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June 10, 1994
Media Contact:Joann Rodgers
Phone: (410) 955-8659
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JRodgers@welchlink.welch.jhu.edu
Johns Hopkins scientists have linked the voices, scrambled language and
distorted thoughts that are the hallmarks of schizophrenia to abnormal physical
changes in specific areas of the human brain that begin by the 32nd week of
pregnancy.
The brain changes occur in a region called the planum temporale (PT) --
located at either temple. "It's an area intimately associated with
comprehending language," says psychiatrist Godfrey Pearlson, M.B. "If you
stimulate the ]PT electrically, a person hears complex sounds similar to a
schizophrenic's auditory hallucinations," he adds.
Pearlson and Patrick Barta, M.D., Ph.D., are co-authors of the study
presented at a May meeting of the American Psychiatric Association in
Philadelphia.
In the study of 14 right-handed schizophrenic patients, the researchers
found that the right PT was much larger than the left when compared with 14
controls, who were individually matched for age, sex, socioeconomic level and
handedness -- all things that may influence brain size. Further, says
Pearlson, the left ]PT of schizophrenic patients was abnormally small.
"Structures related to language, those parts of the brain that make us
uniquely human, tend to be larger on the left side in most of us," says
Pearlson. "Yet more than 90 percent of the schizophrenic patients in the study
have the asymmetry reversed, compared with only 14 percent of the controls,"
says Pearlson.
"This is the first clear demonstration of an abnormality in a specific
'sided' area of the brain that's linked with two key symptoms of the illness,
auditory hallucinations and thought disorder," says Pearlson.
"Sidedness develops relatively early; it's fully obvious by the 32nd week
of pregnancy," he adds. "Although our study doesn't explain why symmetry is
reversed, or precisely what such a reversal means, it supports the idea that in
schizophrenia there's a disruption in normal neurodevelopment that comes very
early in life.
"We've long had clues that disturbances in 'sidedness' of the brain may be
associated with schizophrenia," says Pearlson. "People with epilepsy that
begins in the left temporal lobe of the brain may have symptoms resembling
schizophrenia," he says. People with strokes to the same region often have
disordered language.
An earlier study by co-author Patrick B@ M.D., Ph.D., linked smaller size
of an area encompassing the left PT to severity of patients' auditory
hallucinations.
'ne current study used software that Barta developed to interpret patients'
MRI scans, allowing measurement of the area of each PT. Because the PT "has
hills and bumps," according to Pearlson, such measurements are challenging.
Barta's software permitted the PT to be viewed in three dimensions from a
variety of angles. "It's a virtual reality sort of dissection, which is
obviously preferable to neurosurgery or an eventual autopsy," says Pearlson.
Barta then superimposed triangles of known area over the PT image's surface,
summing their number to get an idea of total area.