Ten percent is a lot and losses of volume in the frontal lobes are associated with measurable impairment in schizophrenia, psychiatrists have found. But brain volume varies by at least 10 percent from person to person, so volume scans of patients by themselves cannot tell who is sick, the experts say.
Studies using brain scans to measure levels of brain activity often suffer from the same problem: What looks like a "hot spot" of activity change in one person's brain may be a normal change in someone else's.
"The differences observed are not in and of themselves outside the range of variation seen in the normal population," said Dr. Jeffrey Lieberman, chairman of the psychiatry department at Columbia University Medical Center and director of the New York State Psychiatric Institute.
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