This paper is a preliminary investigation of whether adolescents with severe substance and conduct problems (SCP) exhibit atypical patterns of neural activation when they must exert internal control over their behavior in the face of salient distracting information. Among adolescents, substance dependence (SD) and conduct disorder (CD) are often comorbid with vulnerability thought to arise from shared or similar genetic mechanisms (Hicks et al. 2004
). Both are associated with “disinhibitory psychopathology” (McGue et al., 2001; van den Bree et al., 1998
), including a disregulation of adaptive self-control in the face of strong environmental cues or previous experience (Filmore and Rush, 2002
). Experimentally, such disregulation in adults is associated with poor performance on the Stroop task (Mintzer and Stitzer, 2002
; Simon et al., 2000
), a classic measure of attentional control (MacLeod, 1992
). In this task, individuals identify a word’s ink color, while ignoring the word’s meaning. Strong internal control over behavior is required to attend to the ink color and override the more automatic process of reading the word, especially when the word and ink color conflict (e.g., the word “red” in blue ink).
The far less extensive research on attentional control in adolescents with substance problems also suggests that attentional control is compromised (Giancola, et al., 1998
), while the data regarding conduct disorder alone are mixed (Bauer and Hesselbrock, 1999 Herba, Tranah, Rubia & Yule, 2006
; Oosterlaan et al., 2005
). More specifically, poorer attentional abilities, low constructive thinking and high antisocial behavior predict substance use disorders in 14–18 year old adolescent females (Aytaclar et al. 1999
; Giancola, et al., 2001
, Tapert & Brown, 1999
; Tapert et al. 2002
The neural bases of these attentional deficits have been relatively unexplored. The few studies examining patterns of brain activation in adolescents with substance use disorder have focused more on memory than attention. In two pilot studies, one with 7 adolescent cannabis users (Jacobsen et al., 2004a
) and another with 6 adolescent users of ecstasy (Jacobsen et al., 2004b
), greater hippocampal activation relative to a fixation baseline was observed in the substance users than controls. Separately, teens with alcohol use disorders performing a working memory task exhibit greater activation in bilateral posterior parietal cortex and less activation in precuneus and posterior cingulate regions than controls (Tapert et al., 2004
). Additional differences in prefrontal regions are observed when alcohol use disorder is comorbid with marijuana use disorder (Schweinsburg et al., 2005
) and effects are more pronounced in females than males (Caldwell et al., 2005
). Hence, although atypical brain activation is observed in adolescents with substance use disorders, no clear consistent pattern has yet emerged. Moreover, to our knowledge, no imaging studies have been performed on attentional abilities in adolescents with or comorbid for conduct disorder.
In the current study we examine the neural bases of deficits in attentional control in adolescents with severe SCP using functional magnetic resonance imaging (fMRI) and the color-word Stroop task. We use this task because our extensive prior fMRI research with this task (Banich et al., 2000a
, Milham et al. 2001
; Milham and Banich, 2005
; Liu et al., 2004
) has shown that our procedures are sensitive to detecting the neural substrates of attentional control as well as to group differences in such substrates (Milham et al., 2002
). Moreover, this task has yielded differences between adults with and without substance use disorder (Gruber and Yurgelun-Todd, 2005
). In that study, two effects were observed in regions typically linked to attentional control. First, the 9 adult, heavy users of cannabis activated mid-cingulate regions for the incongruent Stroop condition (the word “red” displayed in blue ink) relative to a fixation baseline, whereas the 10 non-smoking controls activated more rostral regions of the cingulate. Second, while the dorsolateral prefrontal activity of marijuana users was diffuse and bilateral, that of the controls was more focal and right-sided.
The group of adolescents we examined is characterized by poly-substance abuse as well as co-morbidity with other psychiatric disorders, most notably conduct disorder. This sample clearly cannot be considered a “pure” homogenous group for the purposes of certain research questions (e.g., “Do different drugs of abuse have differential effects on the neural substrates of attentional control in the adolescent brain?”). Nonetheless, the sample recruited very well characterizes the type of adolescent patient we typically treat in our clinical program. As such, the results may provide insight into alterations of neural functioning in such a severely affected group.