The simultaneous activation hypothesis: explaining recovery from deep to phonological dyslexia

Deep dyslexia evolved into phonological dyslexia in one patient. Semantic errors resolved while phonological and derivational errors persisted in reading. Nonword reading improved but remained inferior to word reading. Despite a residual semantic deficit naming improved. The Simultaneous Activation Hypothesis explains recovery from deep to phonological dyslexia and the continued dissociation between reading and naming errors. Partial recovery to all three reading routes increased constraints for word selection at the phonological output lexicon (POL) improving word reading. With recovery, the POL receives additional supportive information from the partially recovered direct oral reading route and grapheme-to-phoneme conversion (GPC) eliminating semantic errors in oral reading. Nonword reading also improved because of partial recovery to all three routes. Semantic errors in naming persisted because additional constraints were unavailable at the POL to activate a phonological entry. Phonological and derivational errors were more frequent in reading than in naming the result of incomplete GPC recovery. Residual nonword reading deficits resulted from incomplete GPC recovery, indicated by the persistence of neologisms in nonwords. The Simultaneous Activation Hypothesis readily accounts for the evolution from deep to phonological dyslexia.