Functional magnetic resonance imaging in the visual system

Functional magnetic resonance imaging (fMRI) is a relatively new technique for measuring brain function during resting and activated conditions with g ood spatial and temporal resolution. Because of it robust and reproducible activation response to visual stimuli in the occipital cortex, many studies have been directed at visual function. Toe methodology has been refined pr ogressively to allow more accurate detection of the small activation signal , and using computational mapping foci of cerebral activity have been displ ayed in a two-dimensional format. Several factors modifying the activation signal have been identified. fMRI has been used to define the retinotopic representation of areal bounda ries and the localization of higher visual functions in the occipital corte x. Motion perception in area middle temporal (MT) is well-recognized, but e ye movement studies are limited. The activated signal may have significant implications for our understandin g of brain metabolism but cerebral blood flow and oxygenation sensitive rec ordings after prolonged visual stimulation have given conflicting results. Clinically, fMRI can follow changes in cerebral activity during a progressi ve neurologic illness and measure responses to treatment. Neurosurgical pla nning in disorders such as epilepsy may be facilitated.