Brain Imaging

What is Brain Imaging?

Brain imaging is a collection of methods for examining brain structure and function. Different techniques answer different questions: what does the tissue look like, where do physiological signals change during a task, or how does a tracer move through the brain? Routine human scans do not resolve individual neurons.

The methods differ in spatial resolution, timing, and the type of information they provide. Many are non-invasive, although positron emission tomography (PET) typically requires an injection of a radioactive tracer. Electroencephalography (EEG) (EEG) is often discussed alongside brain imaging, but it records electrical activity rather than producing a conventional anatomical scan.

Common Brain Imaging Techniques

Magnetic Resonance Imaging (MRI)

MRI uses a strong magnetic field and radio waves to create detailed images of brain structure. Researchers and clinicians use it to examine anatomy and detect changes such as tumors, lesions, or brain atrophy.

Functional Magnetic Resonance Imaging (fMRI)

Most fMRI studies measure changes in blood oxygenation as an indirect correlate of neural activity. Researchers use these signals to study perception, attention, memory, and decision-making. A highlighted area on a scan does not, by itself, identify a unique mental process. Marcus Raichle's review of functional brain imaging explains the physiological basis of these measurements.

Positron Emission Tomography (PET)

PET uses small amounts of radioactive tracers to measure processes such as glucose metabolism or receptor binding. The information depends on the tracer: different tracers let researchers examine different aspects of disease or drug action. The NIBIB guide to nuclear medicine explains how these images are produced.

Electroencephalography (EEG)

EEG records electrical activity through electrodes on the scalp. Its strength is timing: it helps researchers study when neural responses occur and how activity changes over time. Uses include sleep research, epilepsy assessment, and studies of attention and memory.