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 sign al 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 a ll subjects when a short visual stimulus of 6 sec was used. The rise-time t o the BOLD peak and the shape and depth of the poststimulus undershoot vari ed 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 a nd the blood flow after the start of the stimulation. Experimental evidence for the existence of a BOLD overshoot is presented. (C) 2001 Wiley-Liss, I nc.