The Japanese journal of neuropsychology

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ArticleTitle	Number processing disorder following left parieto-temporal infarction in an ambidextrous patient
Language	J
AuthorList	Norio Suzuki¹⁾, Minoru Matsuda²⁾, Yasuhiro Nagahama²⁾, Tomoko Okina³⁾
Affiliation	1) Department of Speech Therapy, Shiga Prefectural Medical Center 2) Department of Geriatric Neurology, Shiga Prefectural Medical Center 3) Department of Psychology, Shiga Prefectural Medical Center
Publication	Japanese Journal of Neuropsychology: 21 (1), 49-57, 2005
Received	Feb 10, 2004
Accepted	Sep 21, 2004
Abstract	We reported on a case of the serious disorder of number processing caused by an infarction in the left parieto-temporal lobe. The subject was a 68 year-old ambidextrous woman experiencing a number processing disorder and aphasia. The aphasia gradually improved, but the number processing disorder persisted. Number processing ability was examined when the subject had recovered to a level where a perfect score was achieved on the language tests that examined the auditory understanding of words except numbers, and reading ability of Kana and Kanji words. She could neither understand verbally presented one-digit numerals nor accurately respond orally to the number of dots presented. She also experienced difficulty in visually perceiving one-digit Arabic numerals and performed poorly on the task requiring her to select dots corresponding with an Arabic numeral. She could not write Arabic numerals. Furthermore, she had difficulty in reading Arabic numerals aloud and misread the digits of the numerals. Thus, severe difficulties were observed in understanding/utterance of numerals and reading/writing of Arabic numerals. In addition, it was difficult for her to deal with numbers themselves, evident through poor performances of tasks such as comparing and matching numbers of dots. This fact suggests a degradation and narrowing of the number concept. Without their identifiable symbol, numbers themselves are abstract concepts. Hence, if this symbolic numerical form is absent, number concepts may become unstable. The degradation in the subject's number concepts may be caused by the loss of ability to perceive symbolic representations of both auditory and visual codes of numbers. It is possible that the severe difficulty in recognizing the symbolic form of a number is attributable to her abnormal functional lateralization. Numbers are normally understood via both right and left hemispheres of the brain, but in her case, the representation of Arabic numerals may be unilaterally restricted to her left hemisphere.
Keywords	acalculia, number processing, arabic numerals, conception of number, ambidextrality