Functional and Structural MRI Studies on Impulsiveness: Attention-Deficit/Hyperactive Disorder and Borderline Personality Disorders

Impulsive behavior is characterized a tendency to initiate behavior without sufficient/adequate consideration of consequences. It typically refers to ill-conceived, premature or inappropriate behavior that may be self-destructive or harmful to other individuals (Chamberlain and Sahakian, 2007). Pathological impulsiveness is associated with impaired performance on neuropsychological tests of attention and executive function and with neuroimaging evidence for structural and/or functional correlates, particular in frontal lobe regions (Congdon and Canli, 2005; Crews and Boettiger, 2009; Rubia et al., 2007). Impulsive behavior is a major component of several neuropsychiatric disorders, including schizophrenia, ADHD, substance abuse, bipolar disorder, and borderline and antisocial personality disorders. The notion of impulsiveness incorporates a multidimensional construct consisting of a range of inter-related factors including noveltyseeking and reckless behavior, lack of planning ability and self-control whereby mechanistic relations evolve from its role in initiating action (Barratt and Patton, 1983; Moeller et al., 2001). The construct incorporates motor impulsiveness, inability to tolerate delays, lack of planning and an incapacity for self-control. Impulsiveness, with or without aggressiveness, has been associated with a range of personality disorders and other psychopathologies (Haden and Shiva, 2008; Krishnan-Sarin et al., 2007; Palomo et al., 2007a; Reynolds, 2006; Shiva et al., 2009), with impulse control difficulties often of primary diagnostic importance (e.g., Pfefferbaum & Wood, 1994; Quirk and McCormick, 1998). A variety of linear regression analyses based upon several selfreport questionnaire studies including a range of cognitive-emotional personal attributes have indicated that impulsiveness is predicted by negative affect, amotivation and depressiveness and counterpredicted by positive affect and internal locus of control in healthy volunteers (Palomo et al., 2008a, b; but see also Miller et al., 2009). Cyders et al. have discussed the influence of positive urgency, acting rashly under extreme positive affect, and negative urgency as central risk factors for impulsive and maladaptive behavior (see also Cyders and Smith, 2008a, b; Cyders et al., 2009, 2010; Zapolsky et al., 2009).