Abstract

Temperament is thought to be the foundation for normative personality and subsequent behaviors later in life. To assess the relationship of early temperament with variation in structural brain development, this study examined rhesus macaque mother-infant behavior, and then three years later, used MRI to assess neurostructural differences. Individual differences in mother-infant interactions and emotionality were then linked to brain differences. Extensive behavioral data obtained over the first year of life under both resting and stressful conditions was used to assess the quality of mother-infant interactions and emotionality. The MRI focused on brain volume in areas thought to be related to emotional regulation and such as the cingulate gyrus and corpus callosum structures. These structures are often mentioned as areas that modulate emotions, temperament and general social behavior. The methods involved in this research include behavior coded from group-housed infant rhesus macaques (Macaca mulatta). The subjects were 15 mother-reared subjects, each housed in a social group of 12-20 subjects, living in social settings with their mothers, other adult females, two adult males, and other same-aged subjects; conditions that approximate the social composition of the natural setting. Behaviors related to temperament and mother-infant interactions were assessed using an objective behavioral scoring system. Behavior was coded under three conditions, and each behavioral coding session was 5-minute long. Homecage: Two behavioral coding sessions were recorded weekly for each subject as it interacted naturally with its mother and peers over the first six-months of life. Preseparation (month 6): Two weeks before four, sequential, 4-day social separations, behavioral data were collected once each day. Reunion with mother: Following each of the social separations, data were collected twice immediately following return to mother and again on the morning before the separation. Subjects underwent MRIs 1-2 years later when they were 2-3 years of age. The result of this research was that during pre-separation interactions, anterior cingulate size to brain ratio showed a positive correlation with mutual ventral contact (being cradled and held closely), a measure of the use of mother as a secure base to calm anxiety and fear.

Degree

College and Department

Family, Home, and Social Sciences; Psychology

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