Generalized arousal has played a key role in a number of theories of emotion over the years (e.g., Duffy, 1941, Lindsley, 1951, Schachter and Singer, 1962, Schachter, 1975, Schildkraut and Kety, 1967, Mandler, 1975, Lang, 1994 and Robbins, 1997) and is also important in contemporary dimensional theories of emotion (Russell, 1980, Russell, 2003 and Russell and Barrett, 1999) and some neural models of emotion (e.g., Davis and Whalen, 2001, Gallagher and Holland, 1994, Kapp et al., 1994 and Lang and Davis, 2006). However, it is important to ask how generalized arousal is triggered in emotional situations, and how the arousal, once present, affects further processing.

Again, the defense circuit is useful for illustrative purposes. The detection of a threat by defense circuits of the amygdala leads selleck chemicals to the activation of central neuromodulatory and peripheral hormonal systems (see Gray, 1993, LeDoux, 1992, LeDoux, 1995, Davis, 1992 and Rodrigues et al., 2009). Thus,

central amygdala outputs target dendritic areas of norpeiphrine, dopamine, serotonin, and acetylcholine containing neurons and cause these to release their chemical products in widespread brain areas (e.g., Reyes et al., 2011, Gray, 1993, Weinberger, 1995 and Kapp et al., check details 1994). Central amygdala outputs also target neurons that activate the sympathetic division of the autonomic nervous system, which releases adrenergic hormones from the adrenal medulla, and the hypothalamic-pituitary-adrenal axis, which releases cortisol from the adrenal cortex (Gray, 1993, Talarovicova et al., 2007, Loewy, 1991 and Reis and LeDoux, 1987). Threats thus not only elicit specific defense responses but also initiate MTMR9 generalized arousal in the brain and body. Body feedback has played an important role in emotion theory for more than a century (James, 1884, Lange, 1885/1922, Schachter and

Singer, 1962, Tomkins, 1962, Adelmann and Zajonc, 1989, Buck, 1980, Damasio, 1994 and Damasio, 1999). One consequence of this pattern of connectivity is that central and peripheral arousal signals facilitate processing in the survival circuit that triggered the activation of arousal. This establishes a loop in which continued activation of the survival circuit by external stimuli produces continued activation of the modulator release, which in turn facilitates the ability of external stimuli to continue to drive the survival circuit. Indeed, modulators facilitate activity in sensory processing areas (e.g., Hurley et al., 2004), which should enhance attention to external stimuli present during survival circuit activation. Modulators also facilitate processing areas involved in retrieving forming, and storing memories (McGaugh, 2003 and Roozendaal et al., 2009).