Functional Magnetic Resonance Imaging (commonly written fMRI) measures brain blood flow patterns and metabolic changes. Although almost a dozen different kinds of imaging technologies exist, fMRI is perhaps the currently most important of the group for cognitive neuroscience researchers. fMRI permits them to identify specific brain regions that are active when the subject is carrying out a task, such as reading a text, making a decision, or moving a finger. Scientists can thus compare the brain anatomy and activity of people who read well and poorly, or who make appropriate and inappropriate decisions. Much of what we've learned recently about cognition has been carried out with fMRI technology.

Positron Emission Tomography (PET) is another important imaging technology. Scientists using PET insert a small amount of radioactively tagged glucose (or other compound) into the bloodstream of the experimental subject. Since glucose is the brain's principal food, the PET scans of subjects will reveal the brain areas that are the most active (those with the most glucose) when, for example, the subjects are asked to say the first verb that comes to mind when they hear a specific noun—such as cut or slice when they hear the noun knife.

Emerging major advances in EEG (electroencephalogram) technology may provide the best initial and potential venue for educational researchers. EEG is the least invasive, cheapest, and most portable of the imaging technologies. For example, since fMRI uses powerful magnets and PET uses radioactive isotopes, and both require expensive equipment in specialized laboratory settings, their use in educational research has been limited by ethical and financial considerations. Conversely, EEG measures electrical brain waves via electrodes placed on the skull, and so it's no more invasive than a blood pressure sleeve. Further, the electrodes can now be placed inside a cap where they send wireless signals to a nearby computer, so a researcher could eventually observe brain activity in non-laboratory settings, such as within a classroom.

Although we're excited about the potential use of imaging technologies in our understanding of many current cognitive mysteries, and in the diagnosis and treatment of learning disabilities, worrisome issues exist. Imaging technologies can also become potentially superb lie detectors, and so their use and possible misuse in government, business, and our criminal justice system poses serious issues about the nature of privacy. For example, if police can't enter a suspect's house without a warrant, can they technologically enter a suspect's skull in search of evidence without the equivalent of a warrant?

Each recent technological and biological advance has brought both promise and concern. Brain imaging technology thus joins recent advances in genetics, medicine, and computer technology as another element of what promises to be an intellectually stimulating and challenging era.