Functional MRI is a safe, non-invasive process by which activity in the brain may be studied on people in vivo. In preparation for a scan, a participant placed inside the magnetic resonance imaging scanner. A strong magnetic field, generally ranging from 1.5T (tesla) to 7T, polarizes targeted molecules in the brain and surrounding tissues. For fMRI these are typically hydrogen protons. These molecules respond to strong magnetic fields and so line up with the magnetic field produced by the scanner.

By disturbing the alignment of these protons to various degrees, a signal can be collected which describes the nature of a particle’s disalignment or realignment with the primary magnetic field. Every substance responds to these fluctuations in a way that is uniquely characteristic to its chemical composition. An fMRI targets the amount of oxygen-rich hemoglobin present in the blood. This is the blood oxygen level dependant signal, or BOLD signal.

Astroglial cells supporting neurons monitor the metabolism of the neurons. When a neuron begins firing, consuming resources more rapidly, astroglial cells expand nearby blood vessels to provide the neurons more oxygen and glucose. More oxygen than is used by the neuron is supplied. The relative increase of oxygenated hemoglobin in these areas is interpreted to mean increased firing of nearby neurons indicating activity in that area while performing a task. These measurements show the brain processes occurring in real time.

With over 15 years of research, the relationship between the BOLD signal and neuronal activity is well understood and predictable. Experiments conducted using fMRI as a tool to gather data have yielded theoretically and pragmatically relevant results. At the Functional Neuroimaging Lab we hope to continue in this endeavor.