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that can be used to assess intelligence for individuals over age two. First developed in 1910, the test is a standard tool for many school psychologists and yields a mental age (M.A.) and an IQ.

in its revised form, the test provides multiple area IQ scores (called S.A.S.'s) in addition to an overall iQ score. in addition to measuring the verbal and nonverbal areas of a child's development, the Stanford-Binet also provides a quantitative score, measuring the child's mathematical reasoning, and a memory score, measuring the child's short-term memory. (While the Wechsler scales also have subtests which measure these areas, they do not provide iQ scores isolating these abilities.)

The Stanford-Binet test is a good choice for children who are slow at processing information because it contains only one timed subtest. However, this lack of timing can make the testing session extremely long. in addition, test scores may be substantially lower than those resulting from the WAIS-R for very bright individuals over age 16.

See also wechsler intelligence scale for children REVISED (WISC-R).

stars, seeing What appears as random bursts of light when people hit their heads is actually caused by a jolt to the brain cells responsible for vision. Normally, these cells respond to the electrical messages sent by the eyes, interpreting the signals as faces, objects, or whatever people are looking at. But a sudden blow to the head can also trigger activity in visual cells unrelated to, or less active during, the given visual scenario. This overactivity of visual processing cells is a burst of electricity that the brain interprets as bursts of light.

stars most often appear following a blow to the back of the head because that is the location of the visual cortex. In fact, stimulating the cells in this part of the brain with a probe can also set off a twinkling-star show. Scientists also believe that the pulsing star-like visual hallucinations often seen by migraine sufferers is caused by spontaneous electrical signaling in the visual cortex.

While stars do not normally appear unless the head has received a strong blow, the twinkling stars do not usually signal serious problems. on the other hand, the appearance of twinkling lights after only a slight blow—or none at all—should prompt a visit to the physician. Showers of lights or snake-shaped streams of light may signal a torn retina (nerve cells blanketing the back of the eye). A torn retina may be repaired with a laser, but if left untreated the retina may completely detach, causing partial or total blindness.

status epilepticus Repeated or prolonged attacks of epileptic seizures lasting at least five minutes without regaining consciousness between seizures. This medical emergency may be fatal if not treated quickly. This condition is most likely to occur if anticonvulsant drugs are suddenly stopped or taken inconsistently.

stereogram Two pictures each viewed by one eye, which when combined by the brain give the illusion of a three-dimensional shape.

stereotactic radiosurgery Also known as gamma knife surgery, this is a new technique of tightly focused radiation now being used for patients with inoperable brain tumors. The procedure was pioneered in the late 1960s by Lars Leksell, M.D., a swedish neurosurgeon at the Karolinska institute in stockholm. since then, thousands of patients around the world have undergone the procedure to destroy tumors or correct life-threatening blood vessel problems, with no reported deaths or complications from the procedure.

in the technique, the surgeon uses a small directed beam of radiation to treat areas that may be inaccessible by conventional surgery or for patients who may not be able to withstand an operation. The one-time application is an outpatient procedure that may serve as a substitute for the 20 to 30 radiation treatments normally required. using the precisely directed beams of radiation, surgeons can focus on and destroy the diseased tissue and spare nearly all of the surrounding healthy tissue.

The key is to locate the diseased tissue and program those coordinates into a linear accelerator— the unit that emits the radiation beam. The

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