Detection and scaling of task-induced fMRI-BOLD response using resting state fluctuations.
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% CO(2). 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% CO(2)+air). In all subjects who breathed 5% CO(2), RSFA correlated highly with the BOLD response amplitude during 5% CO(2) 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% CO(2), 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% CO(2). 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.
Kannurpatti
Sridhar S
SS
Department of Radiology, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA.
Biswal
Bharat B
BB
D000328:Adult; D000368:Aged; D000465:Algorithms; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide; D003627:Data Interpretation, Statistical; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011597:Psychomotor Performance / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D012146:Rest / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen