Orthographic Representations and Working Memory Properties in the Spelling Process: A Neuropsychological Analysis

The present thesis investigates the graphemic stage of the spelling process. Aim of thesis is to study the sub-processes occurring at the orthographic working memory level and the interaction between graphemic representations and working memory that holds these representations active during spelling. Chapter 1, after a brief description of the two-routes spelling model adopted in this research, deals with, presenting neuropsychological evidences, some of the most important issues about the relations between the different levels of elaboration that are engaged in the spelling process. Final part of this chapter is dedicated to the review of the neuropsychological researches regarding the structural organization and the processing of the orthographic representation. Chapter 2 reports the cases of GSI and CRI, two dysgraphic subjects with a selective deficit for consonants and a graphemic buffer disorder (GBD), whose spelling patterns are consistent with the hypothesis that their deficits affect different properties of orthographic working memory: temporal stability for GSI and representational distinctiveness for CRI. Their performance on spelling task demonstrate two things: first, GBD is not a homogeneous deficit because different sub-processes, involved in graphemic buffering, can be selectively affected by cerebral damage; second, different patterns of GSI and CRI arise from interaction of consonant representation and WM properties, both impaired in these subjects. Chapter 3 reports the case of a third dysgraphic subject, PPO, with a selective disorder for consonants but whose spelling picture was not identifiable as a clear GBD. Spelling pattern of this subject, quite different from those of both subjects of Chapter 2, demonstrates that the internal structure of orthographic representation, holding at working memory level, can be selectively impaired in the absence of working memory deficit. Moreover, PPO’s results on spelling task confirm the role of temporal stability and representational distinctiveness in the spelling and the interaction between representations and WM. Finally, Chapter 4 summarizes all the presented results and discusses the implications