A case for case: handling letter case selection in written spelling.

This study reports the unusual writing performance of a 72-year-old woman, Pp, who was unable to maintain her writing within a particular case, and made numerous case mixing errors (e.g. insTEAd). Her oral spelling was flawless, but when tested using a written spelling task (including words and non-words), a picture description task, a sentence writing task and a transcription task (from upper case to lower case, and vice versa), she showed a high proportion of case mixing errors, though spelling per se was correct. The problem, although less severe, was also present when spelling with letter cards. Despite a spared ability to select the correct letters in the stimulus, specify the correct number of letters and place them in the correct order, she had a specific problem in selecting the appropriate case. This impairment is indicative of peripheral dysgraphia. She appeared to have intact orthographic representations, but selection of the appropriate allographic codes for upper and lower case was impaired. Her longitudinal neuropsychological profile and MRI evidence suggest that Pp suffers from mild vascular dementia with more severe impairments in attentional functions. Her writing deficits may be accounted for by a model that incorporates an inhibitory mechanism, which is responsible for maintaining the appropriate case and inhibiting the inappropriate one, subsequent to case selection in writing. Failure of this mechanism would explain the pattern of case mixing shown by Pp.