A peripheral reading deficit under conditions of diffuse visual attention.
Humphreys GW., Mayall K.
We report a single case study of a patient, FL, who has a peripheral dyslexia with symptoms resembling attentional dyslexia. FL demonstrated impaired identification of letters within strings, and better identification of words than their constituent letters. We found that FL was impaired at both letter counting and same-case letter matching with letter strings, and his matching and naming performance were strongly affected by letter spacing. The effects of these visual variables on performance suggest an early locus to FL's deficit. We propose that letter identification was disrupted by abnormal lateral masking and poor location coding within words. These peripheral processing deficits were reduced when the task required focused attention on the central letter location. Nevertheless, even with impaired letter coding, word representations could be accessed to some degree, via supra-letter units. We discuss the implications of the data for understanding normal reading.