What happens to the brain during hallucinations? Scientists gave mice drugs to find out

Hallucinogens could change the way the brain draws signals, according to scientists who administered a psychoactive substance to mice.

After administering a drug similar to LSD to the mice, the researchers were surprised to find that the latter reduced the activity of their visual cortex: a part located at the back of the brain that makes it possible to process the information collected by the patients. 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. Although auditory hallucinations are more common in people with the disease, approximately 27% of patients have visual effects that are not real. Other debilitating symptoms include psychosis and delusions.

Cree Niell, lead author of the study and associate professor at the Institute of Neuroscience at the University of Oregon, commented, "You could expect visual hallucinations resulting from neurons in the brain that are triggered like fools, or by mis-matched signals, surprised to find that a hallucinogenic drug had instead resulted in a reduction in the activity of the visual cortex. "

"In the context of visual processing, however, it made sense," he said. "Understanding what's going on in the world assumes a balance between taking information into account and interpreting it – if you give less importance to what's going on around you, but then over-interpreted, that could lead to to hallucinations. "

To study how the brain reacts to psychoactive substances, the researchers gave mice a substance called 4-iodo-2,5-dimethoxyphenyl isopropylamine (DOI). The drug behaves in the same way as recreational drugs such as LSD and psilocybin (called magic mushrooms). The researchers studied the interactions between DOI and the serotonin-2A receptor, related to hallucinations of drugs but also to the brain of those with schizophrenia.

The team linked the mice to the equipment so they could monitor the activity of their neurons after taking the drug and when they received images.

Niell argued that the study brings us closer to understanding the cause of hallucinations. The team will then examine in more detail the visual cortex of the mice. The research conducted on mice, however, is not directly correlated with humans.

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

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

"In people with schizophrenia, this process appears to be impaired, leading to extreme perceptual distortions, such as voices that do not exist, and even though these hallucinations are often successfully treated with drugs. antipsychotics that block the dopamine neurotransmitter in a brain structure known as a striatum, the reason is mysterious because this neurotransmitter and this brain region are not usually associated with sensory processing. "

The researchers administered a hallucinogenic drug to the mouse to study its impact on the brain. Their findings could help people with mental disorders for whom hallucinations are a symptom, such as schizophrenia. Getty Images