A case of developmental deep dyslexia: what's left is right.

Cases of acquired deep dyslexia have not clearly and consistently supported any of the theoretical models. We report on a case of a 51-year-old right-handed female, L.S., with a developmental history of deep dyslexia in order to test the neuropsychological models using a visual half-field semantic priming paradigm. Word targets were primed either by a highly associated word (e.g., CLEAN-DIRTY), a weakly associated word (e.g., CLEAN-TIDY), or an unrelated word (e.g., CLEAN-FAMILY) projected to either the same or opposite visual field (VF) as the target. In normals, RVF-left hemisphere primes result in high associate priming regardless of target location (ipsilateral or contralateral to the prime), whereas LVF-right hemisphere primes produce both high and low associate priming across both target location conditions (Hutchinson, Whitman, Abeare & Raiter, 2003). In contrast, L.S. showed hyperpriming to both high and low associates only in the left hemisphere with inhibition of high associates in the right hemisphere. This case represents a variation of developmental deep dyslexia in which the patient's left hemisphere functions like a normal right hemisphere. However, the lack of exclusively high associate priming in the opposite (right) hemisphere may not provide the necessary narrowing of semantic activation necessary for normal reading and thus, may lead to semantic reading errors. Theoretical implications are discussed.