Abstract #0535

Liu T, Behzadi Y, Restom K, Townsend J, Smith G

The amplitude and shape of the BOLD signal used in most fMRI studies can be altered by shifts in the baseline vascular state due to factors such as medication, age, and disease. We show that a normalized measure of the power in low frequency (0.1 Hz) components of the BOLD response to a randomized stimulus can be used to probe the baseline vascular state. In preliminary experiments, the normalized measure accounted for 40 to 80% of the variability in BOLD parameters due to both differences in age and the administration of vasoactive agents.