Neurons, Hormones, and the Brain

Studying the Brain

To examine the brain’s functions, researchers have to study a working brain, which means they can’t use cadavers. Invasive studies, in which researchers actually put instruments into the brain, can’t be done in humans, though they can be done occasionally during medically necessary brain surgery. Researchers usually use invasive techniques in animal studies. There are two main types of invasive animal studies:

• Lesioning studies: Researchers use an electrode and an electric current to burn a specific, small area of the brain.
• Electric stimulation of the brain: Researchers activate a particular brain structure by using a weak electric current sent along an implanted electrode.

Because they cannot use such invasive techniques on humans, researchers study human brains in two ways:

• They examine people with brain injuries or diseases and see what they can and can’t do.
• They use electroencephalographs (EEGs), which can record the overall electrical activity in the brain via electrodes placed on the scalp.

Recently, high-tech innovations have made studying human brains easier. Researchers use three types of imaging equipment to study the brain:

• Computerized tomography (CT): In CT, a number of x-rays are taken of the brain from different angles. A computer then combines the x-rays to produce a picture of a horizontal slice through the brain.
• Magnetic resonance imaging (MRI): Both brain structure and function can be visualized through MRI scans, which are computer-enhanced pictures produced by magnetic fields and radio waves.
• Positron emission tomography (PET): For PET scans, researchers inject people with a harmless radioactive chemical, which collects in active brain areas. The researchers then look at the pattern of radioactivity in the brain, using a scanner and a computer, and figure out which parts of the brain activate during specific tasks, such as lifting an arm or feeling a particular emotion.