The model of a central language system comprises three components: phonology (speech sound production), lexicon (vocabulary), and syntax (sentence construction). Within the secondary language system of writing, an additional phoneme-to-grapheme conversion system is necessary, triggering the motor patterns for letters and an orthographic system.
While strings of letters are generated via the phonological route, entire words are produced via the semantic route. Various readers may rely more or less on one or the other, but usually they work in parallel fashion (the dual-
Figure 1. Handwriting of a 66-year-old right-handed man who had suffered a left temporal cerebral hematoma one month previously, developing transcortical-sensory aphasia. On dictation ("Wohin wird sie es mir bringen?" [Where is she going to take it for me?]) he wrote: "wi nin gricht es sich," producing literal (first three words) and verbal (last word) paragraphias.
route hypothesis). They may, however, be impaired selectively, yielding to different agraphia types.
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