title: Complexity analysis of spontaneous brain activity in attention-deficit/hyperactivity disorder: diagnostic implications.
abstract: BACKGROUND
  Attention-deficit/hyperactivity disorder (ADHD) is defined as the most common neurobehavioral disorder of childhood, but an objective diagnostic test is not available yet to date. Neurophychological, neuroimaging, and neurophysiological research offer ample evidence of brain and behavioral dysfunctions in ADHD, but these findings have not been useful as a diagnostic test.
  
  
  METHODS
  Whole-head magnetoencephalographic recordings were obtained from 14 diagnosed ADHD patients and 14 healthy children during resting conditions. Lempel-Ziv complexity (LZC) values were obtained for each channel and child and averaged in five sensor groups: anterior, central, left lateral, right lateral, and posterior.
  
  
  RESULTS
  Lempel-Ziv complexity scores were significantly higher in control subjects, with the maximum value in anterior region. Combining age and anterior complexity values allowed the correct classification of ADHD patients and control subjects with a 93% sensitivity and 79% specificity. Control subjects showed an age-related monotonic increase of LZC scores in all sensor groups, while children with ADHD exhibited a nonsignificant tendency toward decreased LZC scores. The age-related divergence resulted in a 100% specificity in children older than 9 years.
  
  
  CONCLUSIONS
  Results support the role of a frontal hypoactivity in the diagnosis of ADHD. Moreover, the age-related divergence of complexity scores between ADHD patients and control subjects might reflect distinctive developmental trajectories. This interpretation of our results is in agreement with recent investigations reporting a delay of cortical maturation in the prefrontal cortex.
authors.affiliation: Departamento de Psiquiatría, Universidad Complutense de Madrid, Madrid, Spain. aferlucas@med.ucm.es
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernández
authors.forename: Javier
authors.initials: J
authors.lastname: Quintero
authors.forename: Roberto
authors.initials: R
authors.lastname: Hornero
authors.forename: Pilar
authors.initials: P
authors.lastname: Zuluaga
authors.forename: Marta
authors.initials: M
authors.lastname: Navas
authors.forename: Carlos
authors.initials: C
authors.lastname: Gómez
authors.forename: Javier
authors.initials: J
authors.lastname: Escudero
authors.forename: Natalia
authors.initials: N
authors.lastname: García-Campos
authors.forename: Joseph
authors.initials: J
authors.lastname: Biederman
authors.forename: Tomás
authors.initials: T
authors.lastname: Ortiz
mesh_terms: D000375:Aging; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000503:physiopathology*; D001921:Brain / Q000254:growth & development / Q000503:physiopathology*; D016022:Case-Control Studies; D002648:Child; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D012680:Sensitivity and Specificity