Repeated transcranial magnetic stimulation on dorsolateral prefrontal cortex improves performance in emotional memory retrieval as a function of level of anxiety and stimulus valence.

AIMS: Anxiety behavior showed a consistent attentional bias toward negative and aversive memories, induced by a right frontal cortical superiority, based on an unbalance effect between the two hemispheres. The aim of the present study was to explore the role of the left dorsolateral prefrontal cortex (DLPFC) in the memory retrieval process of positive versus negative emotional stimulus, as a function of anxiety level.
METHODS: A repeated transcranial magnetic stimulation (rTMS) paradigm was used to induce cortical activation of the left DLPFC. Subjects (n = 27; age range, 21-36 years), who were divided into two different groups (high/low anxiety; State-Trait Anxiety Inventory), were required to perform a task consisting of two experimental phases: an encoding phase (lists composed of positive and negative emotional words); and a retrieval phase (old stimuli and new stimuli to be recognized). Moreover, new stimuli (distractors) semantically related or unrelated to the old stimuli were used to test a possible interference effect induced by the semantic association.
RESULTS: rTMS over the left DLPFC affects memory retrieval. High-anxiety subjects benefited in greater measure from frontal left stimulation with a reduced negative bias (increased accuracy and reduced response time for the positive stimuli) and a significant increased performance for the semantically related distractors (reduced interference effect).
CONCLUSION: Left DLPFC activation favors the memory retrieval of positive emotional information and might limit the unbalance effect induced by right hemispheric superiority in high levels of anxiety.