A dyscalculic patient with selectively impaired processing of the numbers 7, 9, and 0.

A patient (J.C) had particular difficulties with the numbers 7, 9, and 0 in aurally and visually presented calculations. These problems were explained in terms of a modified version of the McCloskey, Caramazza, & Basili (1985) model of calculation processes. His calculation difficulties were attributed to degraded semantic representations of the numbers 7 and 9 and to lost knowledge of rules governing calculations involving the number 0. Use of "noncalculation" number processing tasks confirmed that his 7/9 problem was not at the level of acoustic analysis, the auditory input lexicon, the phonological output lexicon, visual analysis, or the orthographic output lexicon.