Assessing recollection and familiarity of similar lures in a behavioral pattern separation task

The relationship between recollection-mediated recognition memory and behavioral pattern separation is poorly understood. In two separate experiments, we modified a well-validated object discrimination task with previously demonstrated sensitivity to neural pattern separation with instructions to assess recollection and familiarity. In the first experiment, we included a Remember/Know (R/K) judgment, and in the second we included a source memory judgment. We found that both Remember and correct source judgments were higher for lures labeled similar (where pattern separation is engaged) but also higher on lures called old (where pattern separation is absent), suggesting that false alarms in pattern separation tasks are frequently mediated by recollection. As one might expect, Remember judgments and correct source decisions increased with greater dissimilarity for similar responses and increased with greater similarity for old responses. This suggests that recollection can occur in the presence and in the absence of pattern separation and that false alarms to similar lures are not simply driven by familiarity. (c) 2013 Wiley Periodicals, Inc.