[Two-way deficit between phonological and arabic representation of numbers after left parieto-occipital hemorrhage]

A 52-year-old right-handed man developed a deficit of two-way transcoding between phonological and Arabic representations of numbers after cerebral hemorrhage in the left occipital lobe, intraparietal sulcus, and the surrounding of inferior parietal lobule. He showed right hemianopia, mild Wernicke's aphasia, agraphia, and phonological dyslexia. Calculation, comparison between numbers and comprehension of arithmetic signs were almost preserved. Retrieval of the mnemonic rhymes for the multiplication table (kuku) was moderately compromised. He showed good performance in the following tasks: selecting coins corresponding to the number orally designated by the experimenter, reporting orally the amount of arranged coins, selecting coins according to written amount, indicating the amount of arranged coins by writing numbers, and choosing the amount of arranged coins from several alternatives of written numbers. Thus, encoding the phonological and visual representations of numbers from the meanings as well as decoding from these 2 representations into their meanings were preserved. However, he showed grave difficulty in dictation of numbers, in choosing the verbally indicated numbers from among a set of written numbers, and in reading aloud a number. Thus, two-way impairment of association between phonological and visual representations of numbers was confirmed. Regarding other categories of nouns, marked deterioration was detected only in dictation and writing the names of indicated objects. We taught him a strategy of imaging the coins when he transcoded from Arabic representation of numbers to phonological representation and vice versa. This strategy improved his performance to some extent. These results suggest that there is a direct, bi-directional transcoding route between phonological and visual representations of numbers, which is not mediated by semantic representation. This route can be impaired by a lesion located in the left parieto-occipital cortex.