PRELIMINARY INVESTIGATIONS OF DOPAMINERGIC CONTRIBUTIONS TO PRESCHOOLERS’ THEORY OF MIND DEVELOPMENT by

During the preschool years, children across all cultures that have been tested seem to come to an explicit understanding of the fact that mental states are related to but ultimately separate from the reality that they are meant to represent. This understanding is sometimes called a representational theory of mind (RTM). I hypothesized that the neurotransmitter dopamine (DA) would be associated with RTM development in preschoolers. I selected DA because several lines of work now suggest that the medial prefrontal cortex (mPFC) is critical for RTM and its development. In both animals and humans DA has been shown to play a crucial role in the development of frontal regions. In the first study, I recorded the spontaneous eyeblink rates (EBR) of 60 preschool aged children (range: 48-62 months) who were also given tasks that assessed their RTM and response-conflict executive functioning (RC-EF) skill. In both animal and human models EBR increases with available DA, and thus EBR can be used as an indirect measure of DA functioning. Regression analyses showed that EBR predicted unique variance in RTM and one Stroop-like measure of RC-EF performance after controlling for the effects of age and language ability. In the second study, I also administered a battery of RTM and RC-EF tasks to 79 preschool aged children (range: 42-54 months). I recorded their spontaneous EBR in addition to collecting genetic material which was processed for allelic variations of DA turnover, transport, and receptor genes. Polymorphisms of catechol-O-methyl transferase gene (COMT) and the dopamine receptor D4 gene (DRD4) were associated with children's RTM performance. These findings provide preliminary evidence that DA functioning is associated with RTM development in the iii preschool years. Results suggest that there may be a selective effect of DA on RTM ability. iv Co-Authorship I assumed the primary responsibility for the conceptualization and execution of the research reported in this thesis. In recognition of her assistance with the original data collection, Lindsay Bowman will appear as a co-author on all manuscripts arising from Chapter Two data. The results presented in Chapter Three are part of a larger study involving the collaboration of Elizabeth Hallinan, and so she will appear as a co-author on all manuscripts from these data. Xudong Liu will also appear as a co-author on Chapter Three manuscripts in recognition of his contribution to processing genetic samples. Lastly, in recognition of his assistance in the data analysis and manuscript …