Developmental trajectories during adolescence in males and females: a cross-species understanding of underlying brain changes

Abstract

Adolescence is a transitional period between childhood and adulthood that encompasses vast changes within brain systems that parallel some, but not all, behavioral changes. Elevations in emotional reactivity and reward processing follow an inverted U shape in terms of onset and remission, with the peak occurring during adolescence. However, cognitive processing follows a more linear course of development. This review will focus on changes within key structures and will highlight the relationships between brain changes and behavior, with evidence spanning from functional magnetic resonance imaging (fMRI) in humans to molecular studies of receptor and signaling factors in animals. Adolescent changes in neuronal substrates will be used to understand how typical and atypical behaviors arise during adolescence. We draw upon clinical and preclinical studies to provide a neural framework for defining adolescence and its role in the transition to adulthood.

Figure 1

Timeline of developmental processes across humans and rodents. Pink bars represent the timeline for females, which precedes that of males, represented in blue bars. Transient expression of receptors (“ectopic”) occurs early in life and expression is no longer observed later in life. Ectopic expression differs from continued receptor expression within other brain regions.

Figure 2

a) Drawings of cortical lamination in vertical cross-section by Santiago Ramon y Cajal following Nissl (left, middle) in an adult and Golgi staining (right) in a 1½ month old infant. B) patterns of synaptic changes that occur during the transitions between childhood and adulthood in Layers I (the molecular layer), III (the external pyramidal layer; predominantly corticocortical efferents), and V (the internal pyramidal layer V; predominantly subcortical efferents).