Topological organization of the "small-world" visual attention network in children with attention deficit/hyperactivity disorder (ADHD).

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed childhood psychiatric disorder. Disrupted sustained attention is one of the most significant behavioral impairments in this disorder. We mapped systems-level topological properties of the neural network responsible for sustained attention during a visual sustained task, on the premise that strong associations between anomalies in network features and clinical measures of ADHD would emerge. METHODS: Graph theoretic techniques (GTT) and bivariate network-based statistics (NBS) were applied to fMRI data from 22 children with ADHD combined-type and 22 age-matched neurotypicals, to evaluate the topological and nodal-pairing features in the functional brain networks. Correlation testing for relationships between network properties and clinical measures were then performed. RESULTS: The visual attention network showed significantly reduced local-efficiency and nodal-efficiency in frontal and occipital regions in ADHD. Measures of degree and between-centrality pointed to hyper-functioning in anterior cingulate cortex and hypo-functioning in orbito-frontal, middle-occipital, superior-temporal, supra-central, and supra-marginal gyri in ADHD. NBS demonstrated significantly reduced pair-wise connectivity in an inner-network, encompassing right parietal and temporal lobes and left occipital lobe, in the ADHD group. CONCLUSIONS: These data suggest that atypical topological features of the visual attention network contribute to classic ADHD symptomatology, and may underlie the inattentiveness and hyperactivity/impulsivity that are characteristics of this syndrome.

Speaking from ignorance: not agreeing with others we believe are correct.

Values-pragmatics theory (Hodges & Geyer, 2006) predicts that people will sometimes disagree with others they believe are correct, for reasons similar to those explaining agreement with incorrect answers in an Asch (1956) situation. In 3 experiments, we found evidence that people in a position of ignorance sometimes do not agree with the correct answers of others in positions of knowledge. Experiments 1a and 1b found this speaking-from-ignorance (SFI) effect occurred 27% of the time. Experiment 2 introduced experimental controls and self-report data indicating that the SFI effect (30%) was generated by realizing values (e.g., truth, social solidarity) and pragmatic constraints to act cooperatively, rather than by a wide array of alternatives (e.g., normative pressure, reactance). Experiment 3 experimentally manipulated concern for truthfulness, yielding 49% nonagreeing answers, even though there were monetary incentives to give correct, agreeing answers. The overall pattern suggests that people are not so much conformists or independents as they are cooperative truth tellers under social and moral constraints. Results, while surprising for social influence theories, illustrate the dynamics of divergence and convergence that appear across studies in cultural anthropology and developmental psychology, as well as in social psychology.

Inattentiveness in attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with a long-term impact on functioning, productivity and quality of life of patients. This impact is largely due to the symptoms of inattentiveness. However, despite its impairing role in the lives of ADHD patients, inattentiveness has been studied relatively less frequently than have symptoms of impulsivity/hyperactivity and problems with executive function. This review therefore seeks to integrate the neuropsychological theories and current findings in the research fields of neuropsychology, neurophysiology, and neuroimaging, in an attempt to gain a more complete understanding of the role that inattentiveness plays in ADHD, as well as to suggest directions for future studies. The need for a more comprehensive understanding of inattentiveness and ADHD, which integrates findings from each of the three disciplines mentioned above, is emphasized.

Atypical pulvinar-cortical pathways during sustained attention performance in children with attention-deficit/hyperactivity disorder.

OBJECTIVE: The neurobiological basis of inattentiveness, a core feature of attention-deficit/hyperactivity disorder (ADHD), is not yet well understood. Structural abnormalities in thalamus, especially the pulvinar nuclei, have recently been reported in ADHD. Pulvinar nuclei maintain reciprocal connections with cortical/subcortical areas, and play a central coordinating role during visual attention processing. The objective of this study was to test the hypothesis that children and young adolescents with ADHD would show atypical pulvinar-cortical functional pathways during sustained attention performance, and that these functional abnormalities would be associated with the inattentive symptoms of the disorder. METHOD: Visual attention task-based functional magnetic resonance imaging (fMRI) data from 22 children and young adolescents with ADHD and 22 demographically matched, normal control subjects were analyzed. Cortical activation maps and temporal correlations of activity patterns between pulvinar nuclei and the remainder of brain were constructed for each participant. Correlations between activation magnitude of pulvinar and diagnostic measures were calculated in subjects with ADHD. RESULTS: Compared to controls, subjects with ADHD showed significantly reduced pulvinar activations bilaterally, significantly decreased functional connectivity between bilateral pulvinar and right prefrontal regions, and significantly increased connectivity between the right pulvinar and bilateral occipital regions. In addition, the activation magnitude in the left pulvinar was negatively correlated with the DSM-IV inattentive index in ADHD group. CONCLUSIONS: Allied with previous evidence of structural abnormalities in pulvinar, the current data suggest that inappropriate development of pulvinar may lead to disrupted functional circuits for visual attention processing, and that these disruptions contribute significantly to the pathophysiological mechanisms of the inattentiveness symptoms in ADHD.