Functional imaging of the brain.

New neurophysiological methods such as 2-deoxy-D-glucose (2DG) autoradiography have stimulated rapid changes in emission imaging with radionuclides. It has been recognized that general imaging concepts and methods can be applied to many interactions of waves, particles, or fields within the body. X-ray computed tomography, single-photon emission computerized tomography, positron emission tomography, and nuclear magnetic resonance imaging have the potential to enable us to visually observe biochemical events and physiological processes in the brain, where our knowledge is limited and our eagerness to understand function is the greatest.