Event-related functional MRI: Past, present, and future

Event-related functional MRI: Past, present, and future

^*Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Charlestown, MA 02129; ^†Department of Radiology, Harvard University Medical School, Boston, MA 02115; and ^§Departments of Psychology, Radiology, and Anatomy and Neurobiology, Washington University, St. Louis, MO 63105

Abstract

The past two decades have seen an enormous growth in the field of human brain mapping. Investigators have extensively exploited techniques such as positron emission tomography and MRI to map patterns of brain activity based on changes in cerebral hemodynamics. However, until recently, most studies have investigated equilibrium changes in blood flow measured over time periods upward of 1 min. The advent of high-speed MRI methods, capable of imaging the entire brain with a temporal resolution of a few seconds, allows for brain mapping based on more transient aspects of the hemodynamic response. Today it is now possible to map changes in cerebrovascular parameters essentially in real time, conferring the ability to observe changes in brain state that occur over time periods of seconds. Furthermore, because robust hemodynamic alterations are detectable after neuronal stimuli lasting only a few tens of milliseconds, a new class of task paradigms designed to measure regional responses to single sensory or cognitive events can now be studied. Such “event related” functional MRI should provide for fundamentally new ways to interrogate brain function, and allow for the direct comparison and ultimately integration of data acquired by using more traditional behavioral and electrophysiological methods.

Footnotes

↵ ‡ To whom reprint requests should be addressed at: Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Building 149, 13th Street, Charlestown, MA 02129.
This paper was presented at a colloquium entitled “Neuroimaging of Human Brain Function,” organized by Michael Posner and Marcus E. Raichle, held May 29–31, 1997, sponsored by the National Academy of Sciences at the Arnold and Mabel Beckman Center in Irvine, CA.
↵ ¶ Fisel, C. R., Moore, J. R., Garrido, L., Ackerman, J. L., Rosen, B. R. & Brady, T. J. (1989) Eighth Annual Meeting of the Society of Magnetic Resonance in Medicine
ABBREVIATIONS:

fMRI,

functional MRI;

CBF,

cerebral blood flow;

BOLD,

blood-oxygen-level-dependent;

MEG,

magnetoencephalography