The Role of the Ventromedial Prefrontal Cortex in Mnemonic Discrimination and Generalization

The ventromedial prefrontal cortex (vmPFC) is involved in generalizing across similar items and events, working with hippocampally mediated processes that discriminate between those items and events at encoding. These complementary processes may, in turn, contribute to confidence signals regarding the appropriateness or veracity of retrieved memory traces. In this study, mnemonic discrimination and generalization were assessed in individuals with vmPFC lesions using the Mnemonic Similarity Task (MST; Stark et al., 2013), which was designed to assess the ability to distinguish previously learned images of everyday objects (targets) from unstudied, highly similar images (lures) and dissimilar images (foils). Relative to controls, vmPFC-lesioned participants showed intact discrimination of lures from targets but a propensity to mistake similar lures for dissimilar foils, and were overly confident relative to their accuracy. This pattern of performance is suggestive of a failure to develop a conceptual knowledge framework to extract a gist from common items. The findings suggest that mnemonic discrimination requires a balance of hippocampal and vmPFC interactions to facilitate detailed and gist memory of highly similar input.