Poster D87, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Exemplar repetition at encoding alters the specificity of retrieval-related mnemonic information
Erik Wing1, Wei-Chun Wang1, Mark Hatcher1, Roberto Cabeza1; 1Duke University
Episodic memories may vary along many dimensions, including the degree of detail or specificity pertaining to an initially experienced event. Previous work has shown that encoding a number of related or overlapping concepts can produce an overall conceptual gist, even as individual items become harder to distinguish in memory. The present study examined how the repetition of similar items during initial encoding might lead to a loss of specificity in mnemonic representations when the corresponding concepts were later retrieved. Subjects initially viewed a series of object pictures in an incidental categorization task. While some object concepts appeared only once, for others, six similar exemplar pictures were shown in separate runs across the encoding session. Unsurprisingly, a word memory test administered one day later showed better memory for concepts in the exemplar repeat condition. While successful retrieval of previously repeated vs. single concepts was associated with increased activity in left ventrolateral prefrontal cortex (VLPFC), measures of encoding-retrieval similarity (ERS) showed a different effect. In both frontal and occipitotemporal cortex, correspondence with encoding patterns was higher during the retrieval of words that had been initially shown in picture form only once vs. those associated with multiple picture exemplars. This dissociation suggests a reduction in representational specificity of gist-based memories that may be characterized by the reinstatement of primarily conceptual vs. exemplar-specific information.
Topic Area: LONG-TERM MEMORY: Episodic