Infants show rapid, robust learning during a "sensitive period". The classic example of sensitive period learning is imprinting where newly hatched chicks rapidly learn about their mother. Researchers on the present project have a mammalian model of imprinting, where infant rat pups rapidly learn to attach to their mother, that shows pups increase their ability to learn preferences but decrease their ability to learn avoidance. Infant rats learn to prefer their mother's odor, which controls nipple attachment and orientation to the mother. Previous work from this lab has identified unique brain areas used for sensitive period learning. The present project contains experiments designed to explain how the sensitive period ends and adult learning emerges. This is important because special periods of learning occur throughout life in humans and most other species (mother-infant attachment, language acquisition, maternal behavior). This project extends previously funded NSF research that showed increases in corticosterone (CORT, the stress hormone) levels during development terminate the sensitive period. Specifically, high CORT enables brain areas (i.e. amygdala) to participate in learning, which in turn enables pups to learn behaviors such as avoidance required for life outside the nest. Recent work from this lab suggests that sensitive period learning still exists in these older pups but the mother must be present for it to be used. Thus, these older pups appear to have two learning systems available (infant and adult). The experiments in this project will explore the mother's effect on CORT levels and determine how this "switches" between infant learning and adult learning in the brain. This research provides training opportunities for undergraduates and graduates students. The PI is also involved in educational outreach as organizer for the Brain Awareness Week at the Ominplex Science Museum (~4 years), giving science presentations (schools, Scouts, 4H) and began an Intel affiliated Science Fair last year.
