Detection and scaling of task-induced fMRI-BOLD response using resting state fluctuations

Sridhar S. Kannurpatti, Bharat B. Biswal

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114 Scopus citations


This study evaluated a calibration technique for scaling the fMRI-BOLD response during a simple motor task. A novel scaling parameter, resting state physiological fluctuation amplitude (RSFA), was tested using previously established scaling factors such as breath hold or 5% CO2. RSFA was hypothesized to contain vascular reactivity information present in the resting state fMRI signal. Subjects were scanned under various stimulus conditions: (a) rest while breathing room air, (b) bilateral fingertapping, (c) breath holding and (d) moderate hypercapnia (breathing 5% CO2 + air). In all subjects who breathed 5% CO2, RSFA correlated highly with the BOLD response amplitude during 5% CO2 inhalation. Also, RSFA correlated highly with the amplitude of the BOLD response elicited by breath hold. RSFA was therefore used as a hemodynamic scaling factor to calibrate both the amplitude and spatial extent of the fMRI-BOLD response during the motor task (fingertapping). Results revealed that amplitude scaling using RSFA was similar to that using breath hold or 5% CO2, where the spatial extent of activation diminished by 20-37% over all subjects. Spatial extent of activation changed significantly after scaling and only 30-40% of the activated area overlapped with the unscaled activation. RSFA-scaled task-induced fMRI-BOLD response in both amplitude and spatial extent was comparable to that obtained using breath hold or 5% CO2. We conclude that RSFA may be used to hemodynamically scale the fMRI-BOLD response and does not require the use of a hypercapnic challenge (which may not be purely non-neural), which can be difficult to implement in special populations.

Original languageEnglish (US)
Pages (from-to)1567-1574
Number of pages8
Issue number4
StatePublished - May 1 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neurology
  • Cognitive Neuroscience


  • BOLD
  • Breath hold
  • CBF
  • CO
  • Hemodynamic
  • Hypercapnia
  • Motor cortex
  • Scaling
  • fMRI


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