IMPAIRED ENCODING OF ABSTRACT LETTER ORDER: SEVERE ALEXIA IN A MILDLY APHASIC PATIENT

Abstract

We describe the single word reading impairment of a patient with severe acquired alexia in the context of largely spared auditory-verbal language. DES shows strong effects of lexical variables when reading words; she is completely unable to read nonwords. Her “visual” reading errors (orthographically related word substitutions) reflect a strong positional bias to differ from targets toward their right sides; this positional bias was evident across several different topographic transformations of the stimuli and was present in her spelling errors. Such a pattern of positional letter retention is commonly associated with right “neglect dyslexia” and has been interpreted as indicating damage to a spatially encoded word representation. However, DES shows no sign of spatial impairment in nonlanguage tasks, fails to demonstrate several of the characteristics thought to be diagnostic of “neglect dyslexia,” and shows no evidence of neglect in sentence reading. In contrast to the spatial account, we interpret DES's primary impairment as one involving a prelexical, transient level of representation in which letter order is coded abstractly (i.e. neither spatially nor serially).