Meta-Analysis of Structural Imaging Findings in Attention-Deficit/Hyperactivity Disorder

Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Biological Psychiatry (Impact Factor: 10.26). 06/2007; 61(12):1361-9. DOI: 10.1016/j.biopsych.2006.06.011
Source: PubMed


Although there are many structural neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) in children, there are inconsistencies across studies and no consensus regarding which brain regions show the most robust area or volumetric reductions relative to control subjects. Our goal was to statistically analyze structural imaging data via a meta-analysis to help resolve these issues.
We searched the MEDLINE and PsycINFO databases through January 2005. Studies must have been written in English, used magnetic resonance imaging, and presented the means and standard deviations of regions assessed. Data were extracted by one of the authors and verified independently by another author.
Analyses were performed using STATA with metan, metabias, and metainf programs. A meta-analysis including all regions across all studies indicated global reductions for ADHD subjects compared with control subjects, standardized mean difference=.408, p<.001. Regions most frequently assessed and showing the largest differences included cerebellar regions, the splenium of the corpus callosum, total and right cerebral volume, and right caudate. Several frontal regions assessed in only two studies also showed large significant differences.
This meta-analysis provides a quantitative analysis of neuroanatomical abnormalities in ADHD and information that can be used to guide future studies.

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    • "It has been proposed that the cerebellum is involved in the time dependent perception of a delayed reward (Rubia et al. 2009). Additionally, a meta-analysis of structural MRI studies in ADHD has shown abnormal cerebellar structure with the largest differences observed in the right lobe (Valera et al. 2007). An altered perception of time in the context of a delayed reward is a potential mechanism for more impulsive discounting. "
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    ABSTRACT: An important characteristic of childhood attention-deficit/hyperactivity disorder (ADHD) is a bias towards small immediate versus larger delayed rewards, but it is not known if this symptom is also a feature of adult ADHD. A delay-discounting task was administered to participants with adult ADHD and a comparison group in conjunction with functional magnetic resonance imaging. Participants responded to a series of questions that required judgments between small sums of money available immediately and larger sums obtained after a temporal delay. Question parameters were adjusted by an adaptive algorithm designed to converge on each participant’s discounting indifference point, an individual set point at which there is equal valuation of both choices. In all participants, robust task activation was observed in regions previously identified in functional imaging studies of delay discounting. However, adults with ADHD showed less task activation in a number of regions including the dorsolateral prefrontal cortex, superior frontal gyrus, anterior cingulate, caudate nucleus and declive of the cerebellum. Additionally, the degree to which a participant discounted delayed rewards was inversely related to task activation in the cerebellum. The results suggest that the bias towards immediate rewards in childhood ADHD may not persist behaviorally, but instead present in adulthood as alterations in frontostriatal and frontocerebellar networks.
    Acta neurobiologiae experimentalis 10/2015; 75(3):2015. · 1.29 Impact Factor
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    • "Moreover, there is evidence that abnormal brain lateralization might be a core component underlying dysfunctions in ADHD (Hale et al., 2008, 2009). At the structural and neuroimaging level, studies have reported atypical right hemisphere structure (Valera et al., 2007; Frodl and Skokauskas, 2012); in particular, smaller size of right frontal and prefrontal cortex were found in subjects with ADHD (Hill et al., 2003; Almeida et al., 2010). Atypical right hemisphere structure may affect attentional processing and response inhibition (Stefanatos and Wasserstein, 2001; Hart et al., 2013). "
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    ABSTRACT: Many clinical studies reported a compromised brain lateralization in patients with Attention-Deficit/Hyperactivity Disorder (ADHD) without being conclusive about whether the deficit existed in the left or right hemisphere. It is well-recognized that studying ADHD dimensionally is more controlled for comorbid problems and medication effects, and provides more accurate assessment of the symptoms. Therefore, the present study applied the dimensional approach to test the relationship between brain lateralization and self-reported ADHD symptoms in a population sample. Eighty-five right-handed university students filled in the Conners’ Adult ADHD Rating Scales and performed a lateralization reaction time task. The task consists of two matching conditions: one condition requires nominal identification for letters tapping left hemisphere specialization (Letter Name-Identity condition) and the other one requires physical and visuospatial identification for shapes tapping right hemisphere specialization (Shape Physical-Identity condition). The letters or shapes to be matched are presented in left or right visual field of a fixation cross. For both task conditions, brain lateralization was indexed as the difference in mean reaction time between left and right visual field. Linear regression analyses, controlled for mood symptoms reported by a depression, anxiety and stress scale, showed no relationship between the variables. These findings from a population sample of adults do not support the dimensionality of lateralized information processing deficit in ADHD symptomatology. However, group comparison analyses showed that subjects with high level of inattention symptoms close to or above the clinical cut-off had a reduced right hemisphere processing in the Shape Physical-Identity condition.
    Frontiers in Psychology 09/2015; 6(1418). DOI:10.3389/fpsyg.2015.01418 · 2.80 Impact Factor
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    • "Finally, in one previous study restricted to female participants, Castellanos et al. (2001) found no significant differences between girls with ADHD and TD girls when measuring the volumes of the caudate nucleus, globus pallidus, frontal lobe (total volume)) and cerebellum, while girls with ADHD exhibited decreased grey matter volumes of the posterior inferior lobule in the cerebellar vermis when compared to TD girls (Castellanos et al., 2001). This limited number of studies suggest that girls with ADHD may not exhibit the structural abnormalities of the basal ganglia consistently reported in predominantly male ADHD samples (Valera et al., 2007; Nakao et al., 2011; Frodl and Skokauskas, 2012). "
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    ABSTRACT: Female participants have been underrepresented in previous structural magnetic resonance imaging reports on attention-deficit/hyperactivity disorder (ADHD). In this study, we used optimized voxel-based morphometry to examine grey matter volumes in a sample of 33 never-medicated children with combined-type ADHD and 27 typically developing (TD) children. We found a gender-by-diagnosis interaction effect in the ventral anterior cingulate cortex (ACC), whereby boys with ADHD exhibited reduced volumes compared with TD boys, while girls with ADHD showed increased volumes when compared with TD girls. Considering the key role played by the ventral ACC in emotional regulation, we discuss the potential contribution of these alterations to gender-specific symptoms' profiles in ADHD. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
    Developmental Cognitive Neuroscience 06/2015; 11. DOI:10.1016/j.dcn.2015.06.001 · 3.83 Impact Factor
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