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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"This result was consistent with a previous study using a similar brain measurement (functional connectivity density) which indicated lower connectivity, especially long-range connectivity, in superior parietal cortex in children with ADHD in a large database (Tomasi & Volkow, 2012). Task-based fMRI studies also identified reduced neural activity in parietal cortex and lower functional connectivity between parietal cortex and other brain regions in ADHD (Cao et al., 2008; Tamm, Menon, & Reiss, 2006; Vance et al., 2007; Vloet et al., 2010). Considering that the parietal cortex (i.e., the superior parietal cortex ) is an important area involved in the dorsal attentional network (Tomasi & Volkow, 2011), the decreased connectivity between this area with other brain regions found in this study may be associated with the deficits of attention in ADHD. "
[Show abstract][Hide abstract]ABSTRACT: Cognitive-behavioral therapy (CBT) is an efficacious psychological treatment for adults with attention-deficit/hyperactivity disorder (ADHD), but the neural processes underlying the benefits of CBT are not well understood. This study aims to unravel psychosocial mechanisms for treatment ADHD by exploring the effects of CBT on functional brain networks. Ten adults with ADHD were enrolled and resting-state functional magnetic resonance imaging scans were acquired before and after a 12-session CBT. Twelve age- and gender-matched healthy controls were also scanned. We constructed whole-brain functional connectivity networks using graph-theory approaches and further computed the changes of regional functional connectivity strength (rFCS) between pre- and post-CBT in ADHD for measuring the effects of CBT. The results showed that rFCS was increased in the fronto-parietal network and cerebellum, the brain regions that were most often affected by medication, in adults with ADHD following CBT. Furthermore, the enhanced functional coupling between bilateral superior parietal gyrus was positively correlated with the improvement of ADHD symptoms following CBT. Together, these findings provide evidence that CBT can selectively modulate the intrinsic network connectivity in the fronto-parietal network and cerebellum and suggest that the CBT may share common brain mechanism with the pharmacology in adults with ADHD.
Full-text · Article · Nov 2015 · Behaviour Research and Therapy
"No differences between groups in either γ, λ, σ or global efficiency and clustering. increasingly implicated in ADHD (Aboitiz et al., 2014), responsible for attentional shifts and detection of specific or salient stimuli (Tamm et al., 2006). Our results also indicated greater local efficiency and clustering in adults with ADHD. "
[Show abstract][Hide abstract]ABSTRACT: Prior studies demonstrate altered organisation of functional brain networks in attentiondeficit/hyperactivity
disorder (ADHD). However, the structural underpinnings of these
functional disturbances are poorly understood. In the current study, we applied a graphtheoretic
approach to whole-brain diffusion magnetic resonance imaging data to investigate
the organisation of structural brain networks in adults with ADHD and unaffected controls
using deterministic fibre tractography. Groups did not differ in terms of global network
metrics - small-worldness, global efficiency and clustering coefficient. However, there were
widespread ADHD-related effects at the nodal level in relation to local efficiency and
clustering. The affected nodes included superior occipital, supramarginal, superior temporal,
inferior parietal, angular and inferior frontal gyri, as well as putamen, thalamus and posterior
cerebellum. Lower local efficiency of left superior temporal and supramarginal gyri was
associated with higher ADHD symptom scores. Also greater local clustering of right putamen
and lower local clustering of left supramarginal gyrus correlated with ADHD symptom
severity. Overall, the findings indicate preserved global but altered local network organisation
in adult ADHD implicating regions underpinning putative ADHD-related neuropsychological
Full-text · Article · Oct 2015 · Clinical neuroimaging
"In addition, the parietal lobe is related to attention, memory, and cognitive process. Different brain activations in the parietal lobe for ADHD patients have been reported in the literature (Tamm, Menon, and Reiss (2006)). Interestingly, functional relationship between the insula and cingulate gyrus has received a lot of attention in the literature (Taylor, Seminowicz , and Davis (2009); Medford and Critchley (2010)). "
[Show abstract][Hide abstract]ABSTRACT: In spatial-temporal neuroimaging studies, there is an evolving literature on the analysis of functional imaging data in order to learn the intrinsic functional connectivity patterns among different brain regions. However, there are only few efficient approaches for integrating functional connectivity pattern across subjects, while accounting for spatial-temporal functional variation across multiple groups of subjects. The objective of this paper is to develop a new sparse reduced rank (SRR) modeling framework for carrying out functional connectivity analysis across multiple groups of subjects in the frequency domain. Our new framework not only can extract both frequency and spatial factors across subjects, but also imposes sparse constraints on the frequency factors. It thus leads to the identification of important frequencies with high power spectra. In addition, we propose two novel adaptive criteria for automatic selection of sparsity level and model rank. Using simulated data, we demonstrate that SRR outperforms several existing methods. Finally, we apply SRR to detect group differences between controls and two subtypes of attention deficit hyperactivity disorder (ADHD) patients, through analyzing the ADHD-200 data.