9604299 Striedter The ability to learn complex vocalizations has evolved only in humans, songbirds, and parrots. This project investigates how the neural circuits controlling vocalization have changed during the evolution of vocal learning. Particular emphasis is placed on an area of the midbrain, as the function of this region is hypothesized to have changed significantly as the capacity for vocal behavior moves from being genetically coded to being dependent on learning. Neuroanatomical analysis of the inputs and outputs of this area, observations of the behavioral effects of damage to this area, and electrophysiological examination of the activity of midbrain neurons are all used to test comparative analysis is then used to reconstruct how neural circuitry and behavioral function of the vocal control system change during evolution. In doing so, this is one of the first studies to examine how historical constraints can influence current brain function. The results of this study enhance our understanding of the brain's systems for controlling vocal behavior, including human speech, as well as improve our understanding of how nervous systems in general evolve to accomodate complex new behavioral abilities within the constraints of preexisting circuits with preexisting functions. Such research is important in advancing knowledge about how natural and artificial learning systems acquire increasingly complex abilities as a function of experience.
