HM's language production deficits: Implications for relations between memory, semantic binding, and the hippocampal system

To test the claim that H.M. exhibits a "pure memory deficit" that has left his language production intact, we compared the language production of H.M. and controls in three studies. In Study 1. participants described the two meanings of visually presented sentences that they knew were ambiguous, and H.M.'s descriptions suggested a semantic-level production deficit: Relative to controls of comparable age, intelligence, and education, H.M.'s descriptions were significantly less effective, less clear, less concise. and more repetitious at lexical, phrase. and sentence levels of language production. In Study 2, naive judges rated H.M.'s descriptions as less grammatical, less comprehensible, and less coherent than descriptions of controls. Study 3 replicated these results for conversational speech about childhood events that occurred ion before H.M.'s operation. his epilepsy, and his epilepsy treatments. Present results contradict stages of processing theories that localize H.M.'s deficit to a storage stage that is independent of processes for retrieving and producing verbal materials, and instead support a distributed-memory theory in which memory storage and retrieval involving verbal materials are inherent aspects of normal language production. (C) 1998 Academic Press.