned, cortical tissue. This evidence concerns the gene NGF and Alzheimer disease.