Study: Schizophrenia's Hallucinated Voices Drown Out Real Ones

Neurons in the brain communicate via electrical impulses and neurotransmitters. CREDIT: iDesign, Shutterstock View full size image

A new finding in brain science reveals that the voices in a schizophrenia patient's head can drown out voices in the real world — and provides hope that people with the disorder can learn to ignore hallucinatory talk.

The new research pulls together two threads in earlier schizophrenia studies. Many scientists have noticed that when patients hallucinate voices, neurons in brain regions associated with processing sounds spontaneously fire despite there being no sound waves to trigger this activity. That's an indication of brain overload.

But when presented with real-world voices, other studies showed, hallucinating patients' brains often failed to respond at all, in contrast with healthy brains. These studies pointed to a stifling of brain signals.

By analyzing all of these studies together, biological psychologist Kenneth Hugdahl of the University of Bergen in Norway found the simultaneous over-stimulation and dampening of brain signals to be two sides of the same coin. The findings help explain why schizophrenia patients retreat into a hallucinatory world. Now, Hugdahl wants to use this knowledge to help patients reverse that tendency. [Top 10 Mysteries of the Mind]

"What if one could train the patient to shift attention away from the inside voices to voices coming from outside?" Hugdahl said.

Hearing voices that aren't there

To understand how this training would work, it helps to follow Hugdahl's logic back to the beginning. Schizophrenia is incredibly complex, he told LiveScience. The disorder is marked by delusions, hallucinations, breakdowns in thought processes — as many as 35 separate symptoms, presenting differently in every patient.

Hugdahl and his colleagues decided to work toward understanding just one of these symptoms: hallucinations, the most universal mark of schizophrenia (about 70 percent to 80 percent of schizophrenia patients hallucinate). In research published in 2009, the scientists asked hallucinating patients to listen to sounds through headphones while in a functional magnetic resonance imaging (fMRI) scanner. These scanners measure oxygenated blood flow to different brain regions. More blood flow suggests more activity in a given region.

The headphones played two syllables simultaneously, one in the left ear and one in the right ear. For example, the right ear might hear "pa," while the left heard "ta." Patients weren't told the tones were different, but were asked to report what they heard.

Healthy patients generally report hearing the syllable played in the right ear, because the brain is wired for fast transmission of signals from the right ear to the left temporal lobe where speech sounds are processed.

In the absence of outside sound, schizophrenia patients' left temporal speech regions showed hyperactivity, a testament to the real-seeming voices they were hearing in their heads. Hugdahl expected that the addition of real-world sound would only increase the activity in the left temporal lobe, given that more stimulus usually means more activation. But that's not what happened.

"We found, to my big surprise, that they didn't report hearing the right ear sounds when they were hallucinating," he said. "We didn't see activation in the left temporal lobe either."

A brain paradox

This was a paradox. How could the brain be overreacting to nothing and yet shutting down when real sounds came along? To find out if this paradox was real, Hugdahl and University of Bergen researchers Kristiina Kompus and Rene Westerhausen (who is  also affiliated with Bergen's Haukeland University Hospital) dug through earlier studies on schizophrenia to see if other researchers had found the same thing. They found 11 studies that had compared the brains of schizophrenia patients with those of healthy people while listening to external sounds, and 12 studies that looked at the brains of hallucinating schizophrenia participants. No one had ever put two and two together, though — examining the brains of hallucinating patients while they listened to external sounds, for example.

The brain-scan results supported Hugdahl and his colleagues' earlier findings: The paradox appears to be real.

"It obviously must mean that when the hallucinations are taking place in the brain, they interfere with the perceptual system, the system which is there to perceive external stimuli," Hugdahl said.

Training the brain

Hugdahl and his colleagues reported their findings in the October 2011 issue of the journal Neuropsychologia. Now they're taking the research further. It's possible, Hugdahl said, that the simultaneous hyperactivation and quieting of the brain signals is the work of two neurotransmitters, the chemicals that send signals in the brain. One, GABA, is the major inhibitor of the brain: It calms things down, dampening activation. An excess of GABA could be to blame for the lack of response to real-world voices. [10 Stigmatized Health Disorders]

A second neurotransmitter, glutamate, could be the cause of the hallucinations in the first place. Glutamate is an excitatory chemical that gets the brain buzzing. Extra glutamate in the right spot could overactivate the left temporal lobe, triggering false but all-too-real-sounding voices in the mind.

Funded by a prestigious 20 million Norweigen Kroner ($3.5 million) European Research Council Advanced Grant, the researchers are now conducting brain scans with a tool called magnetic resonance spectroscopy, which will allow them to measure levels of GABA and glutamate in various brain regions in schizophrenia patients.

If the finding holds, it could open doors to new drug treatments for schizophrenia symptoms, Hugdahl said. In the meantime, he and his colleagues are trying something outside of the realm of pharmacology. They want to train patients to ignore internal voices and listen to words from the real world.

To do this, the research team has developed an iPhone app that works just like the original dual-hearing experiments. Schizophrenia patients wear headphones that play them a different speech sound in each ear, just as in the original experiments. For 10 or 15 minutes, twice a day, they practice ignoring the sounds to the normally dominant right ear and report the sounds they hear in the weaker left ear.

Only two patients have started this training so far, with one more set to begin next week. At least 20 or 30 will need to complete the training before Hugdahl and his colleagues can tell if the exercises help patients control their attention to competing voices. If it works, it will be a "major breakthrough," Hugdahl said. Early signs are providing some hope.

"The first patient we tested said something very interesting, she said that after she had been using this training for a couple of weeks, she had the feeling that the voices were not controlling her as much as before," Hugdahl said. "She had the feeling that now she could withstand the voices. She was more in control, it was not the voices that were in control. And that's a major achievement."

Correction: This article was updated at 5:30 pm ET to reflect the correct grant amount for Hugdahl's work. It is 20 million Norwegian Kroner, not 20 million Euros. 

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