Short-term retention of lexical-semantic representations: Implications forspeech production

Patients with semantic STM deficits have difficulty comprehending sentences that require the retention of several lexical-semantic representations pri or to their integration into higher-level propositions (Martin, 1995; Marti n & Romani, 1994). In Experiment 1, patients with a semantic retention defi cit had difficulty with the same type of constructions in speech production , namely noun phrases with one or two pre-nominal adjectives. Their perform ance improved when they could produce the nouns and adjectives in sentence form, which placed smaller demands on lexical-semantic retention. In Experi ment 2 these patients were better able to produce syntactically complex sen tences than the pre-nominal adjective phrases having an equal number of con tent words, indicating that the findings in Experiment 1 could not be attri buted to syntactic complexity. These patients produced more pauses in the s entence constructions in Experiments 1 and 2, suggesting that the timing of such productions is abnormal. In contrast, patient EA, with a phonological retention deficit, performed better than the patients with a semantic rete ntion deficit on the AN phrases despite having a smaller STM span. She show ed no significant benefit of producing sentence compared to phrase construc tions, and also made fewer and shorter pauses than the other patients. Thes e findings support the multiple capacities view of verbal working memory an d suggest that the same semantic retention capacity used in language compre hension is used in speech production.