Mechanisms for Terminating a Neonatal Learning Sensitive Period.

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

Altricial species, such as humans and rats, have a difficult task at birth: they must be able to identify, remember and prefer their caretaker. This attachment is greatly dependent upon perinatal experiences, especially learning. For example, human infants learn their mother's voices, faces and odors; rat pups learn their mother's odor, and avian species learn to identify the mother visually and/or aurally. Generally, infants that require perinatal learning for attachment exhibit unique learning abilities that have been referred to as imprinting, or sensitive period or critical period learning. One consistent aspect of early attachment is that the organism appears to have a very broad basis for learning an attachment which involves increased ability to acquire approach responses and a decreased ability to acquire aversions (Bowlby, 1965). These unique infant learning capabilities, which facilitate attachment, appear throughout the animal kingdom and may have evolved to ensure that altricial animals easily form a repertoire of proximity-seeking behaviors, regardless of the specific qualities of the treatment they receive from the primary caretaker. However, the sensitive periods for attachment must end as animals matures and must learn about the environment away from the nest. They must now be able to learn to acquire approach responses only to special stimuli and learn to avoid other stimuli. The research proposed in this grant will explore the neural mechanisms which help an organism make the transition from one stage of development to the next. While there is some understanding of the neural mechanisms that underlie the sensitive period, there is very little known about what neural mechanisms cause the sensitive period to end and begin the next stage of the animal's life. The results of the experiments proposed here will begin to characterize those physiological events that are involved in the termination of a sensitive period and the emergence of neural structures for the next stage of development. Recent work from this laboratory suggests that corticosterone (a neurohormone involved in stress and other behaviors) plays a critical role in the termination of the infant's unique learning abilities. Experiments have been proposed that further characterize the role of corticosterone in the termination of the sensitive period and assess the actions of corticosterone on brain areas important in learning: the amygdala, hippocampus and locus coeruleus.