Brain functional MRI: Physiological, technical, and methodological bases, and clinical applications

Brain functional MRI (fMRI) provides an indirect mapping of cerebral activi ty, based on the detection of the local blood flow and oxygenation changes following neuronal activity (BOLD contrast, Blood Oxygenation Level Depende nt). fMRI allows us to study non invasively the normal and pathological asp ects of cortical functional organization. Each fMRI study compares two diff erent states of activity. Echo-Planar Imaging (EPI) is the technic of choic e that makes it possible to study the whole brain at a rapid pace. Activati on maps are calculated from a statistical analysis of the local signal chan ges. Functional MRI is now becoming an essential tool in the neurofunctiona l work-up of many neurosurgery patients, as well as the reference method to image normal or pathologic functional brain organization in adults and chi ldren.