Afferent dysgraphia and the role of vision in handwriting

Afferent dysgraphia is an acquired writing deficit characterized by deletions and duplications of letters and strokes. The commonly accepted interpretation is that patients do not use visual and kinaesthetic input. In this paper, we describe a woman who, following right brain damage, made errors almost exclusively involving letters with repeated strokes. She was normal at a kinaesthetic recognition task and, like the control subjects, produced more errors when blindfolded. We conclude that afferent dysgraphia does not result neither from an impairment of vision and kinaesthesis, or from an attentional deficit. Rather, it results from a defective mechanism, specific to handwriting, which computes afferent information to keep track of position in letter and stroke sequences.