One way to ascertain the function of a certain part of the brain is to give brain-damaged subjects a task that requires a particular skill. If the subjects can perform the task well, we know that the damaged area is not responsible for that skill. On the other hand, if they fail the task while non-damaged subjects succeed, we know that the damaged area must play some role in mediating the missing skill. Once their validity has been established, we can use these neuropsychological tests to find out how well a certain part of the brain is functioning.

In research, brain damage usually stems from one of two causes: organic brain damage or ablation. Organic damage occurs when part of the brain is knocked out by some natural event, such as a stroke or an accident. This is the most ethically sound method of research, since the researchers do not cause any damage to the subjects. However, organic damage is usually not clean-cut, and it is often not clear which parts of the brain have been truly knocked out. A patient might appear to have damage to the frontal lobe, but the damage might leak over into the temporal lobe as well, or enough of the frontal area might be left intact to preserve its function.

Because of these constraints, some researchers prefer to create the damage themselves by ablating a certain area of the brain. Ablation can be performed by administering anything that will kill cells within a certain radius. One preferred method is chemical ablation, in which a toxic chemical is leaked through a thin tube into the area to be damaged. Ablations are much more clean-cut than organic damage, but, due to obvious ethical concerns, they cannot be performed on humans. Instead, researchers often ablate the brains of animals. Unfortunately, animals' brains are somewhat different from our own, so it is difficult to say whether results from experiments with animals would also hold true for humans.

Another way that researchers can study the functions of specific areas of the brain is by taking pictures of it. These techniques are minimally invasive, yet can still provide anatomically detailed information. Previously, researchers could only take still images of the brain using MRI or CT scan technology. However, new dynamic techniques, like functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), can take many pictures per minute, providing researchers with a picture of the brain in motion. These techniques show the changes in blood flow during neuropsychological tests. Another dynamic method of research, electroencephalography (EEG), measures changes in electrical current in the brain. Each technique is discussed in more detail below.

Functional magnetic resonance imaging (fMRI) is a powerful new technique that allows scientists to watch the brain at work by measuring oxygenated blood flow using a giant magnet. Using fMRI technology, scientists can watch the brain at work and see which areas "light up" when people perform particular tasks. A person lies flat in a tube surrounded by a giant magnet, which takes many pictures of their brain each second. As he or she performs a particular task, for example, a language-based task such as naming pictures, blood flows to the active portions of the brain to provide them with energy to work. Thus, scientists can tell which areas are active by watching the patterns of blood flow. In the above example, the language-processing area of the brain would need increase blood flow to perform the task, and this increase would show up on the fMRI scan as more brightly colored area. Scientists could then conclude that this brightly-colored area must be the area involved in processing language (specifically, in generating names to match pictures). Unfortunately, using fMRI for research is currently very expensive, due to the high cost for equipment to take measurements and analyze data.

Positron emission tomography (PET) is another way that researchers can image the brain at work. Subjects are injected with a radioactive dye, which is incorporated into their bloodstream and into the brain's capillaries. The easily detectable radioactivity therefore correlates with blood flow, so researchers can analyze the brain's use of glucose and oxygen by watching where the radioactivity goes in the brain. In this way, the principle of PET is similar to fMRI. However, fMRI is often favored as a research technique because it does not require injections of radioactivity into human subjects, and because it is cheaper to use per subject.

Electroencephalograph (EEG) technology is an older method for studying the brain, but it is still used to study electrical activity, rather than blood flow. EEG measures patterns of localized electrical activity through electrodes placed on the scalp. Because action potentials are electrical events, very active areas will show large amounts of electrical activity, which can be detected by EEG. EEG can also detect wave-like patterns of neural activity that can give clues to a person's circadian rhythms.