Authors:

PATTERSON, K.

Reference:

Year of publication:

2000

CBU number:

4020

Abstract:

Knowledge of word meanings (semantics) is clearly central to the abilities to produce and comprehend connected speech; but most theories of languageprocessing assume that word meaning is not significantly implicated in single-word tasks such as reading aloud, writing to dictation, or morphological transformations like generating the past tense of a verb from its present-tense form. The "triangle" model of lexical processing, on the other hand, includes the premise that semantic representations of words interact with phonological and orthographic representatons in all forms of lexical processing. It further predicts that, because the non-semantic networks underlying these tasks capture both generalisable and word-specific knowledge of the relationships between different modalities or forms of a given word, the interaction with semantic knowledge should have a somewhat more influential role for lower-frequency words with an unpredictable relationship between orthography and phonology (in reading and spelling) or the two tenses (in past-tense transformations). This paper reviews results from these three tasks for patients with semantic dementia, who have a relatively selective and progressive disorder of semantic knowledge. The accuracy, nature of errors, and other features of their performance provide consistent support for the predictions of the triangle model concerning the impact of sematic impairment on these 'non-semantic' language abilities.