Does dyslexia develop from learning the alphabet in the wrong hemisphere? A cognitive neuroscience analysis

A new perspective is described which views developmental dyslexia as the outcome of learning to write the alphabet in the nondominant (right) hemisphere. The letter-level and whole-word subtypes of dyslexia are seen as differing responses adopted to cope with this predicament. Striking similarities between dyslexics and callosotomy patients in the allocation of covert attention to lateralized stimuli provide direction for integrating a diversity of dyslexic research within this framework. This synthesis, together with information from pure alexia, brain activation, and reading research, lends insight into the neural circuitry of the compensatory strategies adopted by the two dyslexic subtypes.     

Age-of-acquisition effects in pure alexia

Pure alexia is an acquired reading disorder in which previously literate adults adopt a letter-by-letter processing strategy. Though these individuals display impaired reading, research shows that they are still able to use certain lexical information in order to facilitate visual word processing. The current experiment investigates the role that a word's age of acquisition (AoA) plays in the reading processes of an individual with pure alexia (G.J.) when other lexical variables have been controlled. Results from a sentence reading task in which eye movement patterns were recorded indicated that G.J. shows a strong effect of AoA, where late-acquired words are more difficult to process than early-acquired words. Furthermore, it was observed that the AoA effect is much greater for G.J. than for age-matched control participants. This indicates that patients with pure alexia rely heavily on intact top-down information, supporting the interactive activation model of reading.