Après un bref rappel de l’historique des études de l’expression écrite dans la maladie d’Alzheimer (MA), les auteurs font une revue des travaux d’inspiration cognitive consacrés aux processus centraux et périphériques. L’évaluation des processus centraux dans les études de groupes et dans les études de cas multiples montre une atteinte prédominante de la composante lexicale de l’écriture. Elle est révélée par la production d’erreurs phonologiquement plausibles sur les mots non transparents sur le plan des règles de correspondance phonème-graphème (mots irréguliers par exemple) et traduit une atteinte des représentations orthographiques des mots. L’atteinte périphérique a été beaucoup moins recherchée. Les études incluant une grande cohorte de patients rapportent que le stade allographique est affecté de façon plus importante que l’étape des programmes moteurs graphiques. Les études de cas multiples rendent compte de façon plus précise de l’atteinte de chacun des composants : lexical, phonologique, mémoire tampon graphémique, étape allographique, programmes moteurs graphiques mais aussi souligne la fréquence des atteintes conjointes. La dernière partie traite de méthodologie et expose un protocole d’évaluation.
Deficit of spelling and writing in Alzheimer’s diseaseThe authors first present a brief recall of the evolution of research on writing and spelling in Alzheimer’s disease (AD). Then, they make a review of cognitive works devoted to the central and peripheral processes. Regarding central processes, studies of AD patients have often highlighted a pattern of lexical agraphia, characterized by a regularity effect and the production of phonologically plausible errors. In other words, compared with controls, patients make more errors on irregular words or orthographically ambiguous words than on regular words or nonwords. This indicates that orthographic representations are lost or not accessible. The large predominance of the lexical deficit over the phonological processes and the graphemic buffer has been observed in group studies as in multiple single case studies. Peripheral aspects of writing have been investigated less thoroughly, even though typical peripheral errors as case errors and graphic errors have been mentioned in early reports. Studies which used specific tasks specially designed to distinguish between impairments at the level of allographic processing and at the level of the graphic motor pattern (such as writing to dictation, copying, cross-case transcription of lower- and upper-case letters and, more rarely, mental imagery) showed that allographic deficit is much important than alteration of the graphic motor patterns. The multiple single case studies which offer the possibility to delineate a specific profile of disturbance for each patient revealed that the typical lexico-semantic impairment can be observed in association with other central or peripheral disturbances. They reported a wide variety of agraphia syndromes, including a far from negligible number of patients with selective damage to one of the central or peripheral components, as well as patients with multiple writing impairments. One must therefore bear in mind that although lexical impairment is the most frequent pattern, it is not the sole deficit, either during the course of the disease or at its onset. So the hypothetical profile of agraphia in AD, evolving from lexical impairment towards other central and peripheral deficits remains plausible but the number of cases with a different pattern of deterioration in spelling and writing skills is far from negligible. In the last part, methodological aspects are exposed: interpretation of scores and errors and proposition of a protocol aimed to the evaluation of central and peripheral components of agraphia.
