28 Chapter 2 (i.e., obtaining social reward but also avoiding punishment; see Delgado, (2009), behavioral activation, and motivational behavior (Cools, 2008; Yacubian & Büchel, 2009). The anterior prefrontal cortex plays a crucial role in the cognitive control network as it is involved in the regulation of emotion (Damásio, 1994; Rolls, 1999). It also has a role in social motivational behavior as it inhibits the amygdala, making it possible to control and override automatic behavioral approach and avoidance tendencies (Roelofs, Minelli, et al., 2009; Volman, Roelofs, Koch, Verhagen, & Toni, 2011). Furthermore, it modulates mesolimbic striatal activity (Grace, Floresco, Goto, & Lodge, 2007; Wager, Davidson, Hughes, Lindquist, & Ochsner, 2008). Naturally, this description is a highly simplified one, and many other brain regions partake in these networks (Cremers & Roelofs, 2016). Hormonal regulation of social motivational behavior Testosterone The hypothalamus–pituitary–gonadal (HPG) axis with its end product testosterone plays a key role in the neuroendocrine regulation of social motivational behavior in both sexes. Testosterone levels follow a pulsatile, seasonal, and diurnal cycle in which levels are highest upon waking and typically decline by 50% during the day (Dabbs, 1990). Gonadotropin-releasing hormone (GnRH) is secreted from the hypothalamus, which stimulates the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary gland, which in turn triggers production of testosterone and estradiol in the gonads (i.e., testes and ovaries). The secreted estradiol and testosterone in turn inhibit the hypothalamus and pituitary, thus forming a negative feedback loop. In addition, small amounts of testosterone are produced in the adrenal cortex and synthesized in the brain from cholesterol and other steroid precursors. Testosterone is able to cross the blood–brain barrier, and besides having (epigenetic) organizational effects on brain structures during pre- and early postnatal development, testosterone also influences emotion, motivation, and behavior later in life (i.e., activational effects; Lombardo et al. (2012; McHendry, Carrier, Hull, & Kabbaj. (2014). Actions of testosterone are brought about directly via androgen receptors but also via metabolites such as estradiol, dihydrotestosterone, and 3-diol, which binds to the aminobutyric acid (GABA-A) receptor (Balthazart & Ball, 2006; Wood, 2008). The effects can either be slow and long-lasting (i.e., hours–days) via a genomic pathway featuring intracellular steroid receptors, or rapid (i.e., seconds–minutes) via membrane-bound (steroid) receptors, which exert non-genomic actions in the cell. Importantly, testosterone acts through a steroid-responsive network which includes the amygdala, hypothalamus,
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