تنظیم احساسات خود به خود: اثرات مختلف بر روی پتانسیل های برانگیخته مغز و فعالیت ماهیچه های صورت

Abstract Late positive potentials (LPPs) were found to be decreased during down-regulation and increased during up-regulation of positive and negative emotions. However, previous studies lack ecological validity, since they explicitly instructed their participants to use certain regulation strategies. The goal of our study was to test an ecologically more valid paradigm of emotion regulation. We therefore investigated the effects of freely chosen emotion regulation strategies on LPPs and additionally assessed facial EMG responses and valence and arousal ratings as control variables. Responses to positive IAPS pictures were marked by pleasant valence ratings and high activations of M. zygomaticus major, negative pictures elicited unpleasant valence ratings and high activations of M. corrugator supercilii, and both, positive and negative pictures, went along with increased arousal ratings and LPPs. Importantly, ratings and EMG activity were intensified through up-regulation and attenuated through down-regulation of emotions, while LPPs were increased through both up-and down-regulation. We conclude that LPPs in paradigms with free choice of emotion regulation strategies might be a marker of attentional resources required for the selection of adequate emotion up- and down-regulation strategies, while LPP effects following emotion regulation with specific, instructed strategies reflect modulated arousal processes.

. Introduction Emotion regulation is essential for an adaptive functioning in social interactions. Numerous psychological disorders go along with deficits in emotion regulation (Aldao et al., 2010, Berking and Wupperman, 2012, Cole and Deater-Deckard, 2009 and Gross and Levenson, 1997). According to a process model of emotion regulation (Gross, 1998 and Gross, 2002), emotional reactions may be influenced at different steps of the emotion generation process. As antecedent-focused strategies, Gross, 1998 and Gross, 2002 identified situation selection, attentional deployment, and reappraisal. Attentional deployment and reappraisal have mostly been investigated in experimental studies (Foti and Hajcak, 2008, Hajcak and Nieuwenhuis, 2006, Hajcak et al., 2006, Johnson, 2009, Krompinger et al., 2008, McRae et al., 2012, Shiota and Levenson, 2012 and Wu et al., 2012). The last step in this model is the response-focused suppression of an emotional reaction. These studies revealed that antecedent-focused emotion regulation strategies are more effective than response-focused emotion regulation (Gross and John, 2003 and Gross and Levenson, 1997) and are a crucial part of many psychotherapeutic programs (Aldao and Mennin, 2012, Barlow, 2008, Clark and Beck, 2012, Herbert and Forman, 2011, Philipsen et al., 2007, Price et al., 2012, Smits et al., 2012, Totterdell et al., 2012 and Linehan, 1993). The neural correlates of emotion regulation have been investigated through the modulation of late positive potentials (LPPs; Dennis and Hajcak, 2009, Hajcak and Nieuwenhuis, 2006, Hajcak et al., 2010 and Langeslag and van Strien, 2010), a special component of event-related brain potentials (ERPs). LPPs are positive electrophysiological deflections which appear relatively late after stimulus onset (from 400 ms up to several seconds after stimulus onset). The LPP amplitude was found to be modulated by emotional stimuli (Hajcak et al., 2010 and Lang and Bradley, 2010) with larger amplitudes related to an increase in arousal. Thus, a broad range of empirical work revealed larger LPP amplitudes up to 2000 ms, in one study even up to 6 s after stimulus onset, mostly in centro-parietal brain regions after the presentation of pleasant or unpleasant, compared to neutral pictures (Amrhein et al., 2004, Cuthbert et al., 2000, Hajcak et al., 2007, Pastor et al., 2008 and Schupp et al., 2000). In addition, up-regulation of emotions went along with an amplification of LPP amplitudes, while down-regulation led to diminished LPPs in studies where participants were trained to apply certain emotion regulation strategies according to Gross's (Gross, 1998 and Gross, 2002) model of emotion regulation, such as attention allocation (Dunning and Hajcak, 2009 and Hajcak et al., 2006) or reappraisal strategies (Dennis and Hajcak, 2009, Foti and Hajcak, 2008, Hajcak and Nieuwenhuis, 2006, MacNamara et al., 2011a, MacNamara et al., 2011b and Moser et al., 2009). Therefore, it was concluded that changes in LPP amplitude due to emotion regulation reflect modulations in the elicited arousal. However, because nearly all previous studies provided instructions of specific emotion regulation strategies, there is little knowledge about naturalistic emotion regulation when participants are free to choose and develop individual regulation strategies. To our knowledge the only emotion regulation study measuring LPP amplitudes without specific strategy instructions so far (Langeslag and van Strien, 2010) found increased LPP amplitudes in both up- and down-regulation conditions, compared to a non-regulation condition (still, the LPP increase in the up-regulation condition was larger than in the down-regulation condition). Since this pattern of results contrasts the majority of LPP effects related to emotion regulation, a replication of the Langeslag and van Strien (2010) study with improved methodology is warrant to decide whether a spontaneously applied emotion regulation strategy indeed has unique effects on LPPs. Accordingly, we intended to investigate emotion regulation effects on LPP amplitudes under a free strategy choice (without training in advance) with the following methodological improvements. In contrast to Langeslag and van Strien who used a block design with varying orders across participants, we realized a completely randomized trial order. Moreover, to gain a complete picture of naturalistic emotion regulation, we considered it important to investigate regulation of both positive and negative emotions, at central and parietal brain regions and different time frames, and also with various biopsychological measures. Whereas Langeslag and van Strien (2010) assessed modulations of LPPs only up to 1000 ms after stimulus onset, we investigated LPP modulations up to 4000 ms after stimulus onset and also measured EMG modulations as a manipulation check. This approach to further investigate emotion regulation without specific strategy instructions seems important to increase the ecological validity of such studies. In everyday life, we continuously have to regulate our emotions without being trained to do so in a specific way beforehand. Additionally, it is known that patients with psychiatric disorders often suffer from emotion regulation deficits (Aldao and Dixon-Gordon, 2014 and Gross, 2002). A straightforward assessment of their deficient emotion regulation capabilities requires a paradigm without strategy training because such strategy training would already function as some sort of psychotherapeutic intervention. Our research question was whether emotion regulation also works under free choice of regulation strategies in healthy subjects. We therefore investigated emotion regulation effects on ratings of affect, LPPs and facial EMG responses during free strategy choice. Facial EMG of M. zygomaticus major and of M. corrugator supercilii as indicator of pleasant and unpleasant affective valence, respectively, has been found to be a good marker of emotion regulation as those muscles' activity increases from down-, to not-, to up-regulation during the corresponding emotions (Jackson et al., 2000 and Wu et al., 2012). As a matter of fact, the present study is to our knowledge the first combining EEG and EMG measurements during emotion regulation. The assessment of EEG, EMG, and valence and arousal ratings during emotion regulation allows a direct comparison of different implicit and explicit emotion and regulation effects and allows further conclusions about the interpretation of changes in LPPs. In addition, we planned to study emotion regulation after both pleasant and unpleasant pictures, while most previous studies concentrated on the investigation of either positive or negative emotions compared to neutral affective states (Dunning and Hajcak, 2009, Foti and Hajcak, 2008, Hajcak and Nieuwenhuis, 2006, Krompinger et al., 2008, MacNamara et al., 2011a, MacNamara et al., 2011b and Paul et al., 2013). Recent research (Poole and Gable, 2014) has also shown that approach vs. avoidance related emotional motivation influences the amplitude of the left vs. right frontal LPP differentially. In this study, frontal LPPs elicited by approach-positive and approach-negative pictures were larger in left vs. right frontal regions. LPPs elicited by withdrawal-negative pictures, however, did not differ between left and right frontal regions. For the mere emotion induction by simply watching affective pictures, we expected higher respectively lower valence ratings for pleasant respectively unpleasant, compared to neutral pictures. Moreover, we hypothesized that arousal ratings and LPP amplitudes would be comparably high for pleasant and unpleasant pictures and higher than for neutral pictures. M. zygomaticus major activation should be higher for pleasant than for unpleasant and neutral images, whereas M. corrugator supercilii activation should be higher for unpleasant compared to pleasant and neutral images. Concerning the regulation of emotions, we expected valence and arousal ratings as well as M. zygomaticus major respectively M. corrugator supercilii activations to be intensified by the up-regulation and attenuated by the down-regulation conditions. In line with the findings of several classical LPP-studies on emotion regulation where participants used specifically instructed and trained regulation strategies, we also expected LPP amplitudes to be intensified by up- and attenuated by down-regulation of both positive and negative emotions. Alternatively, in line with the only other previous study investigating spontaneously applied emotion regulation strategies and LPPs (Langeslag and van Strien, 2010), it would be also possible to detect increased LPPs during both up- and down-regulation conditions.

5. Conclusions In sum, we found the expected general emotion induction effects for ratings, EMG and LPP responses well in line with the literature. With respect to emotion regulation under free choice of strategies, rating and EMG data corroborate and extend previous findings. Therefore, we conclude that our participants successfully achieved emotion regulation without emotion regulation strategy training beforehand. Contrary to classical studies with explicitly instructed emotion regulation strategies, we observed enhanced LPPs in both up- and down-regulation conditions. Maybe, attention-processes come into account more strongly than arousal-processes. However, this is speculative and must be clarified in further studies. Overall, our results speak for the validity of our emotion regulation task with free strategy choice which might be a fruitful experimental approach to detect emotion regulation dysfunctions in patients.