Phonological Dyslexia: Loss of a Reading-specific Component of the Cognitive Architecture?

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Abstract
In phonological dyslexia, nonword reading is impaired while the reading of both regular and irregular words is preserved. Many phonological dyslexics are able to repeat the same nonwords that they are unable to read. This constellation of abilities and deficits has been interpreted as the result of impairment in the ability to translate orthography to phonology, as distinct from the impairment of orthography or phonology themselves. If this interpretation is correct, then the brain must contain some tissue that is dedicated to this reading-specific ability, that is, tissue which is necessary for this and only this ability. This, in turn, implies that school-age learning can determine the existence and nature of anatomically separate (hence selectively lesionable) neural systems. Our interest in this issue has led us to consider an alternative explanation of phonological dyslexia, according to which it results from a general (i.e. not reading-specific) impairment of phonological representation. We explain how a patient with apparently good nonword repetition might nevertheless have a general impairment of phonological representation that affects nonword reading, and we test this explanation with one such patient. We also discuss the evidence for and against this hypothesis available in other published cases of dissociated nonword reading and repetition.