PROJECT SUMMARY Early experiences lay the groundwork for later learning and have long-lasting impacts on cognitive development. Yet, contextual memories acquired before the age of four – despite being clearly encoded and retained over shorter durations – are notoriously absent in older children and adults. If we assume that all early memories are encoded equally well, this is clearly a paradox, but the encoding context likely influences memory formation/retention. In fact, given that caregivers are a highly salient stimulus and modulate young children's arousal, they may provide a context that enhances memory. To assess the functions of early memory systems and their modulation by the caregiver, we investigate item-context memory in toddlerhood using behavior, pupillometry via eye-tracking, and fMRI. My background in conducting awake infant/toddler fMRI, including during memory tasks, makes me well-suited to successfully complete this task with the guidance and mentorship of the sponsor and co-sponsor. The sponsor is a leading expert in developmental affective neuroscience and the role of early caregiving experiences in development, and the co-sponsor is a leading expert in neurobehavioral research on attention, learning, and memory in early life (including via pupillometry). They will support my training goals of: (1) acquiring discipline-specific background and applied methods to investigate early caregiving as a developmental context, (1) applying principles grounded in developmental science to strengthen methodological skills for behavioral assessment of children, (3) learning pupillometry methods with toddlers, and (4) professional development. For the proposed project, the first aim is to examine how a novel context associated with the caregiver modulates toddlers' arousal. We hypothesize that arousal (operationalized as increased pupil size) will be greater for contexts associated with the caregiver vs. a familiar other (teacher). The second aim is to evaluate and examine how a context associated with the caregiver modulates memory behavior. Prior work has shown that learning and memory systems (e.g., hippocampus, amygdala, and medial prefrontal cortex) are sensitive to social contexts, particularly when the social context is that of the caregiver. Thus, we predict that toddlers' item-context memory will be enhanced when encoding occurs in the caregiver-associated (vs. teacher-associated) context. Furthermore, we predict this effect may be mediated by toddlers' arousal during encoding. Finally, as an exploratory aim, we will examine how the caregiver-as-context influences neural mechanisms of item-context memory in awake toddlers. Prior work in rodents has shown that the hippocampus can encode item-context memories early in life, but this has not been tested in humans given the difficulty of conducting awake fMRI with young children. We hypothesize that the hippocampus will be more engaged during the encoding of item-context pairs that tod...