The Effect of Social Support on Frontal Asymmetry: Neural Reactivity to Social Support and Longitudinal Outcomes

The perception of adequate social support is associated with an extension of life expectancy of the same magnitude as many recommended health behaviors (Holt-Lunstad et al., 2010). Mechanistic pathways proposed to explain this phenomena include biological (Ozbay et al., 2007; Reblin & Uchino, 2008)⁠, behavioral (Reblin & Uchino, 2008; Umberson, 1987)⁠, and psychological (Uchino et al., 1996, 2012)⁠ pathways. However, the extant literature has not examined the means by which perceived social support exerts benefits through these pathways, and there is a need for theory-driven investigations into intermediary mechanisms. This dissertation study proposes a theoretical framework, Social Augmentation of Approach/Avoidance Theory (SAAT), which establishes falsifiable hypotheses about a specific intermediary pathway: social alterations of approach and avoidance motivation. This dissertation then systematically tests hypotheses generated by SAAT through a series of analyses utilizing electroencephalographic (EEG) and functional resonance magnetic imagining (fMRI) data.

The participants in the two datasets used in this dissertation (N = 74 and 71 respectively) underwent a threat of shock task, during which they were either alone or being supported by a chosen partner. Partners supported the participants being threatened by holding hands. This task has been shown to index neural differences between the two conditions (i.e., being threatened while alone and being threatened while holding a partner’s hand) associated with decreased threat processing (L. A. Beckes et al., 2020; Coan, Schaefer, et al., 2006; Maresh et al., 2013)⁠. Participants in the first dataset completed measures of current psychopathology during the visit where they underwent the hand holding task. Participants in the second dataset were part of a larger, longitudinal study, with measure of psychopathology and physiological health collected extensively over 15 years. Participants in the first study underwent the threat of shock task with support from a romantic partner. Participants in the second study underwent the task with a partner of their choosing. These included a mixture of friends, cohabiting romantic partner, and non-cohabiting romantic partners.

Study 1 tested whether receiving social support, in the form of supportive touch during threat of shock, is associated with an increase in approach motivation compared to being alone. I utilized a well-established index of approach/avoidance motivation, frontal alpha asymmetry (Coan & Allen, 2003a, 2003b, 2004; Kelley et al., 2017; Stewart et al., 2011, 2014)⁠, processed using EEG taken during the hand holding task. I also investigated current psychopathology as a moderator of frontal asymmetry during the task. Results indicated an overall decrease in left frontal activity when seeing threatening cues, but no effect on right frontal activity or the overall asymmetry index. Similarly, left frontal activity was sensitive to current depression symptoms and condition (alone or with partner), but neither right frontal activity nor overall asymmetry was affected.

Study 2 expanded on the initial findings in Study 1 by incorporating longitudinal data and testing the sensitivity of asymmetry in specific brain systems to supportive touch during threat. Participants were scanned using fMRI during the same hand holding task outlined above. Asymmetry was calculated using a previously validated fMRI laterality index for masks of the amygdala and an executive control network (ECN) containing the dorsolateral prefrontal cortex (dlPFC). These laterality indexes were calculated from contrasts of activity during threat cues minus activity during safety cues. I examined whether asymmetry in either brain system was altered when seeing different cues, and whether previous psychopathology and the relationship with the supporting individual moderated these effects. Results indicated more leftward activity when receiving social support in both the amygdala and ECN. However, psychopathology factors moderated this pattern in the amygdala. Hand holding was associated with different changes in amygdala laterality depending on the interaction between relationship type and previous depressive episodes. Anxiety history also moderated the effect of hand holding on amygdala laterality.

I continued my analyses in study 2 by examining whether individual differences in laterality sensitivity to hand holding mediated or moderated the relationship between perceived social support and a number of physiological health and behavior measures taken in the years following participants visit to the scanner. Results of these analyses did not align with hypotheses generated theoretically, and no significant moderation or mediation effects were found.

Results of these two studies were mixed when it came to testing hypotheses generated from the SAAT framework. I conclude this dissertation by discussing the results in the context of the extant literature, elaborating on potential limits of the presented studies, and future directions to further test intermediary pathways between social support, psychological health outcomes, and physical health outcomes.