Authors:

PATTERSON, K. & Macdonald, M.C.

Reference:

Year of publication:

2006

CBU number:

6147

Abstract:

Neuropsychological studies constitute one way of addressing the issue of the independence/interdependence of various components of language processing. The focus of this chapter is the content and structure of speech in patients with semantic dementia (SD) - a progressive brain disease involving relatively selective disruption to semantic knowledge. Descriptions of SD speech available in the literature, which are mainly anecdotal, suggest that it is abnormal only in lexical/semantic content and unaffected in both phonological and syntactic structure. The adequacy of this description was assessed in the current study by analyses of short spoken narratives, produced to describe a pictured scene, from 21 SD patients and 21 age-matched normal speakers. As expected, the SD patients' narratives, relative to those of the normal speakers, were dramatically reduced in lexical/semantic content. What the patients did produce was (a) completely normal in terms of the phonological structure of individual words, but (b) not normal in syntactic structure. Although frank grammatical errors were rare, the structure of the SD narratives was substantially simplified. Of particular note, the patients produced significantly fewer noun phrases following verbs than the normal speakers, and often used pronouns such as it or she without clear referents. The chapter concludes with some discussion as to why impoverished lexical availability might be expected to affect syntax but not phonology.