Contrary to assumptions that changes in brain networks are possible only during crucial periods of development, research in the past decade has supported the idea of a permanently plastic brain. Novel experience, altered afferent input due to environmental changes and learning new skills are now recognized as modulators of brain function and underlying neuroanatomic circuitry. Given findings in experiments with animals and the recent discovery of increases in gray and white matter in the adult human brain as a result of (...) learning, the old concept of cognitive reserve, that is the ability to reinforce brain volume in crucial areas and thus provide a greater threshold for age-dependent deficits, has been reinforced. The challenge we face is to unravel the exact nature of the dynamic structural alterations and, ultimately, to be able to use this knowledge for disease management. Understanding normative changes in brain structure that occur as a result of environmental changes and demands is pivotal to understanding the characteristic ability of the brain to adapt. (shrink)

In this paper we provide a critical review of research concerned with social/environmental mechanisms that modulate human neuroendocrine function. We survey research in four behavioral systems that have been shaped through evolution: competition, partnering, sex, and pregnancy/parenting. Generally, behavioral neuroendocrine research examines how hormones affect behavior. Instead, we focus on approaches that emphasize the effects of behavioral states on hormones (i.e., the “reverse relationship”), and their functional significance. We focus on androgens and estrogens because of their relevance to sexually selected (...) traits. We conclude that the body of research employing a reversed or bidirectional perspective has an incomplete foundation: participants are mainly heterosexual men, and the functionality of induced shifts in neuroendocrine factors is generally unknown. This area of research is in its infancy, and opportunities abound for developing and testing intriguing research questions. (shrink)