Weddell R A, Davidoff J B
Department of Surgical Neurology, Morriston Hospital, Swansea, United Kingdom.
Brain Cogn. 1991 Nov;17(2):240-71. doi: 10.1016/0278-2626(91)90076-k.
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.
