How default is the default mode of brain function? Further evidence from intrinsic BOLD signal fluctuations

Neuropsychologia. 2006;44(14):2836-45. doi: 10.1016/j.neuropsychologia.2006.06.017. Epub 2006 Aug 1.


The default mode of brain function hypothesis and the presence of spontaneous intrinsic low-frequency signal fluctuations during rest have recently attracted attention in the neuroscience community. In this study we asked two questions: First, is it possible to attenuate intrinsic activity in the self-referential, default mode of brain function by directing the brains resources to a goal-oriented and attention-demanding task? Second, what effect does a sustained attention-demanding overt task performance have on the two intrinsically active networks in the brain, those being the task-negative, default-mode and the anticorrelated, task-positive network? We used functional magnetic resonance imaging to monitor spontaneous intrinsic activity during rest and sustained performance of a sequential two-back working memory task. We compared intrinsic activity during rest and the two-back task to the signal increases and decreases observed in an epoch-related version of the working memory task. Our results show that spontaneous intrinsic activity in the default-mode network is not extinguished but rather attenuated during performance of the working memory task. Moreover, we show that the intrinsic activity in the task-positive network is reorganized in response to the working memory task. The results presented here complements earlier work that have shown that task-induced signal deactivations in the default-mode regions is modulated by cognitive load to also show that intrinsic, spontaneous signal fluctuations in the default-mode regions persist and reorganize in response to changes in external work load.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Brain / blood supply*
  • Brain / physiology*
  • Brain Mapping*
  • Female
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Magnetic Resonance Imaging / methods
  • Male
  • Models, Neurological*
  • Oxygen / blood
  • Principal Component Analysis
  • Spectrum Analysis
  • Statistics as Topic


  • Oxygen