What Happens to the Brain During Hallucinations? Scientists Gave Mice Drugs to Find Out

Hallucinogenics could change how the brain shoots off signals, according to scientists who gave mice a psychoactive substance.

After dosing mice with a drug similar to LSD, the researchers were surprised to find it reduced the activity in their visual cortex: a portion at the back of the brain that helps to process information taken in by the eyes.

The researchers hoped their findings, published in the journal Cell Reports, could help people with mental disorders for which hallucinations are a symptom, such as schizophrenia. While auditory hallucinations are more common in those with the disorder, some 27 percent of patients experience visuals that aren't real. Other debilitating symptoms include psychosis and delusions.

Cris Niell, a lead author of the study and an associate professor at the Institute of Neuroscience at the University of Oregon, commented: "You might expect visual hallucinations would result from neurons in the brain firing like crazy, or by mismatched signals. We were surprised to find that a hallucinogenic drug instead led to a reduction of activity in the visual cortex."

"In the context of visual processing, though, it made sense," he explained. "Understanding what's happening in the world is a balance of taking in information and your interpretation of that information. If you're putting less weight on what's going on around you but then overinterpreting it, that could lead to hallucinations."

To investigate how the brain responds to psychoactive drugs, the researchers gave mice a substance called 4-iodo-2,5-dimethoxyphenyl isopropylamine (DOI). The drug behaves similarly to recreational drugs such as LSD and psilocybin (so-called magic mushrooms). Researchers monitored how DOI interacted with the serotonin-2A receptor, which is linked to hallucinations in drugs but also the brains of those with schizophrenia.

The team hooked up the mice to equipment so they could monitor the activity of their neurons after they took the drug, and as they were shown images.

Niell argued the study brings us a step closer to understanding the cause of hallucinations. Next, the team will investigate the visual cortex of mice in more detail. The research that was carried out on the mice, however, does not correlate directly to humans.

Last year, a separate study into hallucination investigated how high levels of dopamine could cause auditory hallucinations in people with schizophrenia.

Dr. Guillermo Horga, an assistant professor of clinical psychiatry at Columbia University Irving Medical Center and co-author of a study published in the journal Current Biology, commented at the time: "Our brain uses prior experiences to generate sensory expectations that help fill in the gaps when sounds or images are distorted or unclear.

"In individuals with schizophrenia, this process appears to be altered, leading to extreme perceptual distortions, such as hearing voices that are not there. Furthermore, while such hallucinations are often successfully treated by antipsychotic drugs that block the neurotransmitter dopamine in a brain structure known as the striatum, the reason for this has been a mystery, since this neurotransmitter and brain region are not typically associated with sensory processing."

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Researchers have given mice a hallucinogenic drug to investigate how it affects the brain. Their findings could help people with mental disorders for which hallucinations are a symptom, such as schizophrenia. Getty Images