A lack of default network suppression is linked to increased distractibility in ADHD

Catherine Fassbender, Hao Zhang, Wendy M. Buzy, Carlos R. Cortes, Danielle Mizuiri, Laurel A Beckett, Julie B Schweitzer

Research output: Contribution to journalArticlepeer-review

221 Scopus citations


Heightened distractibility in participants with ADHD as indexed by increased reaction time (RT) variability has been hypothesized to be due to a failure to sufficiently suppress activation in the default attention network during cognitively demanding situations. The present study utilized fMRI to examine the relationship between intra-individual variability (IIV) in task RT and suppression of BOLD response in regions of the default network, using a working memory paradigm and two levels of control tasks. IIV was calculated separately for thirteen healthy control and twelve children with ADHD, Combined Type. Children with ADHD displayed significantly more RT variability than controls. Neural measures showed that although both groups displayed a pattern of increasing deactivation of the medial prefrontal cortex (PFC) with increasing task difficulty, the ADHD group was significantly less deactive than controls. Correlations between IIV and brain activation suggested that greater variability was associated with a failure to deactivate ventromedial PFC with increasing task difficulty. T-tests on brain activation between participants with ADHD with low versus high IIV implicated a similar region so that high variability was associated with greater activity in this region. These data provide support for the theory that increased distractibility in at least some participants with ADHD may be due to an inability to sufficiently suppress activity in the default attention network in response to increasing task difficulty.

Original languageEnglish (US)
Pages (from-to)114-128
Number of pages15
JournalBrain Research
StatePublished - Jun 1 2009


  • ADHD
  • Default attention network
  • fMRI
  • Medial prefrontal cortex
  • Variability

ASJC Scopus subject areas

  • Neuroscience(all)
  • Clinical Neurology
  • Developmental Biology
  • Molecular Biology


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