Comparison of the experimental BOLD signal change in event-related fMRI with the balloon model

Event-related functional MRI (ER-fMRI) based on both blood oxygenation level-dependent (BOLD) contrast and cerebral blood flow (CBF) contrast has been developed to study the human brain response to transient stimulation. A balloon model has been developed and used in understanding the relationship between changes in CBF and in the BOLD signal in block-designed fMRI. In this report, the balloon model was used to interpret experimental event-related fMRI. Using experimental data acquired from CBF-based ER-fMRI as an input function in the balloon model, stimulated BOLD signal changes were obtained. The simulated time course of the BOLD signal changes was directly compared with the experimentally acquired data. A chi-square (X²) test showed excellent correlation between the simulated and experimental data (α ≤0.05). Our results have demonstrated that the balloon model is useful in interpreting the transient features of the experimental data from the ER-fMRI studies.