The functional magnetic resonance imaging (fMRI) technique measures functional processes in the working brain based on the blood oxygenation level dependent (BOLD) signal. Although it has been confirmed by different techniques that the signal is compatible with neural activity, the BOLD signal does not directly reflect neural activity but rather indicates the level of oxygenation in the blood. With this technique, neural activity is calculated based on slower changes in the vascular system. Therefore, it reflects brain metabolism. In other words, neural activity is indirectly measured in fMRI.
