title: Resting state fMRI entropy probes complexity of brain activity in adults with ADHD.
abstract: In patients with attention deficit hyperactivity disorder (ADHD), quantitative neuroimaging techniques have revealed abnormalities in various brain regions, including the frontal cortex, striatum, cerebellum, and occipital cortex. Nonlinear signal processing techniques such as sample entropy have been used to probe the regularity of brain magnetoencephalography signals in patients with ADHD. In the present study, we extend this technique to analyse the complex output patterns of the 4 dimensional resting state functional magnetic resonance imaging signals in adult patients with ADHD. After adjusting for the effect of age, we found whole brain entropy differences (P=0.002) between groups and negative correlation (r=-0.45) between symptom scores and mean whole brain entropy values, indicating lower complexity in patients. In the regional analysis, patients showed reduced entropy in frontal and occipital regions bilaterally and a significant negative correlation between the symptom scores and the entropy maps at a family-wise error corrected cluster level of P<0.05 (P=0.001, initial threshold). Our findings support the hypothesis of abnormal frontal-striatal-cerebellar circuits in ADHD and the suggestion that sample entropy is a useful tool in revealing abnormalities in the brain dynamics of patients with psychiatric disorders.
authors.affiliation: MRC Centre for Neuropsychiatric Genetics and Genomics, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff School of Medicine, Cardiff University, Cardiff, UK; Imaging Science, Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, UK. Electronic address: SokunbiMO@cardiff.ac.uk.
authors.forename: Moses O
authors.initials: MO
authors.lastname: Sokunbi
authors.forename: Wilson
authors.initials: W
authors.lastname: Fung
authors.forename: Vijay
authors.initials: V
authors.lastname: Sawlani
authors.forename: Sabine
authors.initials: S
authors.lastname: Choppin
authors.forename: David E J
authors.initials: DE
authors.lastname: Linden
authors.forename: Johannes
authors.initials: J
authors.lastname: Thome
mesh_terms: D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000473:pathology / Q000503:physiopathology*; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D001931:Brain Mapping; D002531:Cerebellum / Q000473:pathology / Q000503:physiopathology; D003342:Corpus Striatum / Q000473:pathology / Q000503:physiopathology; D019277:Entropy; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012146:Rest
keywords: ADHD; BOLD; Complexity; Sample entropy; fMRI