[Writing, aging and Alzheimer's disease].

Writing is a complex and fragile cognitive function, that appeared very late in the history of mankind, and that also develops quite late in individuals. Aging does not induce changes in the lexical, semantic and syntaxic parameters of the writing description of a complex image. In the same way, spelling is not significantly altered through aging. Spelling errors are rare among seniors: they only concern infrequent words and mostly respect their pronunciation. The most frequent errors are about accents or double letters. Margins get smaller, seniors raise their pens less often and the pressure and width of writing decrease with age. Writing get progressively disorganized during Alzheimer's disease. The content of texts is primarily affected, texts becoming shorter and less coherent. Then, spelling is altered by regularization errors which are an evidence of lexical agraphia. Then, lexical agraphia gets worse and rapidly becomes mixed, combining lexical and phonological features. Finally, dementia worsens along with a massive deterioration of graphic features and spatial organization. Agraphia of Alzheimer's disease comes from a progressive and hierarchized disorganization of the various components of language and writing, due to the brain lesions in several associative areas, i.e. the parietal, temporal, occipital and frontal regions.