Neurons carry information through the nervous system in the form of brief electrical impulses called action potentials. When an impulse reaches the end of an axon, neurotransmitters are released at junctions called synapses. The neurotransmitters are chemicals that bind to receptors on the receiving neurons, triggering the continuation of the impulse. Fifty different neurotransmitters have been discovered since the first was identified in 1920. By studying the chemical effects of neurotransmit-ters in the brain, scientists have developed treatments for mental disorders and are learning more about how drugs affect the brain.
Scientists once believed that brain cells do not regenerate, thereby making brain injuries and brain diseases untreatable. Since the late 1990s, however, researchers have been testing treatment for such patients with neuron transplants, which introduce nerve tissue into the brain, with promising results. They have also been investigating substances such as nerve growth factor (NGF), which may someday help regenerate nerve tissue.
Technology provides useful tools for researching the brain and helping patients with brain disorders. An electroencephalogram (EEG) records brain waves, which are produced by electrical activity in the brain. It is obtained by positioning electrodes on the head and amplifying the waves with an electroencephalograph. EEGs are valuable in diagnosing brain diseases such as epilepsy and tumors.
Scientists use three other techniques to study and understand the brain and diagnose disorders:
magnetic resonance imaging (mri). Using a magnetic field to display the living brain at various depths, MRI can produce very clear and detailed pictures of brain structures. These images, which often appear as cross-sectional slices, are obtained by altering the main magnetic field of a specific brain area. MRI is particularly valuable in diagnosing damage to soft tissues, such as areas affected by head trauma or stroke. This is crucial when early diagnosis improves the chances of successful treatment. MRI also reveals tumors and other types of brain lesions.
positron emission tomography (pet). During this test, a technician injects the patient with a small amount of a substance, such as glucose, that is marked with a radioactive tag. By tracking the radioactive substance as it travels to the brain, physicians can see almost immediately where glucose is consumed in the brain. This indicates brain activity, an important factor in diagnosing epilepsy, Alzheimer's, or Parkinson's. PET is also valuable in locating tumors and brain areas that have been affected by a stroke or blood clot.
magnetoencephalography (meg). Magneto-encephalography measures the electromagnetic fields created between neurons as electrochemical information is passed along. Of all brain-scanning methods, MEG provides the most accurate indicator of nerve cell activity, which can be measured in milliseconds. By combining an MRI with MEG, clinicians can get a noninvasive look at the brain that is especially useful in diagnosing epilepsy or migraines, for example. MEG also helps identify specific brain areas involved with different tasks. Any movement by the patient—wiggling the toes, for example—appears on the computer screen immediately as concentric colored rings. This pinpoints brain signals even before the toes are actually wiggled. Researchers foresee that these techniques could someday help paralysis victims move by supplying information on how to stimulate their muscles or indicating the signals needed to control an artificial limb.
See also Addiction; Nutrition and mental health
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Laith Farid Gulli, M.D.
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