Parietal Attentional System Aberrations During Target Detection in Adolescents With Attention Deficit Hyperactivity Disorder: Event-Related fMRI Evidence

Stanford University, Palo Alto, California, United States
American Journal of Psychiatry (Impact Factor: 12.3). 07/2006; 163(6):1033-43. DOI: 10.1176/appi.ajp.163.6.1033
Source: PubMed


Directed attention, the ability to allocate and direct attention toward a salient stimulus, is impaired in attention deficit hyperactivity disorder (ADHD). This construct is often assessed with target detection or oddball tasks, and individuals with ADHD perform poorly on such tasks. However, to date, the specific brain structures or neural mechanisms underlying target detection dysfunction in individuals with ADHD have not been identified. The authors' goal was to investigate neural correlates of target detection dysfunction in ADHD using event-related fMRI.
Behavioral and brain activation data were collected while subjects performed a visual oddball task. Participants included 14 right-handed male adolescents with ADHD (combined type) and 12 typically developing age- and handedness-matched male comparison subjects.
Individuals with ADHD made significantly more errors of commission than comparison subjects. Further, relative to comparison subjects, individuals with ADHD showed significantly less activation in the bilateral parietal lobes (including the superior parietal gyrus and supramarginal and angular gyri of the inferior parietal lobe), right precuneus, and thalamus.
Adolescents with ADHD demonstrated significant impairments in their ability to direct and allocate attentional resources. These difficulties were associated with significant aberrations in the parietal attentional system, which is known to play a significant role in attention shifting and detecting specific or salient targets. Thus, dysfunction in the parietal attentional system may play a significant role in the behavioral phenotype of ADHD.

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    • "Thus, only neural activity associated with correct task performance was extracted which might be similar in children and adolescents with and without ADHD. Alternatively, the more appealing stimulus material of landscape scenes compared to letters [Tamm et al., 2006], arrows [Rubia et al., 2007], or sine tones [Stevens et al., 2007] as well as the required button press for every picture could have improved the performance of participants with ADHD. It has been shown, that ADHD patients are able to show unimpaired performance when a task is more intriguing or when the frequency of target stimuli is high [Corkum and Siegel, 1993; Friedman-Hill, 2010]. "
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    ABSTRACT: Attentional problems in patients with attention deficit hyperactivity disorder (ADHD) have often been linked with deficits in cognitive control. Whether these deficits are associated with increased sensitivity to external salient stimuli remains unclear. To address this issue, we acquired functional brain images (fMRI) in 38 boys with and without ADHD (age: 11–16 years). To differentiate the effects of item novelty, contextual rareness and task relevance, participants performed a visual oddball task including four stimulus categories: a frequent standard picture (62.5%), unique novel pictures (12.5%), one repeated rare picture (12.5%), and a target picture (12.5%) that required a specific motor response. As a main finding, we can show considerable overlap in novelty-related BOLD responses between both groups, but only healthy participants showed neural deactivation in temporal as well as frontal regions in response to novel pictures. Furthermore, only ADHD patients, but not healthy controls, engaged wide parts of the novelty network when processing the rare but familiar picture. Our results provide first evidence that ADHD patients show enhanced neural activity in response to novel but behaviorally irrelevant stimuli as well as reduced habituation to familiar items. These findings suggest an inefficient use of neuronal resources in children with ADHD that could be closely linked to increased distractibility. Hum Brain Mapp, 2015. © 2014 Wiley Periodicals, Inc.
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    • "Third, an important role for the parietal lobe in ADHD has recently emerged from brain imaging studies. Thus, for example, a number of structural and functional imaging studies have shown prominent abnormalities in right parietal areas (Konrad et al, 2006; Silk et al, 2005; Smith et al, 2006; Sowell et al, 2003; Tamm et al, 2006). Reduced cortical thickness within the right parietal lobe has been reported in children and adults with ADHD (Makris et al, 2007). "

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    • "). Decreased activation in the right-SPL in ADHD patients has also been observed in several studies of response inhibition and attention (Booth et al., 2005; Tamm et al., 2006). Decreased IFG activation has been a consistent fMRI finding in ADHD for various executive functions (Epstein et al., 2007). "
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