The first imaging technologies, the X-ray and EEG (electroencephalogram), were primitive by today's standards, but both have been considerably improved—and they provided the conceptual base of the other amazing imaging technologies that have recently emerged.

Computerized brain imaging technologies now measure and display the variations in chemical composition, blood-flow patterns, and electromagnetic fields that occur in normal and/or abnormal brains. Each of the several current forms of brain imaging technology has strengths and weaknesses, and new developments are continually making the technology faster, more powerful, less invasive, and less expensive. Imaging technology was primarily used in medical diagnosis initially, but it is being increasingly used in pure neuroscience and psychological research.

Educational researchers are just beginning to use imaging technologies, but this use will dramatically increase in the coming years. It will revolutionize educational research and many elements of educational policy and practice.

The various computerized imaging technologies differ, but the following analogy demonstrates how someone can examine internal differences in something (a brain) that has a protective cover (a skull): Imagine that you're looking for similarities, differences, and imperfections in successive slices of a thinly sliced apple or potato. A brain-imaging machine is basically a camera that can rapidly and successively change its focus as it photographs and digitally stores successive thin slices of a brain in order to create a comprehensive three-dimensional image of selected properties of the entire brain.

The graphic displays in imaging technology typically use the color spectrum gradations to represent the activity levels of the various brain areas in a scan (the red end of the spectrum representing a high level of activity in a brain area, the purple end representing low activity, and the other colors representing intermediate levels). Topographical maps similarly use different colors to represent elevations (mountains, valleys, etc). A scan of a slice of brain thus graphically indicates which brain areas were active and inactive during the time interval of the scan.