Discourse processing in women with fragile x syndrome: evidence for a deficit establishing coherence.

The language phenotype in individuals with fragile X syndrome (FXS) and its relation to the molecular genetics of the disorder was investigated. Previous research has focused on describing deviance in conversational speech, and has not yet examined component discourse skills. The ability of women with FXS to use coherence to select endings to humorous and straightforward passages was evaluated, and the relation of this with neuropsychological measures of working memory, executive functions, and molecular measures of the syndrome were also evaluated. Three groups of nonretarded women were examined: (a) 14 women with FXS who carry the full mutation; (b) 25 women who carry the premutation; and (c) 16 women without the fragile X mutation. The results indicated that subjects with the full mutation showed a dramatic deficit in selecting appropriate endings to jokes relative to stories, even though the jokes were identical to the stories except for their endings. The coherence deficit found in the jokes task for women with the full mutation was found to correlate strongly with the X activation ratio, and to a neuropsychological measure of working memory. The full mutation subjects' coherence deficit is discussed in terms of the additional demand to hold information in memory and shift set.