Dysgraphia in dementia: a systematic investigation of graphemic buffer features in a case series.

In this paper we report findings from a systematic investigation of spelling performance in three patients - PR, RH and AC - who despite their different medical diagnoses showed a very consistent pattern of dysgraphia, more typical of graphemic buffer disorder. Systematic investigation of the features characteristic of this disorder in Study 1 confirmed the presence of length effects in spelling, classic errors (i.e., letter substitution, omission, addition, transposition), a bow-shaped curve in the serial position of errors and consistency in substitution of consonants and vowels. However, in addition to this clear pattern of graphemic buffer impairment, evidence of regularity effects and phonologically plausible errors in spelling raised questions about the integrity of the lexical spelling route in each case. A second study was conducted, using a word and non-word immediate delay copy task, in an attempt to minimise the influence of orthographic representations on written output. Persistence of graphemic buffer errors would suggest an additional, independent source of damage. Two patients, PR and AC, took part and in both cases symptoms of graphemic buffer disorder persisted. Together, these findings suggest that damage to the graphemic buffer may be more common than currently suggested in the literature.