Brain Imaging

1924

Hans Berger (1873–1941)

One of the greatest advances in neuroscience and psychology has been the development since the 1950s of increasingly refined brain imaging technologies. Through the intelligent use of these techniques, scientists now know more about the links between brain and behavior than ever before.

Hans Berger invented the electroencephalogram (EEG) in 1924, and it became widely used to measure activity in the human brain. It remains a useful tool for telling scientists when, but not where, activity takes place. Then, in 1963, the computed tomography (CT) scan was patented. Computerized axial tomography (CAT) uses a series of X-ray “slices,” or pictures, to reconstruct a detailed image of a part of the brain. It has been very useful as a diagnostic tool in locating tumors and abnormalities.

In 1972, after almost two decades of research, medical practitioner Raymond Damadian patented the first magnetic resonance imaging (MRI) machine, which he envisioned as a tool for detecting cancerous cells. The technology has continued to be refined, and today an MRI detects changes in the alignment of the nuclei of brain cells when a radio wave is passed through the brain. The results are analyzed by a computer, which then constructs a 3-D image that shows healthy and diseased tissue, as well as blood clots and other pathologies.

Brain activity can be detected by a positron emission tomography (PET) scan, which tracks injected radioactive glucose as it is used in the brain. The brain cells that are most active will show the greatest use of the glucose.

The most powerful technique now in use is the functional MRI (fMRI), which tracks the use of oxygen in the blood. When neurons are active, they use more oxygen, thus activity in any one part of the brain can be tracked as it happens. Neuroscientists now rely extensively on fMRI images to study almost every facet of human brain functioning.

SEE ALSO Neurotransmission (1921), Split-Brain Studies (1962)

PET/MRI hybrid images of the brain identify diseased brain tissue, in addition to tracking neuronal activity.