are likely to act in concert with underlying disturbances in other neural circuits that subserve important neuropsychiatric functions, such as motor planning and execution, mood and affect, or attention. The combination of disturbances in these latter circuits with dysfunction in self-regulatory systems may then transform a vulnerability or predisposition for developing an illness into the manifestation of symptoms and functional impairments that constitute an overt disorder. Age-specific vulnerabilities in the maturation of varying components of the neural circuits that mediate these self-regulatory functions are likely to contribute to the differences in age-specific prevalence and characteristic ages of onset of the various disorders described in Chapter 4.

ADHD is a prototypical example of a disorder of self-regulatory control. The largest anatomical studies have suggested that overall brain size is approximately 3 percent smaller in children with ADHD than in healthy children (Castellanos et al., 2002), an abnormality that probably derives from a disproportionate reduction in volume of the inferior prefrontal and anterior temporal cortices bilaterally (Sowell, Thompson, et al., 2003). These anatomical disturbances are consistent with the self-regulatory deficits that manifest as the hyperactivity, distractibility, and impulsivity of children with ADHD. Additional anatomical and functional disturbances involve the basal ganglia, the subcortical portions of the frontostriatal circuits that subserve self-regulatory control (Plessen and Peterson, 2008; Shafritz, Marchione, et al., 2004; Vaidya et al., 1998). Anatomical and functional disturbances in these regulatory control systems, though in different portions and subsystems than in ADHD, have also been reported in bipolar disorder (Blumberg, Leung, et al., 2003; Blumberg, Martin, et al., 2003), Tourette syndrome (Marsh, Zhu, et al., 2007; Peterson et al., 2001), obsessive compulsive disorder (Rosenberg and Keshavan, 1998), and eating disorders (Marsh, Gerber, et al., 2009).

Cognitive reappraisal already is a prominent component of the cognitive-behavioral therapies commonly used in the treatment of depression and anxiety disorders. Self-regulatory control tasks are being developed to treat various forms of psychopathology, including tic disorders and ADHD (Posner, 2005; Rueda, Rothbart, et al., 2005; Tang, Ma, et al., 2007; Woods, Himle, et al., 2008). Whether these interventions hold promise as prevention strategies is unknown.

Compensatory and Neuromodulatory Systems

Compensatory responses are attempts to correct for disturbances else-where in a biological system and to reestablish a biological balance, known as homeostasis. The quintessential purpose of the brain is to strive to achieve and to maintain homeostasis, both in its internal operations and

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