title: Capturing the dynamics of response variability in the brain in ADHD.
abstract: ADHD is characterized by increased intra-individual variability in response times during the performance of cognitive tasks. However, little is known about developmental changes in intra-individual variability, and how these changes relate to cognitive performance. Twenty subjects with ADHD aged 7-24 years and 20 age-matched, typically developing controls participated in an fMRI-scan while they performed a go-no-go task. We fit an ex-Gaussian distribution on the response distribution to objectively separate extremely slow responses, related to lapses of attention, from variability on fast responses. We assessed developmental changes in these intra-individual variability measures, and investigated their relation to no-go performance. Results show that the ex-Gaussian measures were better predictors of no-go performance than traditional measures of reaction time. Furthermore, we found between-group differences in the change in ex-Gaussian parameters with age, and their relation to task performance: subjects with ADHD showed age-related decreases in their variability on fast responses (sigma), but not in lapses of attention (tau), whereas control subjects showed a decrease in both measures of variability. For control subjects, but not subjects with ADHD, this age-related reduction in variability was predictive of task performance. This group difference was reflected in neural activation: for typically developing subjects, the age-related decrease in intra-individual variability on fast responses (sigma) predicted activity in the dorsal anterior cingulate gyrus (dACG), whereas for subjects with ADHD, activity in this region was related to improved no-go performance with age, but not to intra-individual variability. These data show that using more sophisticated measures of intra-individual variability allows the capturing of the dynamics of task performance and associated neural changes not permitted by more traditional measures.
authors.affiliation: NICHE Lab, Department of Psychiatry, Rudolf Magnus Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Janna
authors.initials: J
authors.lastname: van Belle
authors.affiliation: NICHE Lab, Department of Psychiatry, Rudolf Magnus Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Tamar
authors.initials: T
authors.lastname: van Raalten
authors.affiliation: NICHE Lab, Department of Psychiatry, Rudolf Magnus Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Dienke J
authors.initials: DJ
authors.lastname: Bos
authors.affiliation: Department of Psychological Sciences, Vanderbilt University, Nashville, USA.
authors.forename: Bram B
authors.initials: BB
authors.lastname: Zandbelt
authors.affiliation: NICHE Lab, Department of Psychiatry, Rudolf Magnus Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Bob
authors.initials: B
authors.lastname: Oranje
authors.affiliation: NICHE Lab, Department of Psychiatry, Rudolf Magnus Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Sarah
authors.initials: S
authors.lastname: Durston
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D002648:Child; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D055815:Young Adult
keywords: ADHD; Development; Ex-Gaussian; Functional MRI; ICA; Response variability