Page 64 - Like me, or else... - Michelle Achterberg

Chapter 3
following the experience of social rejection, but intriguingly, these effects were dependent on whether the participant showed low or high executive control. Participants who scored high on executive control displayed lower aggression after social rejection, suggesting that executive control abilities may down- regulate aggression tendencies. It has been suggested that self-control relies strongly on the lateral prefrontal cortex (PFC), which is thought to exert top-down control over subcortical, affective, brain regions (such as the striatum) to suppress outputs that otherwise lead to impulsive response and actions (Casey, 2015). Transcranial magnetic stimulant (TMS) studies have indeed implicated a causal role for the lateral PFC in executing self-control when choosing long-term rewards (Figner et al., 2010). Similarly, lateral PFC may have an important role in down-regulating aggression following rejection or negative social feedback. This hypothesis finds support in a study where participants had the opportunity to aggress to peers who had excluded them during Cyberball while undergoing transcranial direct current stimulation (tDCS) (Riva et al., 2015). TDCS of the right ventrolateral (vl) PFC reduced participants’ behavioral aggression to the excluders.
Taken together, prior studies suggested an important role of dorsal and ventral mPFC regions in processing negative and positive social feedback, but the exact contributions of these regions are not consistent across studies and may depend on the experimental paradigm. The first goal of this study was to disentangle effects of positive and negative feedback in a social evaluation paradigm (Somerville et al., 2006). A novel component of this study relative to prior studies is that we included a neutral baseline condition, in which participants received neutral feedback on a subset of the trials. Based on prior research, we expected that positive social feedback would result in increased activation in the subgenual ACC (Somerville et al., 2006) and the ventral striatum (Guyer et al., 2009; Davey et al., 2010; Gunther Moor et al., 2010b). In contrast, we expected that negative social feedback would be associated with increased activity in the dACC/ dorsal medial PFC (dmPFC) and the insula. Prior studies remained elusive about whether dACC/mPFC and insula activity were associated with salient events per se (Somerville et al., 2006) or social rejection specifically (Eisenberger et al., 2003; Kross et al., 2011). Therefore, we conducted conjunction analyses for both positive and negative feedback versus neutral baseline, as well as direct contrasts testing for differences between positive and negative social feedback.
Importantly, there may be individual differences in how participants respond to negative social feedback, which may be associated with increased neural activity in lateral PFC, as has been found in social rejection studies (Chester and DeWall, 2016). The second goal of this study was therefore to examine how individuals respond to negative social feedback, and if lateral PFC activity is related to aggression regulation following negative social feedback. Therefore, the paradigm included a second event where participants could
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