We describe almost entirely automated procedures for estimation of global, voxel, and cluster-level statistics to test the null hypothesis of zero neuroanatomical difference between two groups of structural magnetic resonance imaging (MRI) data. Theoretical distributions under the null hypothesis are available for 1) global tissue class volumes; 2) standardized linear model [analysis of variance (ANOVA and ANCOVA)] coefficients estimated at each voxel; and 3) an area of spatially connected clusters generated by applying an arbitrary threshold to a two-dimensional (2-D) map of normal statistics at voxel level. We describe novel methods for economically ascertaining probability distributions under the null hypothesis, with fewer assumptions, by permutation of the observed data. Nominal Type I error control by permutation testing is generally excellent; whereas theoretical distributions may be over conservative. Permutation has the additional advantage that it can be used to test any statistic of interest, such as the sum of suprathreshold voxel statistics in a cluster (or cluster mass), regardless of its theoretical tractability under the null hypothesis. These issues are illustrated by application to MRI data acquired from 18 adolescents with hyperkinetic disorder and 16 control subjects matched for age and gender.

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ADHD is associated with subnormal activation of the prefrontal systems responsible for higher-order motor control. Functional MRI is a feasible technique for investigation of neural correlates of ADHD.

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The Strengths and Difficulties Questionnaire (SDQ) is a brief behavioural screening questionnaire that can be completed in about 5 minutes by the parents and teachers of 4-16 year olds. The scores of the English version correlate well with those of the considerably longer Child Behavior Checklist (CBCL). The present study compares the German versions of the questionnaires. Both SDQ and CBCL were completed by the parents of 273 children drawn from psychiatric clinics (N = 163) and from a community sample (N = 110). The children from the community sample also filled in the SDQ self-report and the Youth Self Report (YSR). The children from the clinic sample received an ICD-10 diagnosis if applicable. Scores from the parent and self-rated SDQ and CBCL/YSR were highly correlated and equally able to distinguish between the community and clinic samples, with the SDQ showing significantly better results regarding the total scores. They were also equally able to distinguish between disorders within the clinic sample, the only significant difference being that the SDQ was better able to differentiate between children with and without hyperactivity-inattention. The study shows that like the English originals, the SDQ-Deu and the German CBCL are equally valid for most clinical and research purposes.

Attention-deficit hyperactivity disorder is characterised by specific deficits in tasks of motor response inhibition, but not motor timing, and by dysfunction of frontostriatal brain regions.

This pattern of spatially distributed grey matter deficit in the right hemisphere is compatible with the hypothesis that ADHD is associated with disruption of a large scale neurocognitive network for attention. The left hemispheric white matter deficits may be due to dysmyelination.

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