Emotion regulation by cognitive reappraisal - the role of frontal theta oscillations.

The regulation of emotion by cognitive reappraisal has attracted a lot of attention over the last decade. Studies using functional magnetic resonance imaging (fMRI) revealed a wide-spread network of multiple prefrontal and sub-cortical brain regions involved in the successful decrease of negative emotions. However, less is known about the temporal dynamics and the physiological mechanisms underlying these regulation processes. Synchronization of neural oscillations in specific frequency bands plays a key-role in the long-range interaction of different brain regions and oscillatory coupling in the theta frequency range was recently identified to play an important role in the interaction of prefrontal structures, the amygdala and the hippocampus in animal models. Accordingly, we investigated the role of prefrontal theta oscillations during the cognitive reappraisal of aversive pictures in humans. We hypothesized an increase in frontal theta oscillations during emotion regulation and a relationship between frontal theta power and the subjective success of emotion regulation. EEG from 30 healthy participants was recorded while they were asked to passively watch or reappraise the content of pictures with negative content. As expected, we found a significant increase in frequencies around 4Hz at electrode Fz during the regulation condition 'decrease' compared to the 'maintain' condition (p=.006) as well as for the regulation condition 'increase' compared to the 'maintain' condition (p=.017). Additionally, the strength of theta power was positively correlated with the regulation success as reported by the participants (r=0.463, p<.05). The estimation of possible generators of the theta oscillations was done using standardized low resolution electromagnetic tomography (sLORETA). Results suggested the left middle/inferior frontal gyrus as a possible generator. The results of the present study are in line with previous findings of fMRI studies suggesting the same regions as part of the regulation network and provide a first direct link between the imaging based knowledge of emotion regulation and a possible physiological mechanism.