Abstract
Although amnesic H.M. typically could not recall where or when he met someone, he could recall their topics of conversation after long interference-filled delays, suggesting impaired encoding for some categories of novel events but not others. Similarly, H.M. successfully encoded into internal representations (sentence plans) some novel linguistic structures but not others in the present language production studies. For example, on the Test of Language Competence (TLC), H.M. produced uncorrected errors when encoding a wide range of novel linguistic structures, e.g., violating reliably more gender constraints than memory-normal controls when encoding referent-noun, pronoun-antecedent, and referent-pronoun anaphora, as when he erroneously and without correction used the gender-inappropriate pronoun “her” to refer to a man. In contrast, H.M. never violated corresponding referent-gender constraints for proper names, suggesting that his mechanisms for encoding proper name gender-agreement were intact. However, H.M. produced no more dysfluencies, off-topic comments, false starts, neologisms, or word and phonological sequencing errors than controls on the TLC. Present results suggest that: (a) frontal mechanisms for retrieving and sequencing word, phrase, and phonological categories are intact in H.M., unlike in category-specific aphasia; (b) encoding mechanisms in the hippocampal region are category-specific rather than item-specific, applying to, e.g., proper names rather than words; (c) H.M.’s category-specific mechanisms for encoding referents into words, phrases, and propositions are impaired, with the exception of referent gender, person, and number for encoding proper names; and (d) H.M. overuses his intact proper name encoding mechanisms to compensate for his impaired mechanisms for encoding other functionally equivalent linguistic information.
Highlights
Amnesic H.M. typically could not recall where or when he met someone, he could recall their topics of conversation after long interference-filled delays, suggesting impaired encoding for some categories of novel events but not others
Per Test of Language Competence (TLC) response, H.M. violated reliably more gender, person, and number conjunction constraints (CCs) than the controls for the common noun antecedents of pronouns and for the referents of pronouns and common nouns, and he omitted reliably more common nouns, determiners, and modifiers than the controls when forming common noun noun phrases (NPs). These results indicate that H.M. can conjoin referents with proper names of the appropriate person, number, and gender without difficulty, but he produces encoding errors when conjoining referents and common noun antecedents with pronouns of the appropriate person, number, and gender, and when conjoining referents with common nouns of the appropriate person and gender
This contrast between H.M.’s encoding of proper names versus pronouns and common nouns comports with the working hypothesis outlined earlier: Under this hypothesis, H.M. overused proper names relative to memory-normal controls when referring to people in MacKay et al [2] because (a) his mechanisms are intact for conjoining the gender, number, and person of an unfamiliar person with proper names, unlike his corresponding mechanisms for pronouns, common nouns, and NPs with common noun heads, and (b) H.M. used his impaired encoding mechanisms for proper names to compensate for his impaired encoding mechanisms for the only other ways of referring to people: pronouns, common nouns, and common noun NPs
Summary
Amnesic H.M. typically could not recall where or when he met someone, he could recall their topics of conversation after long interference-filled delays, suggesting impaired encoding for some categories of novel events but not others. To illustrate (a) the usefulness of Lashley’s strategy for providing insights into amnesia, and (b) some background questions that motivated the present research, consider the following excerpt from H.M.’s conversational speech at age 44 in the 182-page transcript of Marslen-Wilson [5]. To illustrate these background questions, we have divided this brief excerpt into four segments
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