Differential contributions of prefrontal, medial temporal, and sensory-perceptual regions to true and false memory formation.

The neural correlates of true memory formation (TMF) and false memory formation (FMF) were investigated using functional magnetic resonance imaging (fMRI). Using a parametric subsequent memory paradigm, encoding activity was analyzed as a function of whether it predicted subsequent hits to targets (TMF activity) or subsequent false alarms to critical lures (FMF activity). The fMRI analyses yielded 3 main findings. First, the left prefrontal cortex (PFC) was involved in both TMF and FMF activities. This finding is consistent with the evidence that semantic elaboration, which has been associated with left PFC, tends to enhance both true and false remembering. Second, the left posterior medial temporal lobes (MTLs) contributed to TMF but not to FMF activity. This finding is consistent with the notion that MTL is involved in the storage of a consciously, but not unconsciously, processed event. Third, late visual regions were engaged in both TMF and FMF activities, whereas early visual areas were involved primarily in TMF activity. This dissociation indicates that elaborative perceptual processing, but not basic sensory processing, contributes to false remembering. Taken together, the results suggest that FMF is an unintended consequence, or by-product, of elaborative semantic and visual encoding processes.