Consequences of Reduced Representational Distinctiveness and of Temporal Instability on Reading Accuracy in Patients with Dysgraphia due to Orthographic Short-term Memory Damage: A New Case and a Literature Review

摘要

Orthographic Working Memory (OWM) maintains graphemic strings active until the correspondingwords/pseudowords are spelled. OWM damage yields segmental spelling errors on long stimuli,without lexical-semantic effects. In subjects with OWM damage, errors follow a bow-shaped or alinear-increase distribution. These contrasting patterns have been attributed to loss of distinctproperties of orthographic representations in OWM. Reduced distinctiveness of elements in therepresentation mostly affects graphemes in central positions (hence, the bow-shaped distribution),and temporal instability of the orthographic string affects graphemes in proportion to distance fromthe word’s beginning (hence, the linear error increase) (Costa et al., 2012).It has been proposed that the same OWM system is involved not only in word/pseudoword spelling,but also in reading pseudowords - but not words (Caramazza et al., 1996). This is becausepseudoword reading, just like word/pseudoword spelling, requires an orthographic string to remainactive while further processing stages are completed. In available reports, however, pseudowordreading accuracy is comparable to word reading in some cases, and disproportionately impaired inothers. This leads to ask whether a shared OWM system, or distinct input (for reading) and output(for spelling) OWM systems better account for the data.