What does Functional Magnetic Resonance Imaging (fMRI) measure in the brain?

Functional Magnetic Resonance Imaging (fMRI) specifically measures changes in blood flow associated with brain activity, making it a powerful tool for understanding brain function. When neurons in a particular brain area become active, they require more oxygen and nutrients, leading to an increase in blood flow to that region. This change in blood flow is what fMRI detects, allowing researchers to infer which areas of the brain are involved in specific cognitive functions or tasks.

This measurement relies on the principle of hemodynamic response, where the increase in blood flow occurs as a response to the elevated neuronal activity. Thus, fMRI does not directly record electrical activity or chemical imbalances but instead opens a window into the areas of the brain that are engaged during various cognitive activities by using this indirect measure of neural activity. This capability makes fMRI particularly useful for mapping brain function in both research and clinical settings.