Selective alexia and agraphia sparing numbers-a case study.
We report a patient (MT) with a highly specific alexia affecting the identification of letters and words but not numbers. He shows a corresponding deficit in writing: his letter writing is impaired while number writing and written calculation is spared. He has no aphasia, no visuo-perceptual or -constructional difficulties, or other cognitive deficits. A similar pattern of performance has to our knowledge only been reported once before [Anderson, S. W., Damasio, A. R., & Damasio, H. (1990). Troubled letters but not numbers. Domain specific cognitive impairments following focal damage in frontal cortex. Brain, 113, 749-766]. This study shows that letter and number reading are dependent on dissociable processes. More interestingly, it points to a common mechanism subserving the perception and production of letters. We suggest that a deficit in a visuo-motor network containing knowledge of the physical shape of letters might explain the pattern of performance displayed by MT.
Starrfelt
Randi
R
Department of Psychology, University of Copenhagen, Linnésgade 22, DK-1361, Copenhagen, Denmark. randi.starrfelt@psy.ku.dk
D000293:Adolescent; D001921:Brain / Q000503:physiopathology; D001924:Brain Concussion / Q000503:physiopathology*; D004411:Dyslexia, Acquired / Q000209:etiology* / Q000503:physiopathology*; D016489:Head Injuries, Closed / Q000503:physiopathology*; D006801:Humans; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed