DLPFC, meta-cognitive control and emotional expression. What role of the frontal network for emotion and cogniton in memory mechanisms?

A recent hypothesis proposed that the prefrontal cortex (PFC) may be identified as the site of emotion-memory integration, since it was shown to be particularly sensitive to the encoding and retrieval of emotional contents and it was observed to have a meta-cognitive control on emotional behavior (Balconi & Ferrari, in press). Thus, PFC could be crucial in mechanisms underlying the regulation of emotion, such as inhibition. It was found PFC governs the executive control of information processing, including the ability to inhibit irrelevant stimuli and impulses, and evaluate and select the appropriate response. Specifically a top-down meta-control of PFC on the amygdala allows for a cognitive modulation of emotional processes by frontal brain structures. However, some evidence suggests that multiple regions of the PFC have the capacity to perform multiple types of executive control functions (i.e. evaluate, maintain, inhibit, or select). In particular, evidence indicates that PFC extending to the ventrolateral PFC, could facilitate successful goal-oriented behavior by inhibiting the influence of emotional information in the context of physical sensation, selective attention, and emotion regulation. In the present research we explored the role of the dorsolateral prefrontal cortex (DLPFC) in memory retrieval process of positive vs. negative emotional stimuli when old (target) and new (distractor, semantically related and unrelated to the target) stimuli were presented. This effect was analyzed by using a rTMS (repeated Transcranial Magnetic Stimulation) paradigm that induced an increased cortical activation of the left DLPFC. Subjects were required to perform a task consisting in two experimental phases: an encoding-phase, where some lists composed by positive and negative emotional words were presented to the subjects; a retrieval-phase, where the old stimuli and the new stimuli were presented for a recognition performance. The rTMS stimulation was provided during the retrieval-phase over the left DLPFC. We found that the rTMS stimulation over this area affects the memory retrieval of positive emotional material, with higher memory efficiency (shorter Response Times, RTs). Moreover, related and unrelated distractors were better discarded when they were positively valenced, and the more significant effect was produced in response to related distractors with an increased effectiveness (better accuracy) and efficiency (reduced RTs). This result suggested that left DLPFC activation favours the memory retrieval of positive emotional information and secondly that it is able to induce a more appropriate selective process to distinguish target from distractor stimuli. The valence model of emotional cue processing may explain the increased performance, by pointing out the distinct role the left hemisphere has in positive emotional information recall.