Writing without Graphic Motor Patterns: A Case of Dysgraphia for Letters and Digits Sparing Shorthand Writing

Abstract

This paper reports the case of a patient HP who presents a dysgraphia affecting the production of letters and digits while sparing shorthand writing. HP's writing impairmentis two-fold. On one hand, HP produces systematic lettersubstitutions affecting exclusively lower-case letters b, p, d, and q. Such confusions are also observed in tasks assessing the mental imagery of letters and the processing of visually presented, isolated letters. This deficit is attributed to a circumscribed disruption of allographic representations. On the other hand, HP can write correctly formed letters and digits but the production of these symbols is slow and nonfluent. This disturbance was investigated by using a digitising tablet to record movements performed in grapho-motor production. The results of the analysis of temporal and kinematic indices suggest that graphic motor patterns of letters and digits are no longer available to this patient, whereas motor patterns underlying the production of shorthand seem unaffected. Itis suggested thatthere are two ways forproducing spatially well-formed symbols. One route is mediated by graphic motor patterns and the other by a motor planning system that would be used in other tasks involving the generation of 2D trajectories as in drawing or in tracing unfamiliar symbols.