Lexical-semantic retention and speech production:further evidence from normal and brain-damaged participants for a phrasal scope of planning.

The present study investigated the scope of planning in speech production by examining onset latencies for sentences describing moving picture displays. The experimental sentences began with either a simple or complex noun phrase, but were matched in length and content words. Results from young and old normal participants replicated previous findings of Smith and Wheeldon (1999) in showing longer onset latencies for sentences beginning with a complex noun phrase, supporting a phrasal scope of planning. Two aphasic patients were tested who, in previous studies, had shown a short-term memory deficit either in semantic retention (patient ML)or in phonological retention (patient EA). Patient ML showed a markedly greater disadvantage for the sentences beginning with a complex noun phrase whereas EAshowed an effect within normal range. The present results from the patients, together with those from previous studies, indicate that the phrasal planning is occurring at a lexical-semantic level using a capacity that is also involved in comprehension.