Overall, our results indicate that the neural circuitry associated with either producing or regulating the feelings of distress when being excluded by peers is similar to that which has been found among adults experiencing social exclusion in previous research. However, our findings also indicate that adolescents may experience social exclusion by peers in unique ways. Such a discovery may contribute to our understanding of why peer rejection is so salient during this developmental time period.
As predicted, during exclusion compared to inclusion, adolescents displayed reliable activity consistent with that seen previously among adults, including significant activity in the insula, a region associated with visceral pain and negative affect (Augustine,
1996; Buchel
et al.,
1998; Gorno-Tempini
et al.,
2001; Phillips
et al.,
2003,
2004). Furthermore, analyses suggested that individuals with greater activity in the insula felt more social distress in response to social exclusion, a finding consistent with prior work linking insular activity to neural responses during social exclusion (Eisenberger
et al.,
2003). Also in line with previous adult studies, adolescents showed activity in the right VLPFC that was related to lower reports of distress, and interregional correlational analyses confirmed right VLPFC activity was negatively correlated with activity in the insula, subACC and dACC, consistent with previous work showing that this region plays a role in regulating negative affect (Hariri
et al.,
2000; Eisenberger
et al.,
2003; Lieberman
et al.,
2004,
2007). Thus, RVLPFC may play an important role in regulating distress following exclusion during adolescence.
Interestingly, there were a few regions that either did not show the same pattern of activity in adolescents as they have in adults or have not been previously observed in studies of social exclusion among adults. For instance, although dACC activity has been consistently shown among adult samples to be related to the distress experienced during social exclusion (e.g. Eisenberger
et al.,
2003), a similar relationship between dACC activity during exclusion and distress was not found among adolescents. This difference was unexpected; however, it is not surprising given the differences in the salience, prevalence and meaning of social rejection when comparing adults and adolescents. In addition, among adolescents, subACC activity was found during exclusion compared to inclusion and this activity was correlated with higher reports of distress following exclusion. This is contrary to previous work in adults showing that the subACC is involved in more positive affective processes, including social acceptance (Somerville
et al.,
2006), lower rejection sensitivity (Burklund
et al.,
2007), optimism (Sharot
et al.,
2007) and positive interpretations of negative stimuli (Kim
et al.,
2003). Thus, it is not clear why the subACC is associated with greater self-reported distress in adolescents; however, it should be noted that research with clinical populations has shown reverse effects as well, such that greater subACC activity was associated with higher levels of depression (Chen
et al.,
2007; Keedwell
et al.,
2008). It is possible that adolescents may show patterns of subACC activity more similar to clinical samples than adults either because adolescents display greater emotional reactivity than adults, or because of the ongoing development of this region during adolescence (e.g. Gogtay
et al.,
2004).
Finally, an additional unique finding from this study indicated that adolescents displayed significant activation in the VS during exclusion compared to inclusion, and that VS activity was negatively correlated with subjective distress. An interregional correlational analysis revealed that this area of the VS was negatively correlated with the insula, subACC and dACC, suggesting that this region may be crucial for regulating negative affect during adolescence. Although not predicted, this finding fits with recent work showing that the VS is involved in successful emotion regulation. The VS has consistently been shown to be involved in reward learning and approach motivation more generally (McClure
et al.,
2003; Schultz,
2004, Tindell
et al.,
2006; Wager
et al.,
2007) and in a recent study, greater activity in the VS when reappraising aversive images related to greater reappraisal success (Wager
et al.,
2008). This previous work supports the hypothesis that VS activity may play a role in affect regulation by aiding in the reinterpretation of stimuli in positive ways. Moreover, the positive associations between the VS and the right VLPFC seen in the current study replicate previous work (Wager
et al.,
2008) and suggest that these areas could potentially be active simultaneously to aid in affect regulation.
In support of this theory, research in clinical populations among individuals with atypically functioning prefrontal regions (e.g. bipolar patients) has demonstrated that the VS supports regulation of responses to emotionally salient stimuli (e.g. Dickstein and Leibenluft,
2006; Marsh
et al.,
2007). One interpretation of these clinical findings is that the VS may play a compensatory role for some of the functions typically supported by the prefrontal cortex, and thus VS activity may be heightened among populations with atypically functioning prefrontal regions during tasks requiring regulatory processing. Since the prefrontal cortex continues to develop both structurally and functionally through late adolescence (Giedd
et al.,
1999; Gogtay
et al.,
2004; Sowell
et al.,
2004), and is thus not ‘typically functioning’ relative to adults, the VS may provide an alternate means of regulating negative emotion among typically-developing adolescents, in ways similar to clinical populations. In general, these kinds of discrepancies in frontal lobe maturity may help to explain behavioral differences in responses to emotion-evoking stimuli across ages as well as why certain experiences, like peer rejection, appear to have a developmental time frame during which they are particularly salient and distressing.
In addition to our analyses examining neural correlates of distress and regulation of distress during exclusion by peers, we examined how rejection sensitivity and interpersonal competence modulated neural activity during exclusion. We found that adolescents who reported themselves as being more sensitive to peer rejection displayed greater activity in the dACC, precuneus and anterolateral PFC. This association with the dACC is consistent with previous research with adults indicating that increased activity in the dACC is associated with greater social distress following social exclusion (Eisenberger
et al.,
2003) and greater rejection sensitivity (Burklund
et al.,
2007). The precuneus has previously been found to be linked to mentalizing tasks including imagery (Cavanna and Trimble,
2006) and both direct and reflected self-appraisals (Pfeifer
et al., in press), and thus our finding supports the possibility that adolescents who are more sensitive to rejection may be more concerned with the other players’ thoughts and motivations for excluding them.
Finally, the association between parent-reported interpersonal competence and neural activity during exclusion revealed that adolescents whose parents perceived them as being more socially competent showed heightened activity in the dACC and insula, two regions found to be related to exclusion in previous research (e.g. Eisenberger
et al.,
2003). These findings suggest that heightened interpersonal skills among adolescents is linked with increased neural sensitivity to exclusion by peers. Although somewhat counterintuitive, this is consistent with behavioral research indicating that adolescents with high interpersonal competence are more conscious of peer norms, more advanced cognitively, and more sensitive to others’ emotions (Dekovic and Gerris,
1994; Allen
et al.,
2005), which leaves them more sensitive to relational problems with peers (Hoglund
et al.,
2008).
Also consistent with this hypothesis, more interpersonally competent adolescents displayed greater activation in the right VLPFC and VS during exclusion, suggesting that interpersonally competent adolescents may also be engaging in more regulation of distress related to being rejected—either because their heightened distress produces a greater need for regulation, or because they are better at regulating. Consistent with the second of these explanations, behavioral research has shown that even interpersonally competent individuals who appear less affected by peer rejection, are actually similarly distressed by rejection; however, they are better able to recover from rejection experiences using problem-solving and reasoning as coping methods that result in a relatively faster attenuation of negative mood than other children (Reijntjes
et al.,
2006).
Overall these findings suggest that, similar to adolescents who report being more sensitive to rejection, individuals whose parents perceive them to be more interpersonally competent show more neural sensitivity to a simulated experience of peer rejection. Furthermore, in the context of previous research with adults experiencing social exclusion, these findings may suggest that the neural structures that support social exclusion experiences among adults are particularly sensitive to peer exclusion among adolescents who evidence heightened sensitivity to negative social encounters with peers, (i.e. more interpersonal competence and/or rejection sensitivity.