Sensitive periods in affective development: nonlinear maturation of fear learning

Abstract

At specific maturational stages, neural circuits enter sensitive periods of heightened plasticity, during which the development of both brain and behavior are highly receptive to particular experiential information. A relatively advanced understanding of the regulatory mechanisms governing the initiation, closure, and reinstatement of sensitive period plasticity has emerged from extensive research examining the development of the visual system. In this article, we discuss a large body of work characterizing the pronounced nonlinear changes in fear learning and extinction that occur from childhood through adulthood, and their underlying neural substrates. We draw upon the model of sensitive period regulation within the visual system, and present burgeoning evidence suggesting that parallel mechanisms may regulate the qualitative changes in fear learning across development.

Figure 1

Developmental regulation of fear-related plasticity and behavior. (Top) Inhibitory neurotransmission peaks early within the amygdala, whereas increases in the prefrontal cortex begin during adolescence and do not peak until adulthood. Gonadal hormones and BDNF levels peak during adolescence. Myelination increases gradually from childhood to adulthood. (Bottom) Fear learning, extinction, and reconsolidation exhibit qualitative maturational changes across the lifespan. Cued and contextual fear learning emerge during childhood, but the memories are labile. Contextual fear expression and extinction learning are attenuated during adolescence. In adulthood, extinguished fear recovers, but can be attenuated persistently through reconsolidation.