Mental health is a real struggle for many people, and many don’t even realize they’re genetically disposed to develop a condition like schizophrenia until they’re already dealing with the symptoms.

One of the hallmarks of that particular condition is hearing voices, and scientists now say they know why that happens.

It could very well be the result of “noisy” signaling produced by the brain’s motor system.

If proven, this could drastically alter treatment protocols for auditory hallucinations.

Previously, experts have targeted the auditory system, but this could mean the motor system is where the problem truly lies.

Some schizophrenia patients struggle to differentiate between their own thoughts and external voices, so they believe their own internal monologue is being spoken by a third party. Previous research has indicated this could be due to a brain signal called the corollary discharge, which suppresses the sound of a person’s voice when they are talking.

This is often not working correctly in schizophrenia patients.

The authors of this study believe that a broken corollary discharge is unlikely to tell the whole story, though, because it doesn’t explain positive hallucinatory symptoms.

They believe the efference copy plays a role.

Dr. Xing Tian explained the function of the efference copy.

“When you want to speak, your motor system will generate a very precise signal that indicates what it wants to say. Typically, this signal is accurately targeting at the neurons within the auditory system that reflect the exact sounds a person intends to make.”

Tian and his team believe that a “noisy” efference copy could be what leads to auditory hallucinations.

“‘Noisy’ means that in those patients, those signals are not targeted on the auditory output. They are not precise.”

The study authors tested their hypothesis using electroencephalography (EEG), monitoring the brain activity of 40 schizophrenia patients.

Half “hear voices” but the other half don’t, and the results indicated the auditory responses were not inhibited in either group. That means all of the patients started with a “broken” corollary discharge.”
For patients without auditory hallucination, the efference copy was mapped correctly onto the neural representations for each spoken syllable.

For those who did experience auditory hallucinations, their efference copy was noisy, activating neural responses to sounds other than those being spoken.

This seems to confirm their hypothesis that both pieces of the puzzle must be in play for auditory hallucinations to result.

“Even though they’re called auditory hallucinations, the cause is not all in the auditory system. Maybe the cause is in the network connections from motor to auditory. If we are right, then the treatment should not always target the auditory system.”

They think this will cause a “paradigm shift” in how doctors treat and understand mental illness, because it shifts the focus away from neuro-structural mechanisms.

Good news for anyone looking for help for themselves or a loved one.

The more we understand about how mental illness works, the better.

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