Medial prefrontal cortex has a causal role in selectively enhanced consolidation of emotional memories after a 24-hour delay: An iTBS study

Previous research points to an association between retrieval-related activity in the medial prefrontal cortex (mPFC) and preservation of emotional information compared to co-occurring neutral information following sleep. Although the role of the mPFC in emotional memory likely begins at encoding, little research has examined how mPFC activity during encoding interacts with consolidation processes to enhance emotional memory. This issue was addressed in the present study using transcranial magnetic stimulation in conjunction with an emotional memory paradigm. Healthy males and females encoded negative and neutral scenes while undergoing concurrent TMS with an intermittent theta burst stimulation (iTBS) protocol. Participants received stimulation to either the mPFC or an active control site (motor cortex) during the encoding phase. Recognition memory for scene components (objects and backgrounds) was assessed after a short (30 minutes) and a long delay (24-hours including a night of sleep) to obtain measures of specific and gist-based memory processes. The results demonstrated that, relative to control stimulation, iTBS to the mPFC enhanced gist, but not specific, memory for negative objects on the long delay test. mPFC stimulation had no discernable effect on gist memory for objects on the short delay test nor on the background images at either test. These results suggest that mPFC activity occurring during encoding interacts with consolidation processes to selectively preserve the gist of negatively salient information. Significance StatementUnderstanding how emotional information is remembered over long delays is critical to understanding memory in the real world. The present study uses transcranial magnetic stimulation (TMS) to investigate the interplay between mPFC activity that occurs during memory encoding and its subsequent interactions with post-encoding consolidation processes. Excitatory TMS delivered to the mPFC during encoding enhanced gist-based memory for negatively valenced pictures on a test following a 24-hr delay, with no such effect on a test occurring shortly after the encoding phase. These results are consistent with the hypothesis that emotional aspects of memories are differentially subjected to consolidation processes, and that the mPFC might contribute to this "tag-and-capture" mechanism during the initial formation of such memories.