Scientists Trace 'Voices' in Schizophrenia
By DANIEL GOLEMAN
Published: September 22, 1993
HEARING voices, the hallmark symptom of schizophrenia, occurs when there is a heightened activity in the same part of the brain people use when they speak or think words, new findings suggest.
The results support a leading psychological theory of auditory hallucinations, which proposes that when people with schizophrenia hear voices, they are unable to recognize them as their own thoughts, and so perceive them as words spoken by someone else.
The researchers used a brain scanning technique to study the cerebral blood flow in schizophrenic men while they were having auditory hallucinations and again later when the men were not hallucinating. They found that the greatest neural activity during the auditory hallucinations was in Broca's area, the brain's speech center. The findings are reported in the current issue of Lancet, a medical journal published in Britain, by Dr. P. K. McGuire and colleagues at King's College Hospital in London. Significance of Finding
"It's an exciting finding," said Dr. Richard Jed Wyatt, chief of the neuropsychiatry branch at the National Institute of Mental Health in Bethesda, Md. "It's one of the first times we've been able to localize a specific, focal area of the brain active during a cognitive process in a living person with schizophrenia."
The study used single photon emission computed tomography, an imaging technique that offers a snapshot of blood flow in the brain of a person who has been injected with a brew of short-lived radioactive isotopes. The isotopes, swept along with the blood, quickly flow to the parts of the brain that are most active at that moment, lighting up those areas in X-ray images.
This was the first study to use the method with patients while they were hearing voices, thus offering a picture of the parts of the brain most active during auditory hallucinations.
The test was done on 12 men with schizophrenia who reported hearing voices, and was repeated an average of five months later, after a course of medication had reduced their symptoms, including the auditory hallucinations. In the first test, the men were trained to raise a finger to signal they were hearing voices so that the brain imaging could capture activity while they were hallucinating.
None of the men reported having the auditory hallucinations during the second test, which allowed a comparison with brain activity in the first test.
"Broca's area is a surprise, since that's where you make sounds, not where you hear them," said Dr. Jerome Engel, a neurologist at the medical school of the University of California at Los Angeles. "I would have expected more brain activity in Wernicke's area, which is where you hear; the usual assumption is that people are listening to thoughts during auditory hallucinations. But this finding suggests that, in terms of unusual brain activity, auditory hallucinations have more to do with the generation of words in the brain than listening to them."
The new findings support those of a 1992 American study that used less precise brain imaging techniques with patients who reported auditory hallucinations. That study, reported in The American Journal of Psychiatry, found reduced activity in Wernicke's area and increased activity in Broca's area.
In the new study, there were also slightly elevated levels in the left temporal lobe, the site of the auditory cortex, where the meanings of sounds are recognized. The left temporal lobe is the most common site of epileptic seizures that produce auditory hallucinations, and it is also the area where direct electrical stimulation produces the experience of hearing voices.
Several researchers, using autopsies and other techniques, have found abnormalities in the left temporal lobe in people in whom schizophrenia has been diagnosed. The new study marks a major change in research strategy, with imaging techniques allowing the study of brain activity while a person is having a given experience.
The new study also found a slight elevation in activity in the left anterior cingulate cortex, a region closely connected with the limbic system, which regulates emotions. The words heard by schizophrenics during auditory hallucinations are often loaded with feelings.
Diagram: "Looking for Voices in the Brain" New research on the auditory hallucinations common in schizophrenia has tracked the blood flow in the brain that reflects the neural activity of people as they hear such voices. The greatest activity was found in Broca's area, the brain's speech center. It is also activated when people who do not have schizophrenia silently talk to themselves. An earlier study of auditory hallucinations also found an increase in activity in Broca's area and reduced activity in Wernicke's area, which is associated with hearing. The new study also found a slight increase in the left temporal lobe, site of the auditory cortex, where the meanings of sounds are recognized, and in the left anterior cingulate cortex (not shown), associated with emotions. Diagram shows locations of Broca's area (speech center) and Wernicke's area (hearing center)