Pure misallocation of "0" in number transcoding: A new symptom of right cerebral dysfunction

To account for the mechanism of number transcoding, many authors have proposed various models, for example, semantic-abstract model, lexical-semantic model, triple-code model, and so on. However, almost all of them are based on the symptoms of patients with left cerebral damage. Previously, I reported two Japanese patients with right posterior cerebral infarction showing pure misallocation of '' 0 '' (omission: '' 40265 '' '' 4265 '', addition: '' 107 '' -> '' 1007 '', transposition: '' 4072 '' -> '' 4702 '') both in writing and oral reading of Arabic numerals. To examine whether the pure misallocation of '' 0 '' is commonly observed in patients with right cerebral damage, I investigated writing and oral reading of Arabic numerals in 18 patients with right cerebral damage and 16 healthy controls. All patients with right cerebral damage showed pure misallocation of '' 0 '' both in writing and reading. The pure misallocation of '' 0 '' due to right cerebral damage cannot be explained by current models. It may be more useful to explain the phenomenon by regarding an Arabic numeral as graph on a two-dimensional plane composed of two axes (place-holding values and digits). (c) 2005 Elsevier Inc. All rights reserved.