Sarah W. Bottjer Professor Neurobiology, Biological Sciences College of Letters Arts & Sciences

Education:
BA 1975 Psychology - State University of New York, Binghamton, NY
PhD 1979 Psychology - Indiana University, Bloomington, IN

Postdoctoral Research Fellowship:
1980 - 1986 University of California, Los Angeles

Started at USC: 1986

Research Topics: Learning & Memory, Cell Death, Developmental Biology, Cellular Neurobiology

Research Description

The major goal of our lab is to understand relationships between development and learning at the level of both brain and behavior. We perform experiments at cellular and systems levels of analysis using the neural circuits that underlie vocal learning in songbirds as a model system. We are studying neuronal survival versus neurodegeneration, morphological changes in dendritic and axonal arbors, and changes in synaptic plasticity that influence functional patterns of connectivity between neurons. A major goal is to determine how experience regulates these processes to attain mature neural circuits that encode a complex learned behavior.

Why is this interesting and important? Development in animals is frequently characterized by periods of heightened capacity for both neural and behavioral change. Sensitive periods of development are those in which brain and behavior are most susceptible to modification by experiential factors in the external environment and/or changes in internal milieu (such as levels of hormones and growth factors). Certain types of learning occur only during sensitive periods of development, and coincide with heightened phases of neural plasticity. In humans, for example, children are much more adept at learning languages than are adults, and the time at which the capacity for language acquisition decreases seems to correlate with the end of the period of maturation of the cerebral hemispheres.

One of the few groups of organisms other than humans that learn vocal sounds used for communication during a sensitive period of development are songbirds. Vocal learning in songbirds, as in humans, is highly developmentally regulated - a specific vocal pattern emerges gradually during development as juvenile birds listen to and learn to copy a “tutor” song. Song learning and production are controlled by circuits of highly localized, interconnected brain nuclei, including regions of cortex and basal ganglia. This brain-behavior system provides an ideal model in which to address basic questions pertaining to relationships between neural development and complex processes of learning and behavior.

In summary, our goal is to elucidate mechanisms that regulate basic processes of neural development, and in so doing to shed light on factors governing the emergence of a learned behavior. On-going experiments include the role of neurotrophic growth factors in preventing neurodegeneration so as to sculpt circuits for vocal learning, the influence of sensory experience in regulating morphology of axons and the specificity of their connections, and changes in synaptic strength in vocal-control circuits during learning that are induced by changes in neural activity and the expression of specific molecules such as NMDA receptors. These studies are yielding basic information regarding fundamental mechanisms of neural development. The results are therefore highly relevant to questions of normal brain function, especially the enhanced learning capacity of juvenile brains, as well as to the brain’s response to injury, disease and aging.