What is FMRI and how does it work?
Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It has been known for over 100 years (Roy and Sherrington, 1890) that changes in blood flow and blood oxygenation in the brain (collectively known as hemodynamics) are closely linked to neural activity. When nerve cells are active they consume oxygen carried by hemoglobin in red blood cells from local capillaries. The local response to this oxygen utilisation is an increase in blood flow to regions of increased neural activity, occurring after a delay of approximately 1-5 seconds. This hemodynamic response rises to a peak over 4-5 seconds, before falling back to baseline (and typically undershooting slightly). This leads to local changes in the relative concentration of oxyhemoglobin and deoxyhemoglobin and changes in local cerebral blood volume in addition to this change in local cerebral blood flow. Hemo
