'Letter-by-letter' reading: recognition, recovery and rehabilitation

Objectives: There is now a relatively large body of literature focusing on the form of acquired dyslexia known as letter-by-letter reading, pure alexia or alexia without agraphia. The hallmark of this disorder is a length effect in reading aloud This paper addresses two other pertinent issues: 'covert' reading ability and recovery and rehabilitation of the impairment. Methods: This paper presents a single case study of a 47 year old man, BL, with a left occipita-temporal CVA It documents detailed assessment of the nature of his disorder over time, and his rehabilitation. Results: BL is demonstrated to have extremely poor word reading with a characteristic effect of number of letters on performance, and poor single letter identification However he shows some preserved 'covert" knowledge of words he is unable to read aloud: he performs better than chance at lexical decision and provide semantic information for words that he is unable to read aloud. Moreover, unlike previous cases in the literature this 'covert' recognition, is NOT dependant on brief presentation of the stimulus BL's word reading was treated using two tasks: lexical decision and auditory-visual word pairing The effects of each of these tasks on reading and recognition of treated and untreated words were documented. Conclusions: The implications of the data from BL for theoretical accounts (including the 'right hemisphere' account and the 'visual processing' impairment account) of pure alexia will be discussed.