LEXICAL AND SEMANTIC BINDING EFFECTS IN SHORT-TERM-MEMORY - EVIDENCE FROM SEMANTIC DEMENTIA

Two case studies are presented of the short-term memory performance of patients with semantic dementia. The first case showed a pervasive pa ttern of semantic effects in his auditory verbal short-term memory per formance, in particular a marked superiority in serial recall for sequ ences of ''known'' words over ''unknown'' words-words which he no long er comprehended. His performance in serial recall tasks was characteri sed by abundant phonemic errors, which occurred with a frequency shown to be related to semantic factors. These errors were often migrations of phonemes from one word in the List to another, suggesting that imp aired semantic processing reduces the ''glue'' or ''binding'' that hel ps to maintain a structured sequence of phonemes in short-term memory. The second patient also showed some semantic effects in serial recall : and a significant but less marked pattern of phonological errors. Th e differing performance of the two patients is interpreted within an i nteractive activation model of word production (Saffran & Martin, 1990 ; Martin, Saffran, & Dell, 1996).