A qualitative test of the balloon model for BOLD-based MR signal changes at 3T.
The aim of this study was to adapt the balloon model for BOLD-based MR signal changes to a magnetic field strength of 3T and to examine its validity. The simultaneous measurement of BOLD and diffusion-weighted BOLD responses was performed. The amplitude of the BOLD peak was found to be similar for all subjects when a short visual stimulus of 6 sec was used. The rise-time to the BOLD peak and the shape and depth of the poststimulus undershoot varied significantly. A fit of the experimental BOLD responses was found to be possible by use of parameters within a reasonable physiological range. The relations between these parameters and their influence on the modeled BOLD responses is discussed. A prediction of the balloon model is the occurrence of a BOLD overshoot, i.e., a lag between the changes of the blood volume and the blood flow after the start of the stimulation. Experimental evidence for the existence of a BOLD overshoot is presented.
Mildner
T
T
Max Planck Institute of Cognitive Neuroscience, Leipzig, Germany. mildner@cns.mpg.de
Norris
D G
DG
Schwarzbauer
C
C
Wiggins
C J
CJ
D001921:Brain / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010775:Photic Stimulation