Is the ADHD brain wired differently? A review on structural and functional connectivity in attention deficit hyperactivity disorder

Abstract

In recent years, a change in perspective in etiological models of attention deficit hyperactivity disorder (ADHD) has occurred in concordance with emerging concepts in other neuropsychiatric disorders such as schizophrenia and autism. These models shift the focus of the assumed pathology from regional brain abnormalities to dysfunction in distributed network organization. In the current contribution, we report findings from functional connectivity studies during resting and task states, as well as from studies on structural connectivity using diffusion tensor imaging, in subjects with ADHD. Although major methodological limitations in analyzing connectivity measures derived from noninvasive in vivo neuroimaging still exist, there is convergent evidence for white matter pathology and disrupted anatomical connectivity in ADHD. In addition, dysfunctional connectivity during rest and during cognitive tasks has been demonstrated. However, the causality between disturbed white matter architecture and cortical dysfunction remains to be evaluated. Both genetic and environmental factors might contribute to disruptions in interactions between different brain regions. Stimulant medication not only modulates regionally specific activation strength but also normalizes dysfunctional connectivity, pointing to a predominant network dysfunction in ADHD. By combining a longitudinal approach with a systems perspective in ADHD in the future, it might be possible to identify at which stage during development disruptions in neural networks emerge and to delineate possible new endophenotypes of ADHD. Hum Brain Mapp 31:904-916,

Abnormal MEG Oscillatory Activity during Visual Processing in the Prefrontal Cortices and Frontal Eye-Fields of the Aging HIV Brain

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“…Restingstate [40] and cognitive [41,42] neuroimaging findings have consistently shown hypoactivity in these circuits in ADHD patients. And activity in the cerebellum is correlated with the severity of ADHD symptoms [43] or the effect of MPH treatment [36] , which are in line with our correlation results.…”

The Roots of Autism and ADHD Twin Study in Sweden (RATSS)

“…In addition, we expect these differences to be associated with functional and structural neurobiological characteristics, particularly over-and under-connectivity in ASD, and eventually in ADHD (Konrad & Eickhoff, 2010), as well as with molecular brain characteristics (e.g., GABA (gamma-aminobutyric acid), glutamate dysregulation). We also hypothesize that these mechanisms correlate with cognitive phenotypes (e.g., ASD: social cognition, attention to detail, flexibility, planning; ADHD: working memory, inhibition, timing, reward dependence), with categorically and dimensionally defined ASD/ADHD and ASD/ADHD symptoms, and with functional impairment.…”