Cerebral responses to self-initiated action during social interactions

A novel risk variant block across introns 36-45 of CACNA1C for schizophrenia: a cohort-wise replication and cerebral region-wide validation study

OBJECTIVES

Numerous genome-wide association studies have identified CACNA1C as one of the top risk genes for schizophrenia. As a necessary post-genome-wide association study (GWAS) follow-up, here, we focused on this risk gene, carefully investigated its novel risk variants for schizophrenia, and explored their potential functions.

METHODS

We analyzed four independent samples (including three European and one African-American) comprising 5648 cases and 6936 healthy subjects to identify replicable single nucleotide polymorphism-schizophrenia associations. The potential regulatory effects of schizophrenia-risk alleles on CACNA1C mRNA expression in 16 brain regions (n = 348), gray matter volumes (GMVs) of five subcortical structures (n = 34 431), and surface areas and thickness of 34 cortical regions (n = 36 936) were also examined.

RESULTS

A novel 17-variant block across introns 36-45 of CACNA1C was significantly associated with schizophrenia in the same effect direction across at least two independent samples (1.8 × 10-4 ≤ P ≤ 0.049). Most risk variants within this block showed significant associations with CACNA1C mRNA expression (1.6 × 10-3 ≤ P ≤ 0.050), GMVs of subcortical structures (0.016 ≤ P ≤ 0.048), cortical surface areas (0.010 ≤ P ≤ 0.050), and thickness (0.004 ≤ P ≤ 0.050) in multiple brain regions.

CONCLUSION

We have identified a novel and functional risk variant block at CACNA1C for schizophrenia, providing further evidence for the important role of this gene in the pathogenesis of schizophrenia.

Rejection Distress Suppresses Medial Prefrontal Cortex in Borderline Personality Disorder

BACKGROUND

Borderline personality disorder (BPD) is characterized by an elevated distress response to social exclusion (i.e., rejection distress), the neural mechanisms of which remain unclear. Functional magnetic resonance imaging studies of social exclusion have relied on the classic version of the Cyberball task, which is not optimized for functional magnetic resonance imaging. Our goal was to clarify the neural substrates of rejection distress in BPD using a modified version of Cyberball, which allowed us to dissociate the neural response to exclusion events from its modulation by exclusionary context.

METHODS

Twenty-three women with BPD and 22 healthy control participants completed a novel functional magnetic resonance imaging modification of Cyberball with 5 runs of varying exclusion probability and rated their rejection distress after each run. We tested group differences in the whole-brain response to exclusion events and in the parametric modulation of that response by rejection distress using mass univariate analysis.

RESULTS

Although rejection distress was higher in participants with BPD (F1,40 = 5.25, p = .027, η2 = 0.12), both groups showed similar neural responses to exclusion events. However, as rejection distress increased, the rostromedial prefrontal cortex response to exclusion events decreased in the BPD group but not in control participants. Stronger modulation of the rostromedial prefrontal cortex response by rejection distress was associated with higher trait rejection expectation, r = -0.30, p = .050.

CONCLUSIONS

Heightened rejection distress in BPD might stem from a failure to maintain or upregulate the activity of the rostromedial prefrontal cortex, a key node of the mentalization network. Inverse coupling between rejection distress and mentalization-related brain activity might contribute to heightened rejection expectation in BPD.

History of suicide attempts associated with the thinning right superior temporal gyrus among individuals with schizophrenia

Individuals with schizophrenia have higher rates of suicide attempts than the general population. Specific cortical abnormalities (e.g., the cortical surface area and thickness) may be associated with a history of suicide attempts. We recruited 74 individuals with schizophrenia (37 suicide attempters were individually matched with 37 non-attempters on age, sex, phase of illness, and study center) and 37 healthy volunteers. The cortical surface area and thickness data were extracted from structural MRI and compared between the groups. Suicide attempters showed significantly smaller surface areas in the whole brain (p = .028, Cohen's d = -0.54) than non-attempters. No association was found between the cortical surface area of individual brain regions and a history of suicide attempts. The mean cortical thickness did not differ significantly between the groups; however, suicide attempters demonstrated a thinner cortex in the right superior temporal gyrus (p < .001, q = 0.037, Cohen's d = -0.88). These findings indicate that a history of suicide attempts among individuals with schizophrenia is associated with a reduction in the global cortical surface area and specific cortical thinning of the right superior temporal gyrus. The morphometric alteration of the right superior temporal gyrus may represent a biomarker of suicidal behavior in individuals with schizophrenia.

Increased pSTS activity and decreased pSTS-mPFC connectivity when processing negative social interactions

We have previously shown that activity and connectivity within and between the action observation and mentalizing brain systems reflect the degree of positive dimensions expressed by social interactions such as cooperativity and affectivity, respectively. Here we aim to extend this evidence by investigating the neural bases of processing negative dimensions of observed interactions, such as competition and affective conflict, possibly representing a benchmark for different pathological conditions. In this fMRI study 34 healthy participants were shown pictures depicting interactions characterized by two crossed dimensions, i.e. positively- vs. negatively- connotated social intentions mainly expressed in terms of motor acts vs. mental states, i.e. cooperative, competitive, affective and conflicting interactions. We confirmed the involvement of the action observation and mentalizing networks in processing intentions mainly expressed through motor acts (cooperative/competitive) vs. mental states (affective/conflicting), respectively. Results highlighted the selective role of the left pSTS/TPJ in decoding social interactions, even when compared with parallel actions by non-interacting individuals. Its right-hemispheric homologue displayed stronger responses to negative than positive social intentions, regardless of their motor/mental status, and decreased connectivity with the medial prefrontal cortex (mPFC) when processing negative interactions. The resulting mPFC downregulation by negative social scenes might reflect an adaptive response to socio-affective threats, via decreased mentalizing when facing negative social stimuli. This evidence on the brain mechanisms underlying the decoding of real complex interactions represents a baseline for assessing both the neural correlates of impaired social cognition, and the effects of rehabilitative treatments, in neuro-psychiatric diseases or borderline conditions such as loneliness.

Perceived burdensomeness and neural responses to ostracism in the Cyberball task

Previous studies have identified the brain correlates of social pain processing during ostracism. However, the affective response to ostracism may vary according to individual differences in interpersonal needs and subsequent social actions. Despite this relationship, how the neural processes underlying ostracism may be modulated by interpersonal needs to regulate prosocial behaviors remains unknown. Here, in an fMRI study of 64 adults performing the Cyberball task, we quantified ball catching and tossing response time (RT) as a behavioral measure of participants' willingness to seek and reciprocate social interactions. Neural activations to social exclusion were identified and characterized in relation to individual differences in behavioral performance and perceived burdensomeness (PB), a measure of interpersonal needs. The results showed that social exclusion elicited activity in the anterior insula, middle frontal gyrus, postcentral gyrus, and dorsomedial prefrontal cortex, replicating previous studies on ostracism. Importantly, those with higher PB also exhibited greater brain activations to exclusion as well as reduced prosocial behaviors, as reflected by slower ball catching and tossing RT in the Cyberball task. Taken together, these findings suggest that emotional distress in ostracism may increase with PB, resulting in stronger neural responses to social pain and behavioral avoidance of social interactions.

Concurrent amygdalar and ventromedial prefrontal cortical responses during emotion processing: a meta-analysis of the effects of valence of emotion and passive exposure versus active regulation

Anatomically interconnected, the ventromedial prefrontal cortex (vmPFC) and amygdala interact in emotion processing. However, no meta-analyses have focused on studies that reported concurrent vmPFC and amygdala activities. With activation likelihood estimation (ALE) we examined 100 experiments that reported concurrent vmPFC and amygdala activities, and distinguished responses to positive vs. negative emotions and to passive exposure to vs. active regulation of emotions. We also investigated whole-brain experiments for other regional activities. ALE and contrast analyses identified convergent anterior and posterior vmPFC response to passive positive and negative emotions, respectively, and a subregion in between to mixed emotions. A smaller area in the posterior ventral vmPFC is specifically involved in regulation of negative emotion. Whereas bilateral amygdala was involved during emotional exposure, only the left amygdala showed convergent activities during active regulation of negative emotions. Whole-brain analysis showed convergent activity in left ventral striatum for passive exposure to positive emotions and downregulation of negative emotions, and in the posterior cingulate cortex and ventral precuneus for passive exposure to negative emotions. These findings highlight contrasting, valence-specific subregional vmPFC as well as other regional responses during passive exposure to emotions. The findings also suggest that hyperactivation of the vmPFC is associated with diminished right amygdala activities during regulation of negative emotions. Together, the findings extend the literature by specifying the roles of subregional vmPFC and amygdala activities in emotion processing.

The effects of age on cerebral responses to self-initiated actions during social interactions: An exploratory study

Self-initiated action is critical to social interaction and individuals with social anxiety find it particularly difficult to initiate social interactions. We showed earlier that social exclusion encumbered self-initiated actions in the Cyberball task in young adults. Here, we examined whether the behavioral performance and regional responses during self-initiated actions vary with age in 53 participants (21-74 years; 27 men). Behaviorally, participants were slower in tossing the ball during exclusion (EX) than during fair game (FG) sessions in both men and women. In women but not in men the reaction time (RT) burden (RT_EX - RT_FG; RT prolonged during social exclusion) of ball toss was positively correlated with age despite no observed sex difference in Social Interaction Anxiety Scale scores. The pregenual anterior cingulate cortex, thalamus, left occipital cortex (OC) and left insula/orbitofrontal cortex responded to ball toss in EX vs. FG in negative correlation with age in women but not in men. Further, the activation of left OC fully mediated the relationship between age and RT burden in women. Thus, older women are more encumbered in self-initiated action during social exclusion, although this behavioral burden is not reflected in subjective reports of social anxiety. Age-related diminution in OC activities may reflect the neural processes underlying the difficulty in initiating social interactions in women. Together, the findings identified age-sensitive behavioral and neural processes of self-initiated action in the Cyberball task and suggest the importance of considering age and sex differences in studies of social interaction.

Social anxiety, posterior insula activation, and autonomic response during self-initiated action in a Cyberball game

BACKGROUND

An earlier study characterized the neural correlates of self-initiated actions in a Cyberball game in healthy individuals. It remains unclear how social anxiety may influence these neural processes.

METHODS

We examined regional activations to self-initiated actions in 25 adults with low and 25 with high social anxiety (LA and HA, respectively). Skin conductance was recorded concurrently with fMRI. We followed published routines in the analyses of imaging and skin conductance data.

RESULTS

We hypothesized that HA as compared to LA individuals would demonstrate increased cortical limbic activations during self-initiated actions (tossing or T > receiving or R trials, to control for motor activities) in social exclusion (EX) vs. fair game (FG) scenario. At a corrected threshold, HA as compared with LA group showed increases in bilateral posterior insula activation during T vs. R trials in EX as compared to FG. Further, HA as compared to LA showed higher skin conductance response to tossing trials during EX as compared to FG.

LIMITATIONS

With a limited sample size, we did not examine potential sex effects. Further, we cannot rule out the effects of depression on the findings.

CONCLUSIONS

Together, the results suggest that individuals with more severe social anxiety engaged the somatosensory insula to a greater extent and exhibited higher physiological arousal when initiating ball toss during social exclusion in the Cyberball game. Posterior insula response to self-initiated action may represent a biomarker of social anxiety. It remains to be investigated whether interventions to decrease physiological arousal may alleviate social anxiety.