Phonological Alexia

The defining feature of phonological alexia is a strong familiarity effect (i.e., a marked deficit in reading pseudowords) in the face of a relatively intact ability to read real words. Although this may seem to have little relevance for reading in the real world (we are rarely called on to read pseudowords), in fact patients with phonological alexia do complain of difficulty reading, although their complaints are often nonspecific.

Some patients with phonological alexia also have difficulty reading functor words (prepositions, conjunctions, etc.) and may have a tendency to delete, add, or substitute affixes (e.g., read faded as "fade" or "fading").

An explanation of phonological alexia that accounts for both the primary difficulty reading pseudowords and the secondary difficulty reading functors is that it represents a disturbance in connections between written words (orthography) and their pronunciation (phonology), forcing reading to proceed via direct connection between orthography and meaning (semantics). Most functors and affixes serve primarily a syntactic role and have weak representations within the semantic network. Pseudowords, of course, have no semantic value and thus cannot be read via meaning.

The errors that these patients produce when attempting to read pseudowords often seem to be derived from the target word in some way. Commonly, the initial phoneme (sound) is correct. Often, a word that is orthographically similar to the target word is produced. Some very short pseudowords may be read entirely correctly; long pseudowords are rarely read correctly.

The reading of patients with phonological alexia does not exhibit a regularity effect. If a length effect is seen, it is dependent on the number of syllables or phonologic complexity, not the number of letters. A part-of-speech effect may be seen, particularly for functors, as noted previously. A concreteness effect is occasionally seen in phonological alexia. Patients with phonological alexia do not always display the analogous deficit in writing (phonological agraphia).

The lesion causing phonological alexia is quite variable but is normally located within the distribution of the left middle cerebral artery.

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