Atypical semantic knowledge and autobiographical memory disorder in a young adult with Downs syndrome

A study of lexical semantic knowledge and autobiographical memory is described in PQ, a 22-year-old male with Downs syndrome. Performance is compared with younger typically developing verbal mental age controls. PQ's lexical stores contained a normal number of items, however, he was impaired at naming both pictures and item descriptions. PQ's own descriptions of items contained a normal volume of information, but the pattern of information differed from normal as he produced less 'sensory' and more 'thematic' and 'functional' information. PQ has an autobiographical memory deficit. His ability to recall 'specific' memories was significantly impoverished. It is suggested that both PQ's naming difficulties and his autobiographical memory disorder may reflect atypical knowledge specification with absence of distinctive featural knowledge and increased conceptual overlap and looser networks pervasive across both semantic and autobiographical memory systems.