title: On the temporal characteristics of performance variability in attention deficit hyperactivity disorder (ADHD).
abstract: Increased intra-subject variability of reaction times (ISV-RT) is one of the most consistent findings in attention-deficit/hyperactivity disorder (ADHD). Although the nature of this phenomenon is still unclear, it has been hypothesised to reflect interference from the Default Mode Network (DMN). So far, ISV-RT has been operationally defined either as a frequency spectrum of the underlying RT time series, or as a measure of dispersion of the RT scores distribution. Here, we use a novel RT analysis framework to link these hitherto unconnected facets of ISV-RT by determining the sensitivity of different measures of RT dispersion to the frequency content of the underlying RT time series. N=27 patients with ADHD and N=26 healthy controls performed several visual N-back tasks. Different measures of RT dispersion were repeatedly modelled after individual frequency bands of the underlying RT time series had been either extracted or suppressed using frequency-domain filtering. We found that the intra-subject standard deviation of RT preserves the "1/f noise" characteristic typical of human RT data. Furthermore and most importantly, we found that the ex-Gaussian parameter τ is rather exclusively sensitive to frequencies below 0.025 Hz in the underlying RT time series and that the particularly slow RTs, which nourish τ, occur regularly as part of an quasi-periodic, ultra-slow RT fluctuation. Overall, our results are compatible with the idea that ISV-RT is modulated by an endogenous, slowly fluctuating process that may reflect DMN interference.
authors.affiliation: Department Psychiatry and Psychotherapy, University of Freiburg, Freiburg, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Feige
authors.forename: Monica
authors.initials: M
authors.lastname: Biscaldi
authors.forename: Christopher W N
authors.initials: CW
authors.lastname: Saville
authors.forename: Christian
authors.initials: C
authors.lastname: Kluckert
authors.forename: Stephan
authors.initials: S
authors.lastname: Bender
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ebner-Priemer
authors.forename: Klaus
authors.initials: K
authors.lastname: Hennighausen
authors.forename: Reinhold
authors.initials: R
authors.lastname: Rauh
authors.forename: Christian
authors.initials: C
authors.lastname: Fleischhaker
authors.forename: Christoph
authors.initials: C
authors.lastname: Klein
mesh_terms: D001288:Attention; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D016022:Case-Control Studies; D002648:Child; D004569:Electroencephalography; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time