rTMS stimulation on left DLPFC increases the correct recognition of memories for emotional target and distractor words

According to a recent hypothesis, the prefrontal cortex has been proposed as the site of emotional memory integration, because it is sensitive to the recognition of emotional contents. In the present research, we explored the role of the dorsolateral prefrontal cortex (DLPFC) in memory recognition processes for positive versus negative emotional stimuli when old (target) and new (distractor, either semantically related or unrelated to the target) stimuli were presented. The role of the DLPFC was analysed using an rTMS (repeated transcranial magnetic stimulation) paradigm that induced increased cortical activation of the left DLPFC. The subjects were required to perform a task that consisted of two experimental phases (i.e., an encoding and a recognition phase) in which the targets and the distractors were presented and recognition performance was measured. rTMS stimulation was provided over the left DLPFC during the recognition phase. We found that the rTMS stimulation affected the memory recognition of positive emotional material. Moreover, related and unrelated distractors were discarded better when they were positively valenced, and a more significant effect (i.e., increased performance) was produced in response to related distractors. This result suggests that the activation of the left DLPFC favours the memory recognition of positive emotional information, and that such activation is able to induce a more appropriate selective process to distinguish target from distractor stimuli in the presence of more complex processes (related distractors). The valence model of emotional cue processing may explain this increased performance by demonstrating the distinct role of the left hemisphere in the retrieval of positive emotional information.