Surface dyslexia in nonfluent progressive aphasia.
This article presents the case of a 59-year-old male, JH, with a 6-year history of primary progressive aphasia (PPA), a disorder characterized by isolated language deterioration with relative preservation of other cognitive abilities. JH also shows typical features of surface dyslexia, a reading disorder exemplified by the selective preservation of phonological reading. One recent theory is that surface dyslexia in individuals with PPA results from a loss of semantic knowledge. In this paper we consider an additional possibility and present data supporting the notion that surface dyslexia may also arise from the malfunction in the links between semantic representations and phonology. JH has remarkably preserved lexical semantic knowledge when assessed on tasks that do not require verbal output. Further, item-by-item comparisons of his oral reading and comprehension ability show no significant correspondence between his reading and semantic knowledge. These findings lead us to conclude that, in JH's case, the surface dyslexia is attributable not to a semantic deficit per se but rather to the inability to access phonological information from semantics. JH's language profile is considered in relation to potential sources of surface dyslexia and other cases of progressive aphasia.
Watt
S
S
Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto, Canada. swatt@io.org
Jokel
R
R
Behrmann
M
M
D001039:Aphasia, Broca / Q000150:complications* / Q000503:physiopathology; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology; D004410:Dyslexia / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D011386:Projective Techniques; D015899:Tomography, Emission-Computed, Single-Photon