Date

2019

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Counseling Psychology

First Adviser

Woohdouse, Susan S.

Abstract

Patterns of respiratory sinus arrhythmia (RSA), an index of parasympathetic nervous system (PNS) activation, are crucial in socioemotional development (Porges & Furman, 2011). Polyvagal theory (Porges, 2007) posits that adaptive patterns of RSA are characterized by flexibility, such that, during challenge, infant RSA lowers, to actively attend to environmental demands and marshal resources to support the infant. When challenge is removed, as in normal social engagement with the mother, infant RSA increases, facilitating a shift towards the PNS and promoting relaxation. The Still-Face paradigm (SFP, Tronick et al., 1978) is useful for studying RSA during social engagement with the mother (2-min), interruption by challenge (2-min of maternal disengagement), followed by 2-minute reunion (maternal reengagement). On average, most infants show adaptive RSA patterns (high RSA, low RSA, high RSA). Group mean data, however, do not fit half of infants (Bazhenova et al., 2001; Moore & Calkins, 2004). The present study represents methodological advances over previous research, which have only examined group means for each episode of the SFP and episode-to-episode changes. The present study used growth mixture models to identify trajectories of RSA across the entire SFP and examine links between trajectories and maternal sensitivity. 197 6-month-old infants and their low-income (35%<$10,000, $10,000>18%<$30,000) mothers (38% African American, 16% White, 24% Multiracial, 13% Latina) participated in a larger study of maternal caregiving. RSA was extracted in 30-second epochs during episodes of the SFP (Porges, 1985). Sensitivity was reliably coded from tapes of normal play and reunion episodes of the SFP. Infant level of distress during the reunion episode was coded by reliable coders. A cubic growth mixture model was tested with mean RSA for each episode of the SFP as data points. Three unique trajectories emerged: unchanging, moderate suppressors, and steep suppressor. Maternal sensitivity predicted classes at levels nearing significance and infant distress predicted classes. The unchanging class contained infants whose RSA stayed around baseline levels over the entire course of the SFP. Compared to the other classes, the infants in the unchanging class had mothers who were highest in maternal sensitivity and infants who were low in distress. The moderate suppressor class contained infants whose RSA stayed in withdrawed levels throughout the SFP, indicating that they experienced the entire SFP like it was a challenge. Compared to the other classes, the infants in the moderate suppressor class had mothers who were lowest in maternal sensitivity and infants who were more distressed. The steep suppressor contained one infant whose RSA sharply withdrew throughout the SFP. This infant’s mother was low in sensitivity and the infant was distressed. Ameliorations of unique and nuaned trajectories of vagal regulation are discussed, in light of the polyvagal theory. Implications for polyvagal theory and future research directions are discussed, specifically how to expand the knowledge about infant phsyiologial development that may not fit into predictions of polyvagal theory. Limitations and clinical applications are also discussed.

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