Poster A73, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Prototype representations in ventromedial prefrontal cortex and hippocampus during concept generalization
Caitlin Bowman1, Dagmar Zeithamova1; 1University of Oregon
Healthy memory function involves both the ability to remember specific details of prior events and the ability to integrate common event features to form abstract concepts that guide behavior in new situations. The nature of the memory representations supporting these two functions has been of considerable debate. Prototype models posit that abstract representations of central tendency are formed to guide generalization. Exemplar models posit that abstract information can be extracted on demand from individual instances and does not need to be maintained as a distinct representation. The present study used a category-learning task to simultaneously measure event-specific and abstract representations. Participants were trained to sort exemplars into two categories, then underwent functional MRI 1) while passively viewing training items and new exemplars and 2) during a generalization test that probed for category knowledge applied to novel exemplars. Exemplar and prototype models were fit to behavioral data in individual subjects and then used as regressors in neuroimaging data to identify the neural correlates of each. Behavior was better fit by the prototype than the exemplar model, associated with robust prototype correlates in the ventromedial prefrontal cortex and anterior hippocampus during the generalization test. In contrast, during passive viewing of old and new exemplars, neural pattern similarity analyses revealed that posterior hippocampus and portions of parietal cortex were sensitive to event-specific information. Together, results show that event-specific and abstract representations co-exist within the hippocampus and that medial prefrontal and parietal regions differentially support these representations to serve multiple memory functions.
Topic Area: LONG-TERM MEMORY: Episodic